Microsoft Power Point - RFT-B9

© Alcatel 1

© All rights reserved. Passing on and copying of this document, use and communication of its contents not permitted without written

authorization from Alcatel.

Introduction to Radio Fine Tuning BSS release B9

TRAINING MANUAL3FL10493ACAAWBZZA ed 2 – November 2005

© Alcatel 2

Safety Warning

Both lethal and dangerous voltages are present within the equipment. Do not wear conductive jewelry while working on the equipment. Always observe all safety precautions and do not work on the equipment alone.

Caution

The equipment used during this course is electrostatic sensitive. Please observe correct anti-static precautions.

Trade Marks

Alcatel and MainStreet are trademarks of Alcatel.

All other trademarks, service marks and logos (“Marks”) are the property of their respective holders including Alcatel. Users are not permitted to use these Marks without the prior consent of Alcatel or such third party owning the Mark. The absence of a Mark identifier is not a representation that a particular product or service name is not a Mark.

Copyright

This document contains information that is proprietary to Alcatel and may be used for training purposes only. No other use or transmission of all or any part of this document is permitted without Alcatel’s written permission, and must include all copyright and other proprietary notices. No other use or transmission of all or any part of its contents may be used, copied, disclosed or conveyed to any party in any manner whatsoever without prior written permission from Alcatel.

Use or transmission of all or any part of this document in violation of any applicable Canadian or other legislation is hereby expressly prohibited.

User obtains no rights in the information or in any product, process, technology or trademark which it includes or describes, and is expressly prohibited from modifying the information or creating derivative works without the express written consent of Alcatel.

Alcatel, The Alcatel logo, MainStreet and Newbridge are registered trademarks of Alcatel.

All other trademarks are the property of their respective owners. Alcatel assumes no responsibility for the accuracy of the information presented, which is subject to change without notice.

© 2004 Alcatel. All rights reserved.

Disclaimer

In no event will Alcatel be liable for any direct, indirect, special, incidental or consequential damages, including lost profits, lost business or lost data, resulting from the use of or reliance upon the information, whether or not Alcatel has been advised of the possibility of such damages.

Mention of non-Alcatel products or services is for information purposes only and constitutes neither an endorsement nor a recommendation.

Please refer to technical practices supplied by Alcatel for current information concerning Alcatel equipment and its operation.

© Alcatel 3

Contents

1 TYPICAL RADIO PROBLEMS 15

2 ALGORITHMS AND ASSOCIATED PARAMETERS 46

3 OTHER ALGORITHMS 194

4 ALGORITHMS DYNAMIC BEHAVIOR 238

5 CASE STUDIES 267

6 ANNEX 288

© Alcatel 4

Page intentionally left blank

© Alcatel 5

All rights reserved © 2004, Alcatel

1 TYPICAL RADIO PROBLEMS

© Alcatel 6

6@Introduction to Radio Fine TuningBSS Release B9


1 TYPICAL RADIO PROBLEMS Session presentation

> Objective: to be able to characterize typical radio problems in order to trigger an intervention of the appropriate team

> Program:

1.1 Theoretical presentation

1.2 Coverage problem

1.3 Interference problem

1.4 Unbalanced power budget problem

1.5 TCH Congestion problem

1.6 Deducing the right team for intervention

1.7 Exercises

S1: TYPICAL RADIO PROBLEMS

S2: ALGORITHMS AND ASSOCIATED PARAMETERS

S3: OMC-R RADIO PARAMETERS

S4: ALGORITHMS DYNAMIC BEHAVIOR

S5: CASE STUDIES

© Alcatel 7




Theoretical presentation

Coverage problem

Interference problem

Unbalanced power budget problem

TCH Congestion problem

Deducing the right team for intervention

Exercises

© Alcatel 8



> Several sources of information can alert RFTM team:

• QoS indicators

• Customers complaints

• Drive tests

• Other teams information (NSS statistics)

> As many symptoms are common to several causes, it can be necessary to:

• Consolidate standard sources of information

• Carryout specific examinations

• Deduce the appropriate team for intervention

1.1 Theoretical presentation Justification

© Alcatel 9



1.2 Coverage problem


Coverage problem





Exercises

© Alcatel 10



> Definition: Bad coverage

• A network or cell facing coverage problems presents a bad RxLevand RxQual in the same time on some areas.

> Symptoms:

• Customers complain about dropped calls or/and “no network”

• OMC QoS indicators

– TCH failure rate

– Call drop rate

– Low proportion of better cell HO

– High rate of DL quality HO

• A interface indicators

– High rate of Clear Request messages, cause radio interface failure

1.2 Coverage problem Definition and symptoms

> No information is available on non-covered parts of the network, as there are non-mobiles making calls over there!

> Nevertheless, cells in border of non-covered zones do have a particular behavior:

> Cell A will mainly perform Better Cell handovers towards its neighbors, whereas cell B, bordering the non-coverage area, will perform emergency handovers for MSs exiting the network.

• For these MS, mainly DL Quality HO will be triggered:

– DL because MS antenna is less efficient than BTS one,

– Quality rather than Level since Qual has a greater priority in Alcatel HO causes.

AB

© Alcatel 11



> Depending on the information sources you have:

• Radio Measurement Statistics (RMS) –

– (RxLevel , RxQuality) matrix

– Radio Link Counter S vector

– Number of calls with DL/UL bad coverage (bad RxLev, bad RxQual)

• Abis interface (for example with COMPASS)

– bad quality > 5%

– bad level RxLev < - 95 dBm and RxQual > 4

• OMC-R or A interface

– unexpected high traffic, induced by call repetition

• Billing information

– High recall rate detected

1.2 Coverage problem Examination

> RMS: new PM type in B7

• Provides statistics from any area in the network which are available at any time.

• Cost-effective.

• Easier and cheaper to perform than Drive test or Abis Trace.

• The operator can tune 54 parameters (based on RxLev, BFI, C/I, Radio Link Counter S, Path Balance, etc.) to define up to 16 templates (depending on cell type – rural, urban, etc. – for example).

• Trigger from the OMC-R.

• NPA can save up to 15 days of RMS for the complete network.

• Templates can be designed in RNO.

• Result reports are available in RNO and NPA.

© Alcatel 12



> If the actual coverage is not the one predicted by RNP tools

– check antenna system

– increase or decrease antenna down-tilt

– check BS_TXPWR_MAX

– to be increased if value different to RNP power budget

> If the actual coverage is OK compared to the predicted ones

– indoor traffic, to be handled by specific means

– if black spot close to cell border, ease outgoing HO

1.2 Coverage problem Typical causes

© Alcatel 13



> Example of an Abis trace analysis

1.2 Coverage problem Investigation with Abis trace (1/2)

Frequenc

y

RxLev_U

L

RxLev_D

L

RxQual_UL Path_loss_U

L

Path_loss_D

L

delta_Path_lossDelta_quality AV_MS_PWRNb_of_sample

s

RxQual_DL

Frequenc

y

Qual0 Qual1 Qual2 Qual4 Qual5 Qual6 Qual7 Bad_QualityQual3

Frequenc

y


119 -89.29 -84.67 0.42 123.82 123.67 0.15 -0.01 34.53 30740.43

92 -89.77 -89.09 0.41 124.87 128.09 -3.21 0.03 35.11 10 2530.38

111 -83.15 -79.15 0.17 116.05 121.22 -5.16 -0.16 32.9 53390.33

DISTRIBUTION OF UPLINK QUALITY

119 86.50% 3.19% 2.50% 1.92% 2.08% 0.98% 0.26% 3.32%2.57%

92 88.11% 1.82% 1.91% 2.14% 2.17% 1.15% 0.19% 3.51%2.51%

111 77.70% 4.30% 4.30% 3.56% 3.56% 1.70% 0.17%4.36%

119 88.29% 1.82% 2.05% 1.30% 1.46% 1.76% 0.94% 4.16%2.37%

92 87.50% 2.98% 2.60% 2.11% 1.14% 0.74% 0.50% 2.38%2.43%

111 71.30% 3.82% 4.02% 4.16% 4.30% 4.23% 3.16%4.89%

DISTRIBUTION OF DOWNLINK QUALITY

5.43%

11.73%

> It could have been coverage problems if this trace was made for 3 mono-TRX cells. In this case, the 3 lines are uncorrelated. Anyway, delta path loss of frequency 111 is greater than 5dB, showing a problem on this TRX.

> If this is a 3-TRX cell, it cannot be a coverage problem as the three TRXs are not impacted. It will be either interference or malfunction of one TRE.

> If the trace is done on 3 mono-TRX cells, in that case, it could be a coverage problem. Be careful when interpreting this result table: even if average levels in the UL and the DL are high and a lot of Quality problems are seen, nobody can say that samples with bad quality have a good level ! The level seen is just an average…

> One should have a look to the next slide…

© Alcatel 14




1.2 Coverage problem Investigation with Abis trace (2/2)

Thresholds

Bad Coverage

– RxLev ≤ -95

- RxQual > 4

Interference

– RxLev > -95

– RxQual > 4

3-88.006

3-95.333

1-71.003

1-80.006

1-80.003 -80.003

5

7

11

1

1212

Number_UL: 10 253

Number_DL: 10 253

Int_UL: 2

BC_UL:

358Int_DL: 0%

0.02%

3.49%

67-

104.64

20

48-

107.50

51

Number_UL: 5339

Number_DL: 5339

Int_UL: 0

BC_UL:

290Int_DL: 0%

BC_DL:

626

0.00%

5.43%

Samples<Lev>BSIC

63-

101.54

2

Samples<Lev>BSICNeigh_Cell_N

b

Samples<Lev>BSICNeigh_Cell_N

b

<RxLev_Serving>= -102.17 dBm3.74%BC_DL:

115

57-

100.53

20

45-98.71210

34-98.0365

33-98.6137

<RxLev_Serving>= -106.56 dBm

BC_DL:

244

2.38% <RxLev_Serving>= -106.17 dBm

Frequency: 92

Frequency: 111

11.73

%Neigh_Cell_N

b10

> All samples are Bad Coverage samples (BC). None is interference, showing that this cell is not facing any interference problem.

> By the way, if the cell is mono-TRX, this is a coverage problem.

> If the cell is 3 TRXs, this is a malfunction of the TRE (shown also by the high value of delta_path_loss).

© Alcatel 15



> Suspecting a cell coverage problem

• Distribution of samples per RxQual value and RxLev band

• Distribution of samples per RxLev band

1.2 Coverage problem Investigation with RMS (1/2)

0

1

2

4

5

7

[-110,-104[

[-104,-98[

[-98,-92[

[-92,-86[

[-86,-80[

[-80,-74[

[-74,-68[

[-68,-62[

[-62,-56[

[-56,-47[

RxQuality (Nb)

RxLevel(dB)

[0, 14 793]

]14 793, 23 446]

]23 446, 29 586]

]29 586, 34 348]

]34 348, 38 239]

]38 239, 41 529]

]41 529, 44 378]

]44 378, 46 892]

Out of RangeX

Interval of numberof samples

Downlink Samples Matrix in log scale

3

6

Not acceptable coverage limit:too low level too bad quality

> A coverage problem is observed when a significant amount of the traffic of a cell is suffering from both low level and bad quality (RxQual).

> To confirm, distribution of samples per RXLEV band should be also considered to know the proportion of calls which are experiencing a low signal level.

> If a lot of samples of low level and bad quality are observed for only a sub-part of the TRXs (can be one only) then a BTS hardware problem or a problem on the antennae should be suspected.

> If all the TRXs are experiencing a lot of samples of low level and bad quality then a coverage problem must be suspected.

> These RMS indicators are provided on RNO tool per TRX, per Cell:

• Matrix of Number of Measurement Results per DL RxQual value and per DL RxLev bandRMQLDSAM = RMS_DL_RxQuality_RxLevel_sample

• Vector of Percentage of Samples per DL RxLev bandRMQLDLVDV = RMS_DL_RxLevel_distrib

• Vector of Percentage of Samples per DL RxQual bandRMQLDQUDV = RMS_DL_RxQuality_distrib

© Alcatel 16



> Suspecting a cell coverage problem

• Average TA values per RxQual value and RxLev band

1.2 Coverage problem Investigation with RMS (2/2)

16.00%

14.00%

12.00%

10.00%

8.00%

6.00%

4.00%

2.00%

0.00%

01/12/2001

01/01/2002

02/01/2002

03/01/2002

04/01/2002

05/01/2002

06/01/2002

07/01/2002

08/01/2002

09/01/2002

10/01/2002

11/01/2002

12/01/2002

13/01/2002

14/01/2002

10

9

8

7

6

5

4

3

2

1

0

%N > TA thres TA max

Maximum Timing Advance and TA > threshold

N > TA thresTA maxTA threshold

0

1

2

4

5

7

[-110,-104[

[-104,-98[

[-98,-92[

[-92,-86[

[-86,-80[

[-80,-74[

[-74,-68[

[-68,-62[

[-62,-56[

[-56,-47[

RxQuality (Nb)

RxLevel(dB)

[0, 2]

]2, 4]

]4, 6]

]6, 8]

Out of Range

Interval of averageTiming Advance

Uplink average TA Distribution

3

6

X

Acceptablecoverage limit:

sufficient level andgood quality

Not acceptablecoverage limit:too low level andtoo bad quality

% of TA valueover TA thresholdhas also to beconsidered

> In order to know if the coverage problem is due to a big amount of traffic at the cell border or rather to indoor calls, the average TA value per RXQUAL value and RXLEV band as well as the Percentage of TA values over TA threshold should be observed.

• Matrix of Average TA per UL RxQual value and per UL RxLev bandRMQLUTAM = RMS_UL_RxQuality_RxLevel_TimingAdvance

• Rate of Measurements Results whose TA is greater than the TA thresholdRMTAGTR = RMS_TimingAdvance_greater_threshold_rate

• Maximum TA value of all values reported in Measurement Results RMTAMXN = RMS_TimingAdvance_max

© Alcatel 17



1.3 Interference problem


Coverage problem





Exercises

© Alcatel 18



> Definition: Interference

• A network facing interference problems presents good RxLev and bad RxQual in the same time on some areas.

> Symptoms

• Customers complain about bad speech quality (noisy calls) and/or call drops


– SDCCH/TCH Drop

– Low proportion of better cell HO

– High rate of DL/UL quality HO and interference HO

– Low HO success rate



1.3 Interference problem Definition and symptoms

> DL/UL depends on the way on which the interference is present.

> Mainly, interferences are in the DL, due to bad frequency planning introducing interferences in the network. And this problem will not change till the frequency plan is not returned…

> Sometimes, interference can be in the UL in very dense area (for example, microcell area), since MSs are very close.

> Finally, sometimes interferences are not coming from BS or MS but from another radio equipment, either in the UL or the DL.

© Alcatel 19



> Radio Measurement Statistics (RMS)

– RxQual/RxLev matrix

– CFE/RxLev matrix

– C/I vectors for neighbors

– C/I vectors for MAFA frequencies

– MAFA is a new standardized GSM feature for mobiles

– MAFA mobiles can provide C/I measurements from

non-neighbor cells

– Number of calls with DL/UL interference (good RxLev, bad RxQual)

– Number of noisy calls (bad RxQual) with bad voice quality (bad FER)

– A high rate use of the most robust AMR codecs also denounce interferences problems . But be careful, this can also be due to a pessimistic choice of the thresholds used for codec change.

1.3 Interference problem Examination with RMS (1/3)

> The feature Radio Measurement Statistics (RMS) is designed to make far easier the work for planning and optimization of the network by providing the operator with useful statistics on reported radio measurements.

> In fact these statistics give directly the real cell characteristics by taking into account the MS distribution.

> Thanks to this feature, the operator is able to:

• detect interfered frequencies.

• assess the quality of the cell coverage.

• detect and quantify cell unexpected propagation.

• assess the traffic distribution in the cell from statistics on reported neighboring cells.

• evaluate the voice quality in the cell.

• etc.

> In regards to the “RTCH Measurements Observation” (measurement type 11), the Radio Measurement Statistics (RMS) bring the following advantages:

• smaller report files.

• the report files always have the same maximum length whatever the measurement duration is.

• every measurement is taken into account (no sampling).

• no more need for measurement post-processing tools for statistics. Directly available with RNO or NPA.

© Alcatel 20



> Suspecting a cell interference problem

• Number of samples per RxQual value and RxLev band


Quality problems are obvious at any

level of RMS data

� Interference highlighted

� Network fine tuning needed

0

1

2

4

5

7

[-110,-104[

[-104,-98[

[-98,-92[

[-92,-86[

[-86,-80[

[-80,-74[

[-74,-68[

[-68,-62[

[-62,-56[

[-56,-47[

RxQuality (Nb)

RxLevel(dB)

[0, 14 793]

]14 793, 23 446]

]23 446, 29 586]

]29 586, 34 348]

]34 348, 38 239]

]38 239, 41 529]

]41 529, 44 378]

]44 378, 46 892]

Out of RangeX


Downlink Samples Matrix in log scale

3

6

Average DL RxQuality = 2.81

Average RxQual value per RXLev bandhas also to be considered

0

1

2

3

4

5

6

[-110,

-104[

[-104,

-98[

[-98,

-92[

[-92,

-86[

[-86,

-80[

[-80,

-74[

[-74,

-68[

[-68,

-62[

[-62,

-56[

[-56,

-47[

RxQuality (Nb)

RxLevel

(dB)

Downlink average RxQuality per RxLevel

RxQuality

Average

© Alcatel 21



> Suspecting a Voice Quality problem

• Number of samples per BFI band and RxLev band


[0, 1[

[1, 2[

[2, 4[

[6, 8[

[8, 10[

[14, 18[

[-110,-104[

[-104,-98[

[-98,-92[

[-92,-86[

[-86,-80[

[-80,-74[

[-74,-68[

[-68,-62[

[-62,-56[

[-56,-47[

CFE (Nb)

RxLevel(dB)

[0, 14 793]

]14 793, 23 446]

]23 446, 29 586]

]29 586, 34 348]

]34 348, 38 239]

]38 239, 41 529]

]41 529, 44 378]

]44 378, 46 892]

Out of RangeX


Consecutive Frame Erasure Matrix in log scale

[4, 6[

[10, 14[

[14, 18[

[14, 18[

0

1

2

3

4

5

6

[-110,-104[

[-104,-98[

[-98,-92[

[-92,-86[

[-86,-80[

[-80,-74[

[-74,-68[

[-68,-62[

[-62,-56[

[-56,-47[

Average CFE

RxLevel (dB)

Uplink average Consecutive Frame Erasure per RxLevel

7

8

Average RxQual

0

1

2

3

4

5

6CFEAverage

RxQualityAverage

Consecutive Frame Erasure (BFI) is a

measurement based on loss of consecutive

speech frames over one SACCH mw.

It is directly linked to Voice Quality.

RxQual to be compared with CFE since Bad

RxQual does not always mean bad VQ.


• Matrix of Number of Measurements Results per CFE band (or BFI band) and per UL RxLev band RMFEM = RMS_UL_ConsecutiveFrameErasure_RxLevel_sample

• Vector of Average number of Consecutive Frame Erasure per UL RxLev bandRMFEBFAV = RMS_UL_ConsecutiveFrameErasure_avg_per_RxLevel

• Vector of Average UL RxQual per RxLev bandRMQLUQUAV = RMS_UL_RxQuality_avg_per_RxLevel

© Alcatel 22



> GSM interference

– co-channel

– adjacent

> Non GSM interference

– other Mobile Networks

– other RF sources

1.3 Interference problem Typical causes

© Alcatel 23



> Adjacent channel interference

– +6 dB are sufficient to interfere (9 dB according GSM)

1.3 Interference problem GSM interference: adjacent channel (1/2)

Level

Frequency

F(BTS1)

6 dB

F(BTS2)

F(BTS1) = F(BTS2)+1

© Alcatel 24



> Adjacent channel interference:

• Symptom

– Usually downlink interference

– High rate of quality HO, call drop (due to HO but mainly due to radio) and TCH assignment failure

• Examination

– Neighbor cells in Abis trace (only for BCCH)

– Non-neighbor cells in RMS (MAFA frequencies)

– Frequency planning C/(I adjacent) < -6 dB

• Correction

– Downtilt increase of interferer, or even change of antenna orientation

– Reduction of BS power if necessary, Change of frequency (best solution)

– Concentric cell implementation (1 extra TRX needed if traffic cannot be supported by Outer+Inner configuration)

1.3 Interference problem GSM interference: adjacent channel (2/2)

© Alcatel 25



> GSM Interference

• Co-Channel interference

– -12 dB are sufficient (-9 dB according GSM)

1.3 Interference problem GSM interference: co-channel (1/2)

Level

Frequency

F(BTS1)

-12 dB

F(BTS2)

F(BTS1) = F(BTS2)

© Alcatel 26



> Co-channel interference

• Symptom

– Usually downlink interference

– High rate of quality HO, call drop and call failure

• Examination

– Neighbor cells in Abis trace (only for BCCH)

– Non-neighbor cells in RMS (MAFA frequencies)

– Frequency planning C/I < 12 dB

• Correction

– Downtilt increase of interferer, or even change of antenna orientation

– Reduction of BS power, Change of frequency

– Concentric cell implementation (1 extra TRX needed if traffic cannot be supported by Outer+Inner configuration)

1.3 Interference problem GSM interference: co-channel (2/2)

© Alcatel 27



> GSM interference: µcellular

• BTS1: ARFCN 5

• BTS2: ARFCN 6

• MS1 indoor

– RxLev_UL: - 90 dBm

• MS2 outdoor, connected to BTS2

– 1: no level on BTS1(BTS 1 under-roof)

– 2: - 80 dBm on BTS1:interferer UL/DL

– 3: no level on BTS1

– µcell algo prevents BTS2->BTS1 HO

1.3 Interference problem GSM interference: µcellular

MS 1(indoor)

MS 2

(outdoor)1

2

3

BTS 1

(Micro)

BTS

2

> When interferences are created by frequency plannig, it’s not so hard to detect them. But frequency planning tools mainly consider DL C/I and coverage.

> Some problems are more difficult to predict. For example, let’s consider a microcell layer:

• A and B are 2 microcells with the coverage described before in dense urban environment.

• Even if both cells A & B are using adjacent frequencies (5 and 6), the overlapping area is far from cell A antenna. Thus, in this area C/I is lower than 6 dB.

• A “red” MS is connected on cell A. When the MS starts its call, it transmits full power and a PC algorithm quickly reduces MS power as the received level is very good (microcell coverage). When MS A enters the building, it faces a loss of signal of 20 dB. Then, MS power increases to MS_TXPWR_MAX.

• A second mobile “B” is connected to cell B and moves down in the coverage area of cell B. MS power of B decreases quickly down to MS_TXPWR_MIN as the MS is close to the antenna. But when MS B arrives outside the building where A is sitting, A and B are close and transmitting on adjacent frequencies… Then B has to increase its power to avoid dropping its call. By the way, global level of freq B is increased in all cell B… creating interference in the UL.

A

B

© Alcatel 28



> GSM Interference: Forced Directed Retry

• The MS should connect to cell2, but no TCH available

• The MS connects to cell 1 with forced directed retry

• The MS is emitting at high level (far from BTS1)

– UL interference for BTS 3

• BTS 1 is emitting at high level

– DL interference at BTS 3

1.3 Interference problem GSM interference: Forced Directed Retry

Cel l 2 : 45

Ce ll 3 : 23

Cell 1: 2

4

MS

BTS

2

BTS

1

BTS

3

> Another more difficult case of interference: FDR

• When examining the preceding situation of planning tool: no problem of C/I. No risk of interference.

• The FDR algorithm allows an MS connected on an SDDCH on a cell without any free TCH to make an SDCCH-TCH handover (cause 20) so that it takes a TCH on its neighbor. As seen from the user, this is not a handover (call establishment phase, no impact on speech quality), and this algorithm is very efficient to avoid cell congestion cases.

• This algorithm is mainly based on neighbor level compared to parameter L_RXLEV_NCELL_DR (n). If the level greater than this threshold, the TCH is to be seized on neighbor.

• FDR is mandatory for dual layer or dual band networks (and very easy to configure in this case), since we have capture handovers. Capture handovers send traffic to lower or preferred band cells. In case these cells are congested, calls may not be established, even if upper or non-preferred band cells are free (due to MS idle mode selection, advantaging microcell for example). With the FDR algorithm, the MS takes an SDCCH in the preferred cell, and FDR is used to take a TCH on the non-preferred cell in case of congestion. This situation highlights a good network behavior, since the MS is at the same time in the coverage area of both cells (preferred and not preferred).

> The situation described on the slide corresponds to the usage of FDR in a single layer network. This is in that case a heavy-to-tune algorithm presenting of lot of interference and bad quality call risks, since the mobile will be connected to a cell when being not in its service area.

umbrella

microcell

FDRcapture

© Alcatel 29



> Other mobile networks: TACS/AMPS/NMT900

– Inter-modulation with GSM BS/MS receiver

– spurious RACH for AMPS (AMPS Tx bands close to GSM uplink band)

– examination

– TASC: coverage hole with 600 m from TASC BTS

– AMPS => 50% reduction of range if AMPS/GSM BTS collocated

> Other RF interferers (Radar, shop anti-theft mechanisms, medical device ...)

1.3 Interference problem Non-GSM interference

> Other RF interferers:

• medical devices: GSM equipments disturb them more than the opposite !

• anti-theft mechanisms.

• Example:

• The Microcell is showing a very high call drop rate. On one frequency, very small call duration.

• No problem seen in the frequency plannig. No potential interferer.

• Abis trace:

• The Spectrum analyzer connected on the antenna feeder highlights a peak on GSM freq 6 in the UL…

• Anti-theft mechanism turned off: no more problem…

shop

Microcellantenna

Qual

Level

Qual

Level

DL UL

interference

© Alcatel 30



1.4 Unbalanced power budget problem


Coverage problem





Exercises

© Alcatel 31



> Definition: Unbalanced power budget

• A cell facing unbalanced power budget problems presents a too high path-loss difference between UL and DL (often DL>UL)

• Rule: try to have delta as small as possible to avoid access network possible only in 1 direction (usually BTS->MS: OK and MS->BTS: NOK)

> Symptoms:


– High rate of Uplink quality Handover causes

– Low incoming HO success rate (no HO Access triggered on the uplink)

– Degradation of TCH failures and OC call drop indicators



• O&M Alarms

– Voltage Standing Wave Ratio BTS Alarm (VSWR)

– TMA Alarm (in case of G2 BTS or Evolium BTS with high power TRE)

1.4 Unbalanced power budget problem Definition and symptoms

> UL Quality HO is triggered:

• UL since the problem is in the UL.

• Quality as Quality has greater priority than level.

© Alcatel 32



1.4 Unbalanced power budget problem Examination

> Examination

• RMS –

– Path Balance vector per TRX

– Number of calls with abnormal bad FER (good RxQual & bad FER)

• Abis monitoring:

– |delta path-loss| > 5dB

– Check if problem is occurring for 1 TRX or all

> Problem on 1 TRX: FU/CU or TRE problem or ANY problem or cables connected to this equipment.

> All TRXs: problem on antenna, feeder, jumper or common equipment (ex: ANX, ANC).

© Alcatel 33




1.4 Unbalanced power budget problem Abis trace

106 -94.52 -87.19 0.43 127.55 130.19 -2.64 0.18 33.03 20660.25

Frequenc

y


Frequenc

y


89 -84.29 -75.17 0.65 115.32 118.17 -2.85 0.21 31.03 20010.44

118 -90.75 -83.36 0.46 123.22 126.36 -3.14 0.04 32.46 31930.41

124 -88.89 -85.30 0.29 120.48 128.30 -0.37 31.59 29310.67

DISTRIBUTION OF UPLINK QUALITY

106 84.75% 4.07% 3.68% 1.36% 1.50% 0.92% 0.53% 2.95%3.19%

89 81.41% 1.70% 2.95% 6.35% 2.55% 1.30% 0.10% 3.95%3.65%

118 83.62% 4.23% 4.23% 1.57% 1.79% 0.97% 0.25%3.35%

106 90.27% 3.44% 2.08% 0.92% 1.36% 0.34% 0.05% 1.74%1.55%

89 80.16% 6.45% 7.00% 1.50% 0.50% 0.45% 0.10% 1.05%3.85%

118 86.78% 2.72% 3.95% 1.41% 1.13% 1.19% 1.00%1.82%

DISTRIBUTION OF DOWNLINK QUALITY

3.01%

3.32%

Frequenc

y

RxLev_U

L

RxLev_D

L

RxQual_UL Path_loss_U

L

Path_loss_D

L

delta_Path_lossDelta_quality AV_MS_PWRNb_of_sample

s

RxQual_DL

-7.82

124 90.79% 1.06% 2.18% 1.77% 1.30% 0.48% 0.07%2.35% 1.84%

124 77.14% 4.37% 5.87% 3.48% 1.36% 0.82% 1.02%5.94% 3.21%

Example of Computation of delta path loss based on Abis measurements

BTS transmitted power 45,4 MS transmitted power 33

combiner loss -4,4

measured received DL level -93 measured received UL level -98

DL Path loss 134 UL path loss 131

delta path loss computed on Abis -3 dBm

© Alcatel 34



> Suspecting a TRX hardware problem

• Average Path Balance

• Fair average Path Balance at Cell level can hide a bad value for one TRX

1.4 Unbalanced power budget problem RMS data

0

500

1000

1500

2000

2500

3000

[-110,-20[

[-20,-10[

[-10,-6[

[-6,-3[

[-3,0[

[0,3[

[3,6[

[6,10[

[10,20[

[20,110[

Nb Samples

PathBalance(dB)

NbSamples

PathBalance Distribution

Average Cell Path Balance = - 0.9 dB


• Vector of the Number of Measurement Results per Path Balance bandRMPBV = RMS_PathBalance_sample

• Average Path Balance valueRMPBAN = RMS_PathBalance_avg

© Alcatel 35



> Antennae or common RF components, TMA (pb common to all TRXs of the BTS)

> TRX RF cables/LNA ... if problem located on only 1 FU

1.4 Unbalanced power budget problem Typical causes

> Every BTS has its proper architecture and the diagnosis must be adapted.

© Alcatel 36



1.5 TCH Congestion problem


Coverage problem





Exercises

© Alcatel 37



1.5 TCH Congestion problem Definition and symptoms

> Definition: TCH Congestion

• TCH Congestion rate (TCH Assignment Phase) is too high (more than 2%)

• Rule: try to meet the offered traffic (asked by users) by providing the right number of resources (TRX extension)

> Symptoms:

• Customers complain about ‘Network busy’


– High “TCH Congestion rate”

– Low “incoming Intra/Inter BSC HO success rate” (no TCH available)

– High “Directed Retry rate” if activated

• A interface indicator: “BSS Congestion failure in OC”

– High rate of Assignment Failure messages, No radio resource available

© Alcatel 38



1.5 TCH Congestion problem Examination and typical causes

> Examination: TCH Congestion

• On a per cell basis examination, check the evolution of the TCH Congestion rate.

> Typical causes:

• Special events:

– Foreseeable: football match, important meeting

– Activate some TRXs already installed (and use Synthesized FH)

– Add special moving BTSs

– Not foreseeable: car crash on the highway

> Cells on wheel operational by several operators around the world for special events coverage & capacity

• IRMA (SFR) connected to Caen’s BSC.

• Orange coverage / Football WC 1998 for Paris « Stade de France »:

– Specific cells covering Paris Stadium. During games, only small capacity (using joker frequencies). During breaks, some TRX off cells around are turned off, and frequencies are reused for stadium cells.

© Alcatel 39



1.5 TCH Congestion problem Typical causes (1/2)

• Daily periodic problems

– At peak hour, the cell is not correctly dimensioned.

Hardware solution (refer to Annex 1)

– Estimate the offered traffic:

At OMC-R level: Traffic in Erlang/(1- TCH Congestion rate)

– Use the B-Erlang law to estimate the number of TCHs required for a 2% blocking rate, thus the target configuration

– Add TRXs to reach the new target configuration and find ‘joker frequencies’ and / or implement concentric cells.

Annex 1

> Warning: “offered traffic” is not the capacity delivered by the system but the traffic asked by the users.

© Alcatel 40



1.5 TCH Congestion problem Typical causes (2/2)

> Daily periodic problems

– At peak hour, the cell is not correctly dimensioned.

Software solution

– Use specific densification features

» Half Rate

» Forced Directed Retry

» Traffic handover

» Fast Traffic handover

» Candidate Cell Evaluation (FREEFACTOR / LOADFACTOR)

> Half rate may not only mean “SW” solution. Need of G2 BSC/TC, Evolium TRE or G2 DRFU.

© Alcatel 41



1.6 Deducing the right team for

intervention


Coverage problem





Exercises

© Alcatel 42



1.6 Deducing the right team for intervention Process

Problem characterization

Make assumption causes

Check the tuning of default radio parameters

Consult the config. db Choose an (other) classical algo

Identify the tunable parameters

Impact estimation

Standard setting ?

No

Yes

Yes

No

No

Yes

Call expert

- Microcell, multiband- Concentric

=N

No

Yes

No

Yes

No

Yes

Parameters modificationDatabase updating

Impact simulation of aparameter modification

No

- Hopping- Marketing

Yes

QOS alarm on the network,on a BSC or some cells

- Indicators (% call drop)- Field measurements/planning- Subscriber complains

QOS team

DHCPEND

Drive test team

DHCPEND

Dimensionning team

OK

Correctionaction

Maintenance team

Planning team

NOK

Cell corrected ?Neighbor cell ?

RFT team - Interferences- Coverage (indoor)- Power budget- Congestion (TCH, SDCCH)- BSS problemInvestig problem ?

Planning/BSS causes

Standard parameters ?

Onpurpose

Systemproblem ?

SimulationOK ?

Recurrent problem ?

N times

Check ?With QOS ?

© Alcatel 43



1.6 Deducing the right team for intervention Coverage problem

> Coverage problem:

• If the field reality does not match the RNP prediction

– Maintenance team to change physical configuration (tilt, azimuth, antenna height, etc.) and drive test team to check it

• If the field reality matches the RNP prediction

– Deployment team to add sites (tri-sector, micro cellular, indoor cells)

© Alcatel 44



1.6 Deducing the right team for intervention Others problems

> Interference problem:

• Planning team to identify the interference source and correct it(joker frequency, new frequency planning, etc.)

> Unbalanced power budget problem:

• Maintenance team to check the impacted BTS (Antennae, TMA, RF cables, LNA, diversity system, etc.)

> TCH Congestion problem:

• Traffic team (theoretically always in relation with the marketing team) to manage the need of TRX extension, densification policy,etc.

© Alcatel 45



1. Typical radio problems Training exercise

Time allowed:

10 minutes

High rate of UL QUAL HO

causes

Good RxLev and Bad

RxQual

VSWR alarm (OMC-R)

(Voltage Standing Wave Ratio)

Bad RxLev and Bad RxQual

OMC QOS indicators:

% TCH ASS failure high

% call drop high

% QUAL HO

% call drop

% call failure

Unbalanced

Power BudgetBad coverage Interferences

TCH

Congestion

High Path-loss difference

between UL and DL

Low incoming HO success

rate

© Alcatel 46


2 ALGORITHMS AND ASSOCIATED PARAMETERS

© Alcatel 47



2 ALGORITHMS & ASSOCIATED PARAMETERS Session presentation

> Objective: to be able to describe the Power control and Hand-over algorithms and list the associated parameters

> Program:


2.2 Radio measurements principles

2.3 Averaging windows and book-keeping

2.4 Radio Link Supervision and Power control

2.5 Handover Detection

2.6 Handover Candidate Cell Evaluation

2.7 Handover Management

2.8 Exercise





S5: CASE STUDIES

© Alcatel 48


2 ALGORITHMS AND ASSOCIATED

PARAMETERS



Radio measurements principles

Radio measurements data processing

Radio Link Supervision and Power control

Handover Detection

Handover Candidate Cell Evaluation

Handover Management

Exercise

© Alcatel 49



JUSTIFICATION

When the detected problem does not concern another team (Networkplanning and frequency planning, Dimensioning, Radio engineering, Maintenance) or

when the other teams cannot give any solution (too tight frequency planning, no additional TRX available, no financial budget for new sites, etc.)

the Radio Fine Tuning team has to find a compromise between:

– High traffic density (Erl/km²/Hz)

– High quality of service (Call drop, CSSR, Speech quality, indoor, etc.)

Its role: take charge of radio resources management process

> This process can be fully described by Power Control and Handover algorithms.

� In-depth knowledge of these algorithms is required for tuning

2.1 Theoretical presentation Justification

© Alcatel 50


2 ALGORITHMS AND ASSOCIATED

PARAMETERS

2.2 Radio measurements principles





Handover Detection


Handover Management

Exercise

© Alcatel 51



2.2 Radio measurements principlesRadio measurement mechanisms (1/2)

> MS connected (TCH or SDCCH)

> The serving cell gives the MS the list of the neighbor cells to listen to

> Every SACCH, the MS reports to the serving cell: measurement report message

• Received level of 6 best cells(which can change)

• DL level and qualityof serving cell

B

est c

ellBe

st cell

B

est ce ll Bes t ce ll

C e ll

C e ll

Best cell

Cell

Best cell

Servin

g cell

SYS_INFO_5message (list)

MS reporting

> The BTS sends a SYS_INFO_5 message that contains the list of neighbor cells for connected mode. (The SYS_INFO_2 message contains the list of neighbor cells for idle mode).

• Sys info 2bis, 2ter, 5bis and 5ter are also used for multiband networks.

• MS reporting depends on EN_INTERBAND_NEIGH and on MULTIBAND_REPORTING parameters. The MS may report:

– 6 strongest cells of any band (MULTIBAND_REPORTING=0), or

– 5 strongest cells of the serving band + 1 strongest cell of another band (MULTIBAND_REPORTING=1), or

– 4+2 (MULTIBAND_REPORTING=2), or

– 3+3 (MULTIBAND_REPORTING=3).

> RXLEV

• Range: [-110dBm, -47dBm]

• Binary range: [0, 63]; 0=-110dBm, 63=-47dBm

• The higher the physical or binary value, the higher the receiving level

> RXQUAL

• Range: [0.14%, 18.10%]

• Binary range: [0, 7]; 0=0.14%, 7=18.10%

• The lower the physical or binary value, the lower the bit error rate, the better the quality

• 0-2=excellent; 3=good; 4=ok; 5=bad; 6=very bad; 7=not acceptable

© Alcatel 52



> For each MS connected to the BTS (TCH or SDCCH)

• UL received level and quality is measured every SACCH

• The Timing Advance (TA) is computed

• The UL information is gathered into the measurement report

• This is the message result sent by the BTS to the BSC

• The BSC is computing algorithms

• usually using average value (sliding window) of these measurements

2.2 Radio measurements principlesRadio measurement mechanisms (2/2)

BSC

MS

DL me

asurements

U

L+DL measurements

BTS

Measurementreport

Measurementresult

Candidate cellevaluation

MeasurementsActive channelpreprocessing

Candidate cellevaluationHO & PCdecision

Candidate cellevaluation

PC execution

HO execution

> The BTS starts sending MEASUREMENT RESULT messages as soon as it receives the RL ESTABLISH INDICATION message from the MS.

> The BTS stops sending MEASUREMENT RESULT messages upon receipt of one of the two following messages:

• DEACTIVATE SACCH

• RF CHANNEL RELEASE

> Every SACCH multiframe, the BTS:

• receives the MEASUREMENT REPORT message from the MS. For power control and handover algorithms, this message contains downlink measurements and, in the layer 1 header, the power used by the MS.

• does uplink measurements.

• reports the uplink and downlink measurements to the BSC in the MEASUREMENT RESULT message.

• Input flows

– Uplink radio signal: radio signal received on the Air interface.

– BS_TXPWR_CONF: BS transmit power currently used by the BS.

– DTX_DL: indicator of downlink DTX use.

• Output flows

– Abis MEASUREMENT RESULT message

• Internal flows

– Radio measurements:

– Air MEASUREMENT REPORT message (DL) containing DL MS radio measurements.

– Uplink radio measurements (quality and level) and a flag indicating whether DTX was used in the downlink (DTX/DL).

– Timing advance: last TA calculated by the BTS.

– MS_TXPWR_CONF: last reported value of MS power (reported by the MS).

– BS_TXPWR_CONF: value of the BS transmit power currently in use.

– BFI_SACCH: bad frame indicator of the SACCH block produced every SACCH multiframe (# 480ms):

– 0 = SACCH frame successfully decoded

– 1 = SACCH frame not successfully decoded

© Alcatel 53



2.2 Radio measurements principlesStructure of a measurement result

CHAN_NUMBER_IEID

FREQ(5) / BSIC(5) / RXLEV_NCELL(6)

Meas_result_number_IEID

Meas_result_number

Element Identifier

Length

{2} / RXLEV_UL_SUB_

{2} / RXQUAL_UL_FULL / RXQUAL_UL_SUB

BS_POWER_IEID

{3} / BS_POWER

Element Identifier

MS_TXPWR_CONF / R{3}

TOA / R{2}

Element Identifier

Length

Length

BA_USED / DTX_UL / RXLEV_DL_FULL

0 / MEAS_VALID / RXLEV_DL_SUB

0 / RXQUAL_DL_FULL / RXQUAL_DL_SUB / NO_NCELL_M

NO_NCELL_M / RXLEV_NCELL(1)

FREQ(1) / BSIC(1)

BSIC(1) / RXLEV_NCELL(2)

RXLEV_NCELL(2) / FREQ(2) / BSIC(2)


RXLEV_NCELL(3) / FREQ(3) / BSIC(3)


0 / Message Type{7}

RXLEV_NCELL(5) / FREQ(5)


SACCH_BFI / DTX_DL{1} / RXLEV_UL_FULL

CHANNEL_NUMBER


MSG_TYPE

MSG_DISK

TI {4} / Prot. Disc{4}


FREQ(6) / BSIC(6)

L1 Info

L3 Info:

Measurement

report from

the MS

> Basically, the MEASUREMENT RESULT message is composed of:

• L1 info: SACCH Layer 1 header containing MS_TXPWR_CONF and TOA.

• L3 info: MEASUREMENT REPORT from the MS. This message contains the downlink measurements and neighbor cell measurements.

• Uplink measurements performed by the BTS.

• BTS power level used.

> SUB frames correspond to the use of DTX

• if the mobile is in DTX, the rxlevsub or rxqualsub is used to avoid measuring the TS where there is nothing to transmit in order not to distort measurements.

• else rxlevfull is used that is to say all TSs are measured.

> MS TXPOWER CONF: which is the actual power emitted by the MS.

> TOA is timing advance.

> SACCH BFI: bad frame indicator; 2 values 0 or 1; 0 means that the BTS succeeded in decoding the measurement report.

> How the neighbor cells are coded:

• BCCH1 index in BA list / BSIC1; BCCH2 index in BA list / BSIC2

• why? because it does not receive LAC/CI (too long ) but BCCH and replies with BCCH/BSIC

© Alcatel 54



> Extended Measurement Reporting mechanisms

• Extended Measurement Order includes the MAFA frequencies the MS is asked to measure

• EMO sent once to the MS on SACCH after TCH seizure

• Extended Measurement Results include the average signal level measured on each MAFA frequency over one SACCH mf duration

• EMR received once per call on SACCH

2.2 Radio measurements principlesExtended Measurement Reporting (EMR)

Channel Activation Acknowledge

Assignment Request

Physical Context Request

Physical Context Confirm

Channel Activation (TCH)(EMO included)

TCH ESTABLISHMENT

TCHAssignment Complete

Assignment CompleteAssignment Complete

SACCH

SACCH

SACCH

SACCH

SACCH (EMO)

(MAFA Freq. List)

SACCH (EMR)

(MAFA Freq. RxLev)

TCH ASSIGNMENT (OC or TC)

MS BTS BSC MSC

> When the BTS receives a CHANNEL ACTIVATION with the Extended Measurement Order (EMO) included, it must send this information on the SACCH to the corresponding mobile only once.

> When the BTS has to send this information, it must replace the sending of system information 5, 5bis, 5ter or 6 by this information. At the next SACCH multiframe, the BTS must resume the sending of this system information by the replaced one.

> The EMO must be sent after 2 complete sets of SYS_INFO5 and 6, i.e. after the 2nd SYSINFO 6 after the reception of SABM. This guarantees the MS has received a complete set.

> Then, the BTS normally receives from the MS an EXTENDED MEASUREMENT RESULT with the level of the frequencies to monitor. The BTS must make the correlation between these levels and the frequencies contained in the latest EMO information, after having decoded them, according to the order of the ARFCN. The ‘EXTENDED_MEASUREMENT_RESULT’ is NOT forwarded to the BSC, instead a ‘MEASUREMENT_RESULT’ with indication ‘no_MS_results’ is sent to the BSC.

> In particular, the BTS must identify the level of the BCCH frequency of the serving cell (which must always be part of the frequencies to monitor) and apply it as the RXLEV_DL in the Radio Measurement Statistics. The other frequencies will be considered in the same way as the BCCH frequency of neighbor cells: they will be linked to the neighbor level and C/I statistics.

© Alcatel 55



Time allowed:

5 minutes

• (BSIC, BCCH index)/(LAC, CI) problem

– As LAC and CI information take up too much space, the MS only reports the decoded BSIC and the BCCH index when it sends measurement on the adjacent cell

– The BSC makes the correspondence between the couple (BSIC, BCCH index) and the real neighbor cell concerned [completely defined by (LAC,CI)]

– WHAT IS THE RISK?

2.2 Radio measurements principlesTraining exercise (1/2)

© Alcatel 56



2.2 Radio measurements principlesTraining exercise (2/2)

> Explain why cell 2 has a very high outgoing HO unsuccessful rate and a high call drop

Cell 2

Cell 1

Cell

(7, 62)

CI=1964GSM900

Cell 3

CI=6169GSM900

(7, 62)

(3, 46)

Cell

CI=6169GSM900

© Alcatel 57



2.3 Radio measurements data processing





Handover Detection


Handover Management

Exercise

© Alcatel 58



2.3 Radio measurements data processingFunctional entities

BSC

Active ChannelPre-processing

BTS

Radio LinkMeasurements

Assignment of radio measurements data processing functions in the ALCATEL BSS

> The active channel pre-processing function calculates average values of signal levels, qualities and timing advance provided by the radio link measurements function.

> The pre-processing is based on a sliding window averaging technique. The averaging is either weighted or unweighted depending on the type of the input parameters.

© Alcatel 59



> Active channel pre-processing

• ACTIVATED EACH TIME A MEASUREMENT IS RECEIVED

• AVERAGING VALUES OF SIGNAL LEVELS, QUALITIES, TIMING ADVANCE

– USING “SLIDING WINDOW” TECHNIQUE

• BUILDING A BOOK-KEEPING LIST OF NEIGHBOR CELLS

– The MS is reporting the 6 best cells at one time

– They can change from 1 measurement to another

– Maximum for 1 call: last 32 best ones (among 64 maximum declared as neighbor)

2.3 Radio measurements data processingActive channel pre-processing

© Alcatel 60



> Active channel pre-processing – Principles

• HANDLED by the BSC

• ACTIVATED when the BSC receives:

– ESTABLISH INDICATION from the MS on SAPI 0, or

– HANDOVER FAILURE from the MS, or

– ASSIGNMENT FAILURE from the MS (in case of intracellhandover)

• STOPPED when a HANDOVER COMMAND is emitted in the serving BSC

• AVERAGING VALUES OF SIGNAL LEVELS, QUALITIES, TIMING ADVANCE

– USING “SLIDING WINDOW” TECHNIQUE

• BUILDING A BOOK-KEEPING LIST OF NEIGHBOR CELLS

2.3 Radio measurements data processingActive channel pre-processing - Principles

> The pre-processing function is stopped when a HANDOVER COMMAND is emitted by the serving BSC. At this time, the MEASUREMENT RESULT messages are ignored by the pre-processing function and no update of the book-keeping tables or averaging is done anymore.

> The pre-processing function is enabled again (in case of failure of an intracell or intercell handover) after reception of either messages listed above, and the old measurements are kept in the book-keeping list and taken into account in the new averaging.

> The pre-processing function is completely handled by the BSC. The input parameters of this function are provided by the BTS every SACCH multiframe in the MEASUREMENT RESULT message.

> The function calculates average values of levels, qualities and timing advance. The pre-processing method is based on a sliding window averaging technique. The pre-processing is done for every measurement sample, i.e. every SACCH multiframe. The averaging intervals are expressed in terms of SACCH multiframe periods and their range is between 1 and 31.

> The averaging process for any variable can start as soon as A_YYYY_XX (YYYY stands for “LEV”, “QUAL”, “PBGT” or “RANGE”and XX for “HO”, “DR”, “PC” or “MCHO”) samples, each with MEAS_VALID bit set to 0 (validity indicator reported by the MS in the MEASUREMENT REPORT message), are actually available except in case of the averaging of the received level from the neighbor cells and the averaging of AV_RXLEV_PBGT_HO, AV_BS_TXPWR_HO and AV_BS_TXPWR_DR.

© Alcatel 61



> Avoid reacting too early to some “atypical” measurement(s)

2.3 Radio measurements data processingMeasurement averaging (1/2)

75.00

80.00

85.00

90.00

95.00

100.00

105.00-------

> The calculation of levels, qualities and timing advance (i.e. distance information) uses a variety of averaging window sizes as well as specific weighting factors for quality estimates.

> One separate window exists for:

• power control on the uplink and the downlink (A_LEV_PC , A_QUAL_PC),

• emergency handover (A_LEV_HO , A_QUAL_HO , A_RANGE_HO),

• fast emergency handover for microcells (A_LEV_MCHO),

• better cell handover and better zone handover (A_PBGT_HO) for intra-layer, interlayer and interzone handovers,

• forced directed retry (A_PBGT_DR),

• neighbor filtering and ranking for all HOs (A_PBGT_HO),

• codec adaptation (A_QUAL_CA_HR_FR , A_QUAL_CA_FR_HR).

© Alcatel 62



> Objective: average measurements to avoid reacting to transient degradation

• Principle: sliding window: level/quality/distance values are averaged for N last samples

N = A_LEV_HO samples for uplink and downlink levelN = A_QUAL_HO samples for uplink and downlink qualityN = A_RANGE_HO samples for distanceN = A_PGBT_HO for level used in power budget equation

• Example (A_LEV_HO=6, A_QUAL_HO=4, A_PBGT_HO=8)

• Experiences• some experiments have shown that the number of HOs is very sensitive to modification of these values

2.3 Radio measurements data processingMeasurement averaging (2/2)

DL Level

AV-RxLevAV-Lev-

PGBTDL QualAV-RxQual

1 2 3 4 5 6 7 8 9 10 11 1

2

1

3

1

4

15 16 1

7

18 1

9

2

0

21 2

2

23 2

4

Meas

2 3 3 4

3

7

4

-

957

5

-

99

-90 -

92

-93 -

98

-

100

-

98

-90 -80-

97

-96 -94

-95 -947 5 2

6 7 5

-

75

-72 -71 -110 -70

-

90

-86 -81 -83 -80

-

92

-89 -86 -87 -83

1 1 0 6 0

4 2 1 2 2

-69-78

-800

2

-68 -78 -88 -95-77 -78 -81 -78

-77 -77 -78 -810 0 1 2

2 0 0 1

-

98-

83-

853

2

-100-110-110-88 -95 -100

-83 -88 -936 7 7

3 5 6

-110-104

-997

7

> At BSC level,

• Input flows

– MEASUREMENT RESULT

• Control flows

– active channel pre-processing configuration parameters for PC:

– A_LEV_PC, W_LEV_PC, A_QUAL_PC and W_QUAL_PC,

– active channel pre-processing configuration parameters for HO:

– A_LEV_HO, W_LEV_HO, A_PBGT_HO, W_PBGT_HO, A_QUAL_HO, W_QUAL_HO, A_RANGE_HO, A_LEV_MCHO, W_LEV_MCHO, A_PBGT_DR.

– cells list for book-keeping:

– BA_IND_SACCH: indicator of the change of the BA_allocation,

– NBR_ADJ: number of declared adjacent cells of the serving cell denoted by n,

– for n=1 to NBR_ADJ: BSIC(n) and FREQ(n).

• Output flows

– Averaged measurements for power control:

– AV_RXQUAL_UL_PC ; AV_RXLEV_UL_PC: MS power control/threshold comparison,

– AV_RXQUAL_DL_PC ; AV_RXLEV_DL_PC: BS power control/threshold comparison.

– Averaged measurements for handover detection:

– AV_RXQUAL_UL_HO, AV_RXQUAL_DL_HO, AV_RXLEV_UL_MCHO,

– AV_RXLEV_UL_HO, AV_RXLEV_DL_HO, AV_RXLEV_DL_MCHO,

– AV_LOAD , averaged traffic load

– AV_BS_TXPWR_HO, AV_RANGE_HO,

– AV_RXLEV_PBGT_HO, AV_RXLEV_NCELL(n), AV_RXLEV_NCELL_BIS(n).

– AV_RXLEV_PBGT_DR,

– AV_RXLEV_NCELL_DR(n), n=1..BTSnum.

– BFI_SACCH

– AV_RXQUAL_xx_CA_HR_FR, AV_RXQUAL_xx_CA_FR_HR

– MS_TXPOWER_CONF / BS_POWER: last power level reported by the MS and transmit power currently used by the BS.

© Alcatel 63



> BUILDING A BOOK-KEEPING LIST OF NEIGHBOR CELLS

– The MS reports the measurements of the NO_NCELL_M (≤6) best cells every multi-frame

– The adjacent cells reported by the MS can change from one measurement to another

– The book-keeping function keeps a table of the last 32 reported adjacent cells

– Clearing process of non-reported neighbors during 10s (signal level=0)

2.3 Radio measurements data processingneighbor cell measurement book-keeping

> An MS is required to measure the BCCH power level of a number of BCCH frequencies. These measurements are used for the power budget computation in the BSC and the candidate cell evaluation in the BSC.

> The MS reports to the BTS, in the MEASUREMENT REPORT message, the measurements of the NO_NCELL_M (NO_NCELL_M <= 6) best cells it receives (RXLEV_NCELL, BCCH frequency index and BSIC number) for each multiframe. In case of multiband capability, the mobile reports the best cells of each supported frequency band (if available). This reporting is allowed at BSS level by the flag EN_INTERBAND_NEIGH and it is specified by the parameter MULTIBAND_REPORTING.

> The adjacent cells reported by an MS can change over the averaging interval. The book-keeping function keeps a table composed of the last 32 reported adjacent cells, the maximum number of which is NBR_ADJ. The total number of adjacent cells for which measurements reported by the MSs are available within the average interval is BTSnum.

> The BSC G1 maintains a table of up to 150 cells, from which up to 64 can be declared as adjacent cells to a given cell.

> The BSC G2 maintains a list of up to 1000 cells, from which up to 64 can be declared as adjacent cells to a given cell.

> Because the maximum number of adjacent cells may be greater than 32, the number of adjacent BCCH frequencies is limited to 32. Moreover, a mechanism for overwriting obsolete entries in the bookkeeping table, when new cells are reported, is provided.

> When the variable BTSnum reaches its maximum value of 32 and at least one new cell has to be entered in the list, then the BSC sorts out all cells in the bookkeeping list, which have been reported with signal level = 0 for the last 20 measurements (10 seconds).

> This is done by summing the raw measurement values over the last 20 samples. All the corresponding cell entries are cleared from the bookkeeping list, BTSnum is decreased by the number of cleared entries and some of the vacant entries are used to include the new cells.

The end of the comment is on the next page...

© Alcatel 64



2.3 Radio measurements data processingTraining exercise

> Measurements averaging

• With ‘averaging window’excel sheet...

• Compute averaging on quality,distance and level

• Make charts with different slidingaveraging windows

Time allowed:

10 minutes

Raw measurements

Average measurements

AV_RXLEV_DL_HO

A_LEV_HO=8

A_LEV_HO=2

2 3 4 5 6 7 8 9 10 11 12 13 14 151-75

-80

-85

-90

-95

Number ofmeasurements

Level

AV_RXQUAL_DL_HO

3

A_QUAL_HO=8

A_QUAL_HO=2

2 3 4 5 6 7 8 9 10 11 12 13 14 151

4

3

2

1

0

Quality

AV_RANGE_HO

10

12

15

A_RANGE_HO=8

A_RANGE_HO=2

2 3 4 5 6 7 8 9 10 11 12 13 14 151

25

20

15

10

5

Distance

DL Level

A_LEV_HO=8

A_LEV_HO=4

A_LEV_HO=2

DL Level

A_QUAL_HO=8

A_QUAL_HO=4

A_QUAL_HO=2

DL Level

A_RANGE_HO=8

A_RANGE_HO=4

A_RANGE_HO=2

-80

2

10

-78

2

11

-84

3

9

-87

3

11

-80

2

13

-75

1

12

-77

4

14

-94

4

15

-79

3

16

-77

1

17

-78

2

18

-84

3

17

-89

3

19

-90

3

20

-91

4

19

DL Level

DL Quality

Distance

-80

-76

-82

-82

-86

-82

-81

-87

-82

-82

-78

-81

-82

-78

-81

-80

-81

-82

-82

-87

-84

-85

-90

-85

-89

-91-81

-82

-86

-82

-84

-82

-78-79

A_LEV_HO=4



3

2

3

3

2

3

3

3

3

3

3

4

3

3

4

3

3

4

3

3

2

3

3

2

3

3

2

2

3

32 3

A_QUAL_HO=4 3

13

14

16

13

16

17

15

17

18

15

17

18

16

18

18

17

19

20

18

19

20

11

12

11

13

13

13

14

11 10

A_RANGE_HO=4 10

> Fill up the table with average function. The chart will be automatically processed

> The fact that there may not be enough cleared entries to store new measurements is excluded, see justification below:

> Because the MS must resynchronize at most every 10s with the neighbor cells it monitors, it is useless to keep cells in the bookkeeping list which have not been reported for more than 10s, it will be impossible to makkes an handover towards these cells.

> Therefore, the overwriting mechanism described above will function correctly if there are less than 32 cells reported in every 10s, which makes an average rate of 3 new cells per second.

> The potentiality of overflow of the book-keeping list is therefore excluded.

> The book-keeping is performed according to the BSIC and BCCH frequency couple. This function updates the table every multiframe except if the measurement report is missing or Measurement Valid Bit is set to not valid. When the level of a cell is not reported, a zero must be entered as measurement value. For each multiframe and for each of the NO_NCELL_M cell measurements it receives, the function has to check the BSIC number and the BCCH frequency index (FREQ(n)).

> When the couple (BSIC, BCCH frequency) is not in the reference list (received from the OMC), the corresponding measurements should be discarded.

> The BTSnum variable is updated every multiframe except if the measurement report from the MS is missing. It is incremented by the number of new couples (BSIC number, BCCH frequency index) registered as described above.

> Remark: Two cells can have the same BSIC number or the same BCCH frequency index. Therefore, the couple of these parameters is needed to define a cell.

© Alcatel 65



2.4 Radio Link Supervision and Power Control





Handover Detection


Handover Management

Exercise

© Alcatel 66



2.4 Radio link supervision and power controlFunctional entities

BSCBTS

Radio LinkSupervision

PC CommandPC ThresholdComparison

Radio LinkCommand



Assignment of PC functions in the ALCATEL BSS

> The two main functions specified in this document and implemented in the ALCATEL BSS are:

• Radio link supervision and radio link command:

– These functions handle the detection of the radio link failure so that calls which fail either from loss of radio coverage or unacceptable interference are satisfactorily handled by the network. The radio link supervision is responsible for detection of the loss of the radio link, based on incorrectly received SACCH frames. The radio link command is responsible for commanding to set the power at a maximum level for radio link recovery or to clear the call when the radio link has failed.

– The radio link recovery can be activated or not, depending on a configuration flag (EN_RL_RECOV). The radio link failure procedure is always running and clears the call when the radio link has failed.

• Power control:

– This function handles the adaptive control of the RF transmit power from the MS and the BS. The RF power control aims at minimizing the co-channel interference and also at reducing the DC power consumption of the MS. This function is in charge of detecting a need for a power command and then of applying this power command. Therefore it can be divided into two processes: PC threshold comparison and PC command. MS and BS power control are operating independently, they can be activated or not, depending on configuration flags (EN_MS_PC and EN_BS_PC).

> All these functions require directly or indirectly input parameters provided by the function in charge of the radio link measurements.

> Most of the input data required by the power control functions are provided by Active channel pre-processing function.

> The figure depicts in a general way:

• the interconnections between all these functions,

• the implementation of these functions in the ALCATEL BSS.

© Alcatel 67



> Principles

• Detection (by BTS) of a radio link failure with an MS

– notification to BSC for radio resource release

• Try to recover an MS when radio becomes poor

– optional mechanism “radio link recovery”

– by requiring BTS and MS to transmit at maximum power

• Equivalent mechanism in MS for Radio Link Failure detection

2.4 Radio link supervision and power controlRadio link supervision

> The determination of the radio link failure is based on a counter. According to the GSM Technical Specification 05.08 for the BSS, the criterion for incrementing/decrementing this counter should be based:

• either on the error rate on the uplink SACCH,

• or on RXLEV/RXQUAL measurements of the MS.

> In the ALCATEL BSS, it is based on the number of SACCH frames which cannot be decoded.

> It must be stressed that this criterion is related to the first one recommended above but it is not exactly the same. The ALCATEL criterion is in fact the one recommended by the GSM Technical Specification 05.08 for the MS.

© Alcatel 68



2.4 Radio link supervision and power controlPrinciples of radio uplink supervision

> For each active radio channel, a counter “S” is• decremented by 1 each time an SACCH frame cannot be decoded

(BFI=1)• incremented by 2 each time a valid SACCH frame is received

> The value of S gives a measure of the “quality” of uplink radio link> Initial value of S = BS_RADIO_LINK_TIMEOUT

• if S reaches N_BSTXPWR_M, a radio link recovery is triggered optional)• if S reaches 0, a radio link failure is detected

> RADIOLINK_TIMEOUT_BS ≥ RADIOLINK_TIMEOUT is important because the mobile must release the radio channel first.

M SBT

S

Coun te r S Coun te r S '

R LTO_BS(B S_R AD IO _L IN K _T IM EOU T )

18

16R LTO (T 100)

(R AD IO _L IN K _ T IM EO UT )

N _B STXPW R_M

13R ad io lin kR ec ove ry

SA CCH b locklo st: - 1

SA CCH b lo ckrec e ived : + 2

0 0R ad io lin kFa ilu re

> The radio link supervision function is performed in the BTS and it uses three parameters given to the BTS in the TRX configuration data message:

• EN_RL_RECOV: flag enabling/disabling the sending of CONNECTION FAILURE INDICATION by the BTS when the need for radio link recovery is detected,

• N_BSTXPWR_M: threshold for the radio link recovery,

• RADIOLINK_TIMEOUT_BS: threshold (number of SACCH messages) for the radio link failure.

> In addition, the function handles a counter named S. RADIOLINK_TIMEOUT_BS is the initial and maximum value of S.

• For each SACCH not decoded, S is decremented by 1 while for each SACCH decoded, it is incremented by 2. The incrementation or decrementation is performed if the following condition is met: RADIOLINK_TIMEOUT_BS >= counter S >= 0.

• As soon as the counter S is equal to the threshold N_BSTXPWR_M, the radio link recovery is triggered if EN_RL_RECOV = ENABLE. Therefore, in the case where the shadowing is so strong that all SACCH frames are lost, the radio link recovery will be triggered after (RADIOLINK_TIMEOUT_BS - N_BSTXPWR_M) SACCH periods.

> The parameter N_BSTXPWR_M must be set according this simple behavior.

> If the radio link recovery is not successful, as soon as S reaches 0, the radio link failure procedure is applied.

> As soon as a radio link failure is detected, the radio link supervision must be started again in the BTS.

© Alcatel 69



2.4 Radio link supervision and power controlS counter for radio link supervision

SACCHnumber

S value

2928272625242322212019181716151413121110987654321

0

5

10

15

20

25

RADIO_LINK_TIMEOUT_BS

N_BSTXPWR_M

SBFI

S = f [ BFI (t) ]

> Received events

• Activate supervision: activation of the radio link supervision from the BTS telecom layer 3,

• SACCH, BFI = 1: not decoded SACCH frame,

• SACCH, BFI = 0: decoded SACCH frame,

– Note: the BFI flag is internal to the BTS and does not deal with the BFI flag defined by the GSM.

• Deactivate supervision: deactivation of the radio link supervision by the BTS telecom layer 3.

> Transmitted events

• Radio link recovery: indication sent to the radio link command function in order to set the BS and MS powers to the maximum.

• Radio link failure: indication sent to the radio link command function in order to release the call.

> These events are sent to the BSC in the CONNECTION FAILURE INDICATION message:

• In case of Radio link recovery, the BTS sends only once (to avoid overload of the Abis interface) the CONNECTION FAILURE INDICATION message to the BSC with cause "set MS/BS-TXPWR-M” (value: '001 1111', reserved for National use). This action (message formatting) is performed by the GSM layer 3.

• In case of Radio link failure, the BTS sends the CONNECTION FAILURE INDICATION message with cause 'Radio link Failure' to the BSC.

> Thus, the CONNECTION FAILURE INDICATION message on Abis is not showing any call drop. One should look at the cause of CONFAIL.

© Alcatel 70



> The BTS is sending a Connection Failure Indication message

– cause ‘001 1111’ reserved for national usage (ALCATEL: RLR)

– On K1205: “set MS/BS_TXPWR_MAX (Alcatel only)”

> The BSC is sending BS and MS POWER CONTROL messages

– required for maximum possible values

– The MS required level is embedded in the SACCH header in the downlink

> Optional mechanism

– EN_RL_RECOV =ENABLE

– useless without power control

– “master” vs. power control

2.4 Radio link supervision and power controlRadio link recovery

> The action consists in increasing the power of the MS and of the BTS to their maximum, in a single step, if the link is failing, i.e. the BTS is not able to decode the SACCH anymore for some period of time.

> This functionality is performed upon reception of the CONNECTION FAILURE INDICATION message (cause “set MS/BS-TXPWR-M”) from the BTS. This message can be sent by the BTS only if EN_RL_RECOV = ENABLE. Upon reception of this message, the radio link command function:

1. sends to the BTS a power increase command up to BS_TXPWR_MAX (BS_TXPWR_MAX_INNER if the MS is on the inner zone of a concentric or multiband cell) in the BS POWER CONTROL message.

2. sends to the MS a power increase command up to min(MS_TXPWR_MAX,P) (min (MS_TXPWR_MAX_INNER,P) if the MS is in the inner zone of a concentric or multiband cell) in the message MS POWER CONTROL.

> When a radio link recovery occurs, the radio link command function gives an indication to the power control function once the power increase has been commanded.

> The maximum power increase of the MS is 2dB per 60 ms. Thus, if MS_TXPWR_MAX=33dBm and MS_TXPWR_MIN=13dBm, the MS coming from MIN to Max will take 600 ms.

Note: the BS Power Control process does not interfere with the recovery procedure since the former comes to a halt when no SACCH multiframe is received. Thus, the BS power control process does not take into account the radio link recovery event.

© Alcatel 71



> Radio link failure

• The BTS is sending a Connection Failure Indication message

– Cause ‘radio link failure’

• The BSC is notifying the loss to the MSC

– Usually Clear Request “radio interface failure”

• The BSC is releasing locally the radio resource (TCH or SDCCH)

– Radio frequency Channel Release message sent to BTS

• The call is dropped !

2.4 Radio link supervision and power controlRadio link failure

> The task of the radio link command consists in informing the call control function to release the call.

> Concentric cell or multiband cell

> The power value BS_TXPWR_MAX_INNER is applied in case of radio link recovery for an MS in the inner zone. The power value BS_TXPWR_MAX is applied in case of radio link recovery for an MS on an outer zone channel.

> Note: the radio link supervision procedure will function also if SACCH frames are not lost continuously, but with a longer reaction time.

© Alcatel 72



2.4 Radio link supervision and power controlRadio link supervision: training exercise

> With the “RLS” excel sheet...

• Taking into account themeasurements with BFI andthe parameter values (N_BSTXPWR_Mand RADIOLINK_TIMEOUT_BS)

• Indicate when

– A radio link recovery is triggered

– A radio link failure is triggered

Time allowed:

5 minutes

0

1

1

0

0

0

0

1

1

1

1

1

1

0

1

0

1

1

1

1

1

1

1

0

1

1

1

0

1

0

1

1

1

1

1

18

5

17

18

18

18

18

17

16

15

14

12

11

13

12

12

11

10

9

8

7

6

5

7

6

10

6

8

17

18

4

11

7

3

13 Radio Link Recovery

BFI S Action

Radio Link Supervision

N_NSTXPWR_MAXRLTO_BS

1318

Parameters:

© Alcatel 73



> Aims of Power control

• Reduce emitted power to the minimum possible

• Minimum power levels:

– GSM: 11dBm, 9dBm, 7dBm and 5dBm

– DCS: 2dBm, 0dBm

• Ensuring quality and received level of peer entity

• Adapted in real-time

• For Uplink PC: decrease UL interference and save MS battery

• For Downlink PC, decrease DL interference

2.4 Radio link supervision and power controlPower control

Output Power (dBm)GSM-900

Output Power (dBm)DCS-1800

Powerlevel

14

15

16

17

18

19

15

13

11

9

7

5

2

0

-

-

-

-

BTS MS

Uplink

RXLEV_UL

MS_TXPWRDownlink

BS_TXPWR

RXLEV_DL

> The main objective of the power control, in connection with handover algorithms, is to allow a maximum number of MSs to operate in the network while maintaining a minimum interference level.

> The algorithms must ensure that any mobile is connected with the cell in which the output powers from the MS and the BS are as low as possible (to reduce MS power consumption and interference in the network) while keeping a satisfactory link quality.

> When on a sufficient duration, the propagation conditions keep worsening, then action must be taken.

> The first action is to increase the output power levels at the MS or the BS. When the maximum allowed value has been reached, a handover may become necessary.

> To reflect this philosophy in macrocells (not in microcellular environment), the algorithm allows for handover on quality and strength reasons only when the last step of power control has been reached. If propagation conditions worsen rapidly when the MS is at low power, the power control algorithm allows to reach quickly the maximum power.

> Nevertheless great care must be taken in choosing the relative values of the thresholds for power control and handover as well as the averaging window sizes (smaller window size and higher threshold for power control than for handover). It must be remembered that, although it is desired that the MS transmits with the lowest possible power, it is more important not to lose acall. Thus early triggering for the power control is possible, by choosing, small values for the averaging window sizes and higher comparison thresholds.

© Alcatel 74



> Based on a threshold comparison mechanism

> Decrease emitted power when received level AND quality measured by peer entity are better than a given value

> Increase emitted power when the received level OR quality is lower than a given value

> Does not decrease power if the resulting level is below the low level threshold

� FEATURE REAL FAST PC GIVES REACTIVITY TO THE ALGORITHMS

2.4 Radio link supervision and power controlPower Control principles

> The threshold comparison process detects the need to change the MS power level. This detection is done by comparison between the averaged values produced by the active channel pre-processing function and thresholds.

© Alcatel 75



> MS Power control (for BS PC, replace MS by BS and UL by DL)

2.4 Radio link supervision and power controlPower Control detection

U_RXQUAL_UL_P

L_RXQUAL_UL_P

1

2

-95 -93 -85

L_RXLEV_UL_P

POW_RED_STEP_SIZE

U_RXLEV_UL_P

Quality

Level

-90 -75-94

3

> A need for a PC command is detected when one of the conditions above is true. Then, the information for the execution of the PC command is given to the ‘PC command’ process.

> The MS power control function can be disabled with a flag EN_MS_PC. This flag is changeable from the OMC-R.

Note: The GSM coding of quality is contra-intuitive, since the value 0 codes for the best quality and 7 for the worst. Thus, the comparison between two quality values must be understood in the opposite way in terms of quality.

Note: POW_RED_STEP_SIZE is used in two ways: for PC_COMMAND (decrease of MS power) and for PC_THRESHOD_COMPARISON (to avoid ping-pong effect).

© Alcatel 76



> Power increase: If

• AV_RXQUAL_UL_PC > L_RXQUAL_UL_P + OFFSET_RXQUAL_FH

• AV_RXQUAL_UL_PC ≤ L_RXQUAL_UL_P + OFFSET_RXQUAL_FHand AV_RXLEV_UL_PC < L_RXLEV_UL_P

Then PC_COMMAND(MS, INC, MS_P_INC dB, <min(MS_TXPWR_MAX, P))

> Power decrease: If

• AV_RXQUAL_UL_PC < U_RXQUAL_UL_Pand AV_RXLEV_UL_PC >= L_RXLEV_UL_P + POW_RED_STEP_SIZE

• AV_RXQUAL_UL_PC ≤ L_RXQUAL_UL_P + OFFSET_RXQUAL_FHand AV_RXQUAL_UL_PC ≥ U_RXQUAL_UL_P and AV_RXLEV_UL_PC > U_RXLEV_UL_P

Then PC_COMMAND(MS, RED, MS_P_RED dB, >MS_TXPWR_MIN)

2.4 Radio link supervision and power controlMS PC Threshold comparison

> OFFSET_RXQUAL_FH is an internal variable that is equal to 0 in case of Non-Hopping cell and OFFSET_HOPPING_PC in case of BBH or RH.

© Alcatel 77



> Power command philosophy:

• Target received level TARGET_RXLEV_UL

– middle threshold between U_RXLEV_UL_P and L_RXLEV_UL_P

• Adaptive power step size

– According to the average received level

– Limited power step size to MAX_POW_INC and MAX_POW_RED

– If only Quality problem: fixed power step size

– POW_INC_STEP_SIZE and POW_RED_STEP_SIZE

– Two weighting factors to modify the algorithm reactivity when level problem

– POW_INC_FACTOR for power increase

– POW_RED_FACTOR for power decrease

2.4 Radio link supervision and power controlMS Power Control Command

> Whenever any of the threshold conditions occurs, a PC command must be sent to the MS over the air interface.

> In order to compute the adaptive power step size, the middle threshold between the upper threshold U_RXLEV_UL_P and the lower threshold L_RXLEV_UL_P is considered.

> This threshold is regarded as the target received level around which the MS should always stay. The following algorithm tries tomaintain and bring the MS power closer to this target threshold. The size of the power step is limited to MAX_POW_INC for an increase of the MS power and MAX_POW_RED for a decrease of the MS power.

> When the received level is between the two thresholds U_RXLEV_UL_P and L_RXLEV_UL_P (i.e. no need to change the level) and a power control on quality cause is triggered, fixed power step sizes are applied: POW_INC_STEP_SIZE for power increase and POW_RED_STEP_SIZE for power decrease.

> Two weighting factors POW_INC_FACTOR (for power increase) and POW_RED_FACTOR (for power decrease) allow to modify the reactivity of the algorithm (the more POW_INC_FACTOR is nearby 1, the greater the reactivity of the algorithm is and the larger the power step size is).

> The target received level is TARGET_RXLEV_UL for the uplink path.

> TARGET_RXLEV_UL corresponds to the next higher multiple of 1 dB from (U_RXLEV_UL_P + L_RXLEV_UL_P)/2.

© Alcatel 78



2.4 Radio link supervision and power controlFast and Normal PC comparison

> Example

4800 960 1440 1920 2400

-110

-100

-90

-80

20 dB

Time(ms)

Power level(dB)

6 dB (POW_INC_STEP_SIZE)

4 SACCH =1 Measurement Report (MR)

MR 2 MR 3 MR 4

Need for PC Command detected

PC Command

Normal Power Control

Fast Power Control

© Alcatel 79



> PC_COMMAND (MS, INC, MS_P_INC dB, < power max)

• If MS_TXPWR < power max

then increase MS_TXPWR by min(MS_P_INC, MAX_POW_INC, powermax-MS_TXPWR)

• Where MS_P_INC is evaluated by the following algorithm:

if (AV_RXLEV_UL_PC < L_RXLEV_UL_P) (problem of level)

if (AV_RXQUAL_UL_PC ≤ L_RXQUAL_UL_P + OFFSET_RXQUAL_FH) (sufficient quality)

then MS_P_INC = roundup[ POW_INC_FACTOR* (TARGET_RXLEV_UL -AV_RXLEV_UL_PC)]

else MS_P_INC = roundup[ MAX ( POW_INC_FACTOR * (TARGET_RXLEV_UL - AV_RXLEV_UL_PC ), POW_INC_STEP_SIZE )]

else (problem of quality)

MS_P_INC = POW_INC_STEP_SIZE

2.4 Radio link supervision and power controlMS Power Increase Command computation

> In the equations:

• MS_TXPWR is the last MS_TXPWR_CONF value reported by the BTS.

• ‘roundup’ means ‘round to its next higher multiple of 2 dB’.

• ‘rounddown’ means ‘round to its next lower multiple of 2 dB’.

> The rate of change of MS power is required to be one nominal 2 dB step every 60 msec. Thus a 30 dB step change should be accomplished in 900 msec. The operator should be warned of this as it may impact on the choice of settings for MS_P_CON_ACK and MS_P_CON_INT.

> Then the ordered value of the MS transmit power, called MS_TXPWR, is sent to the MS as follows:

• The BSC sends the MS POWER CONTROL message to the BTS (i.e. to the TRX handling the relevant channel) which then forwards the PC command to the MS in the Layer 1 header.

• The MS applies the PC command and confirms this action by transmitting the applied power value (MS_TXPWR_CONF) on the uplink SACCH in the layer 1 header.

> On SACCH channel, the MS may not send the MEASUREMENT REPORT message (e.g. in case of transmission of Short Message).

• In this case, the BSC receives a MEASUREMENT RESULT message which does not contain the MEASUREMENT REPORT. The BSC takes into account the MS_TXPWR_CONF variable.

© Alcatel 80



> PC_COMMAND (MS, RED, MS_P_RED dB, > power min)

• If MS_TXPWR > power min

then decrease MS_TXPWR by min(MS_P_RED, MAX_POW_RED, MS_TXPWR- power min)

• Where MS_P_RED is evaluated by the following algorithm:

if (AV_RXLEV_UL_PC > U_RXLEV_UL_P) (good level)

if (AV_RXQUAL_UL_PC ≥ U_RXQUAL_UL_P) (sufficient quality)

then MS_P_RED = roundup[ MAX(POW_RED_FACTOR* (AV_RXLEV_UL_PC- TARGET_RXLEV_UL)), 2dB]

else MS_P_RED = roundup[ MAX ( POW_RED_FACTOR * (AV_RXLEV_UL_PC- TARGET_RXLEV_UL), POW_RED_STEP_SIZE )]

else (good quality)

MS_P_RED = POW_RED_STEP_SIZE

2.4 Radio link supervision and power controlMS Power Decrease Command computation

© Alcatel 81



> OFFSET_RXQUAL_FH

• This variable allows to take into account the frequency hopping in the RxQual evaluation (see Annex 2)

• Defined on a per cell basis

• Algorithm:

If Frequency hopping applied

– then OFFSET_RXQUAL_FH = Offset_hopping_PC

– Else OFFSET_RXQUAL_FH = 0

2.4 Radio link supervision and power controlFrequency Hopping cases

Annex 2

> In order to take into account the frequency hopping in the RXQUAL evaluation, the variable OFFSET_RXQUAL_FH is introduced.

> If on the corresponding channel, Frequency hopping is applied then OFFSET_RXQUAL_FH = Offset_Hopping_PC otherwise OFFSET_RXQUAL_FH = 0

> Offset_Hopping_PC is a parameter defined on a per cell basis.

> PC Downlink in Frequency hopping case

• In this case, the BSC inhibits the BS power control on all the channels which use the BCCH carrier. The entity performing the BS power control in the BSC gets all the information concerning a new channel and decides whether to activate the BS power control for this channel. The power control must be inhibited when the frequency used by the new channel is the same as the frequency used for the BCCH in the BTS (cell) in which the channel is activated.

• For any channel which has the BCCH frequency in its hopping sequence (MA), the MS is measuring a very good downlink level each time it hops on the BCCH. To avoid that this results in a too optimistic average, it is possible to require from the MS not to include the BCCH measurement in the averages. This is achieved by setting the PWRC flag to 1 in the SYSTEM INFORMATION type 6 message sent by the BSS on the SACCH.

• If the channel is hopping only on the BCCH frequency (after a transmitter failure), it is considered as a non-hopping channel and it is concerned by the non-frequency hopping case.

© Alcatel 82



> Timers

• T_SDCCH_PC allows the inhibition of PC on SDCCH

• When a new power is required, the confirmation is awaited:

– MS_P_CON_ACK

– BS_P_CON_ACK

• As soon as the new power is acknowledged, a fixed duration is awaited to trigger a new change of power, if necessary:

– MS_P_CON_INT

– BS_P_CON_INT

2.4 Radio link supervision and power controlPower Control timers (1/2)

> The timer T_SDCCH_PC allows to inhibit the MS and BS power control on SDCCH.

• This timer is changeable at the OMC-R level on a per cell basis. It is triggered upon receipt of the ESTABLISH INDICATION message after SDCCH activation for immediate assignment procedure. As long as the timer runs, the power control is inhibited on SDCCH.

• If the timer expires, the power control will be enabled again on SDCCH.

• If the timer is running at the sending of the RF CHANNEL RELEASE message, the timer is stopped.

> T_SDCCH_PC is useful in case of long SDCCH phases.

> During SDCCH for call establishment, PC disabled should be preferred with a view to secure call setup. Nevertheless, if SMS usage is very high, SDCCH phases may be long. In this case, to avoid interference, PC will be enabled after T_SDCCH_PC expiry (about 5s).

> After any PC command is sent to the MS, some time must be expected before MS_TXPWR_CONF (power confirmation sent by the MS on the uplink SACCH) can reach the desired value. The timer MS_P_CON_ACK is triggered after any power modification command to monitor that the desired transmission power MS_TXPWR is reached.

• If MS_P_CON_ACK elapses before the expected value of MS_TXPWR_CONF is received, the power control decision process is resumed immediately with the last MS_TXPWR_CONF received.

• If the expected value of MS_TXPWR_CONF is received before the timer MS_P_CON_ACK is elapsed, the timer MS_P_CON_ACK is stopped and the timer MS_P_CON_INT is triggered. Then the MS PC threshold comparison process is resumed with MS_TXPWR_CONF for the same MS as soon as MS_P_CON_INT expires.

© Alcatel 83



> IF xx_P_CON_ACK is expiring, it is a system problem:

• Wrong setting of xx_P_CON_ACK (too short)

• No reception of power command by the MS

– a radio link recovery can be activated

• Problem on Abis

– repetition of BS power command

> The expiry of P_CON_INT is a normal mechanism

2.4 Radio link supervision and power controlPower Control timers (2/2)

© Alcatel 84



> LEVEL and QUALITY USED in EQUATION are average ones with window size A_QUAL_PC and A_LEV_PC

> BS POWER CONTROL INHIBITED ON BCCH frequency

– BCCH must be emitted at the maximum level

> MS dynamic constraint

– minimum 2dB every 60 ms

> Emitted power can be changed by radio link supervision algorithm

– Radio link supervision has a greater priority

> Activation of power control can slow down HO decision

– some causes can be triggered only if the MS (BTS) is emitting at the maximum power

2.4 Radio link supervision and power controlExtra information

> Interaction with radio link command

• The MS power control function is informed of a radio link recovery by the radio link command function. Once the indication is received, the PC command process is resumed immediately:

– timer MS_P_CON_ACK is started (or reset and started if running),

– If MS_P_CON_ACK elapses before the expected value of MS_TXPWR_CONF is received, the power control decision process is resumed immediately with MS_TXPWR_CONF = min(MS_TXPWR_MAX,P).

> According to GSM Technical Specification 05.08 section 7.1, the BCCH carrier must be broadcast with a constant power in the cell. In this release of the ALCATEL BSS, this constant value is set to the maximum power allowed in the cell that is defined bythe parameter BS_TXPWR_MAX.

• This means that all dedicated channels (TCH, SDCCH) which are on the BCCH frequency must always be transmitted with the maximum power, i.e. the BCCH power must not be changed by the BS power control function.

© Alcatel 85



2.4 Radio link supervision and power controlPower Control: Training exercise (1/3)

> Power control UL

(Remark: Use the default parameters document)

• What happens if we do not use Frequency Hopping?

• Why is it better to have A_LEV_PC=A_LEV_HO/2?

• Thresholds:

– Lower QUAL of RX uplink = 3

– High QUAL of RX uplink = 2

– Lower LEV of RX uplink = -90dBm

– Upper LEV of RX uplink = -75dBm

– POW_RED_STEP_SIZE= 4

– POW_INC_STEP_SIZE= 6

• Put the right threshold in the next slide chart

Time allowed:

25 minutes

© Alcatel 86




> Power control UL

QUESTION

For each case:• PC triggered?• Step size value?

With POW_INC_FACTOR = 0,6and POW_RED_FACTOR = 0,6and MAX_POW_INC = MAX_POW_RED = 8

Quality

Level

Nb of case

AV RXQUAL UL PC

AV RXLEV UL PC

Power control

Delta value

1 2 3 4 5 6

0 1 2 6 3 4

-98 -80 -73 -69 -86 -91

© Alcatel 87




> Power control DL

• Thresholds:

L_RXLEV_DL_P = -85dBm POW_INC_FACTOR = 0.6

U_RXLEV_DL_P = -75dBm POW_RED_FACTOR = 0.8

L_RXQUAL_DL_P = 2.9 MAX_POW_INC = 16dB

U_RXQUAL_DL_P = 1 MAX_POW_RED = 16dB

A_QUAL_PC = 4 BS_P_CON_ACK = 3s

A_LEV_PC = 4 BS_TXPWR_MIN = -16dB

• Using the Trace Abis Excel file, find each parameter value:

POW_INC_STEP_SIZE = ? BS_P_CON_INT = ?

POW_RED_STEP_SIZE = ? OFFSET_RXQUAL_FH = 0 or 1 ?

• Which phenomenon can you observe as regards the successive PC commands?

© Alcatel 88



2.5 Handover Detection





Handover Detection


Handover Management

Exercise

© Alcatel 89



2.5 Handover DetectionHandover main objective

> Send connected MS to another cell

• When needed: “rescue/emergency” handover

• If useful: “better cell” handover

> Toward the “best” cell

• From a radio point of view

– Power budget

– Level

• From a traffic point of view

– Less loaded target

• From a dynamic point of view

– MS speed

– “History” of the call

• From an operator point of view

> Emergency intercell handovers:

• These handovers are triggered when the call conditions deteriorate significantly in order to rescue the call. The causes are: "too low quality" , "too low level", " too long MS-BS distance", “too short MS-BS distance”, "consecutive bad SACCH frames", "level dropping under high threshold".

> Better cell HO:

• These handovers are triggered to improve the overall system traffic capacity. This spans: interference reduction, signalingload reduction, traffic unbalance smoothing. The basic assumption for these handovers is that they should respect the cell planning decided by the operator.

• The causes are: "power budget" , "high level in neighbor lower layer cell for slow mobile", "high level in neighbor cell in the preferred band" and “traffic handover”.

© Alcatel 90



> The BSC is analyzing averaged measurement results

– active channel pre-processing (measurements averaging and book-keeping)

> To detect need/utility to handover

– Handover detection process

> To choose/rank target cells according to several criteria

– Candidate cell evaluation process

> To perform the handover

– Handover management process

2.5 Handover DetectionPrinciples

© Alcatel 91



2.5 Handover DetectionFunctional entities

BSCBTS


HO Detection


HO Preparation

HO CandidateCell Evaluation

HO Management

HO Protocol

MSC

Assignment of HO functions in the ALCATEL BSS

> The HO Preparation function can also be named "handover algorithms" as the algorithms described are the "heart" of this function.

• The ALCATEL handover preparation is derived from the basic algorithm found in Annex A of the GSM Technical Specification 05.08.

• The handover preparation is in charge of detecting a need for handover and proposing a list of target cells. Therefore it can be divided into two processes: handover detection and handover candidate cell evaluation.

> The handover detection process analyzes the radio measurements reported by the BTS and triggers the candidate cell evaluation process each time a handover cause (emergency or better cell type) is fulfilled.

> The handover candidate cell evaluation works out a list of possible candidate cells for the handover. This list is sorted according to the evaluation of each cell as well as the layer they belong to (in a hierarchical network) and the frequency band they use (in a multiband network).

> Once the handover preparation is completed, the handover decision and execution (handover management entity) is performed under the MSC or BSC control. The directed retry preparation is performed by the handover preparation function.

• Once the directed retry preparation is completed, the directed retry is performed either under the BSC control (internal directed retry) or under the MSC control (external directed retry).

> An example of implementation of these functions except for directed retry is given in the GSM Technical Specification 05.08.

> The handover preparation requires indirectly input parameters provided by the function in charge of the radio link measurements.

> Most of the input data required by the handover functions are provided by a function called: Active channel pre-processing.

> The figure above depicts in a general way:

• the interconnections between these functions,

• the implementation of these functions in the ALCATEL BSS.

© Alcatel 92



> Based on the contents of the measurement results

> The BSC is computing the need or utility to trigger a handover

> HO causes 25, split into 2 main categories:

• Emergency handover

– quality, level, distance, etc.

• Better cell handover

– power budget, traffic, etc.

> Some are specific to hierarchical and concentric architectures

2.5 Handover DetectionHandover causes detection

> The process is achieved in the BSC.

> Each time a set of pre-processed (averaged) measurements is available, this process checks whether a handover is needed. If the need for a handover is detected, the target cell evaluation process is triggered.

> In case of a handover alarm, the handover detection process gives to the cell evaluation process:

• the preferred target cell layer: lower, upper or none.

• the raw candidate cell list, which can be either all neighbors, or the subset which verify the handover causes (plus other specific cells in particular cases). With each cell is given one of the handover causes which have been verified.

• The cause of handover.

> Four main handover categories are provided, depending on the cause of handover and the context of application. The context of application for a handover is either "intercell" (the handover is performed between two different cells) or "intracell" (the handover is performed in the same cell).

> The detection of a need for handover is performed through handover causes which are going to be detailed.

> The cause of handover is based either on a situation of emergency (this cause is therefore called "emergency cause") or on the existence of better conditions. In this last case, the name of the cause depends on the context of application: for intercellhandovers, it is called "Better cell cause". For intracell handovers, it is called "Better zone cause", as it is applied only in the case of interzone handovers in concentric or multiband cells.

© Alcatel 93



2.5 Handover DetectionHandover causes

> HO causes for standard networks

Emergency HO

Cause 2

Cause 3

Cause 4

Cause 5

Cause 6

Cause 10

Cause 11

Cause 15

Cause 16

Cause 26

Too low quality on the uplink

Too low level on the uplink

Too low quality on the downlink

Too low level on the downlink

Too long distance between the

MS and the BTS

Too low level on the uplink in

the inner zone

Too low level on the downlink in

the inner zone

High interference on the uplink

(intracell HO)

Aigh interference on the downlink

(intracell HO)

AMR channel adaptation HO

(HR to FR)

Better conditions HO

Cause 12

Cause 13

Cause 20

Cause 23

Cause 24

Cause 27

Cause 28

Cause 29

Power budget evaluation

Outer zonelevel Uplink &

Downlink

Forced directed retry

Traffic

(Modified in B8)

General capture

(Modified in B8)

AMR channel adaptation

HO (FR to HR)

Fast traffic HO

TFO HO

30 Move from PS to CS zone

> HO causes for Extended Cells:

• Emergency causes

– cause 22: too short MS-BTS distance

> HO causes for hierarchical or multiband network:

• Emergency causes

– cause 7: consecutive bad SACCH frames received in a microcell

– cause 17: too low level on the uplink in a microcell compared to a high threshold

– cause 18: too low level on the downlink in a microcell compared to a high threshold

• Better causes

– cause 14: high level in neighbor lower layer cell for slow mobile

– cause 21: high level in neighbor cell in the preferred band

© Alcatel 94



> CAUSE 2: too low quality on the Uplink

AV_RXQUAL_UL_HO > L_RXQUAL_UL_H + OFFSET_RXQUAL_FH

and AV_RXLEV_UL_HO <= RXLEV_UL_IH

and MS_TXPWR = min (P, MS_TXPWR_MAX)

and EN_RXQUAL_UL= ENABLE

• Size of window for averaging quality: A_QUAL_HO

• Size of window for averaging level: A_LEV_HO

2.5 Handover DetectionHandover Cause 2: UL Quality

Quality

Level

> Quality and Level causes (2, 3, 4, 5, 15, 16)

> The aim of these causes is to keep the call going when the radio link is degrading otherwise the radio link failure might be detected and the call released. These causes wait generally for the power control process to increase the BTS and MS power to their maximum values, except for the causes specific to microcellular environment.

> Handover on "too low level" is used to avoid situations where the interference level is low, while the attenuation is quite high. These conditions may appear for example in big city streets which enable a line of sight propagation from the BTS antenna. Thereis in this case a risk of abrupt quality degradation, if the MS moves away from the line of sight street.

> In case of simultaneous low-level and low-quality signals, an intercell handover is requested.

© Alcatel 95



> CAUSE 3: too low level on the uplink

AV_RXQUAL_UL_HO <= L_RXQUAL_UL_H + OFFSET_RXQUAL_FH

and AV_RXLEV_UL_HO < L_RXLEV_UL_H

and MS_TXPWR = min (P, MS_TXPWR_MAX)

and EN_RXLEV_UL= ENABLE



2.5 Handover DetectionHandover Cause 3: UL Level

Quality

Level

© Alcatel 96



> CAUSE 4: too low quality on the downlink

AV_RXQUAL_DL_HO > L_RXQUAL_DL_H + OFFSET_RXQUAL_FH

and AV_RXLEV_DL_HO <= RXLEV_DL_IH

and BS_TXPWR = BS_TXPWR_MAX

and EN_RXQUAL_DL= ENABLE



2.5 Handover DetectionHandover Cause 4: DL Quality

Quality

Level

© Alcatel 97



2.5 Handover DetectionHandover Cause 5: DL Level

> CAUSE 5: too low level on the downlink

• AV_RXQUAL_DL_HO <= L_RXQUAL_DL_H + OFFSET_RXQUAL_FH

• AV_RXLEV_DL_HO < L_RXLEV_DL_H

• BS_TXPWR = BS_TXPWR_MAX

• and EN_RXLEV_DL= ENABLE



Quality

Level

© Alcatel 98



> CAUSE 6: Too long distance between the MS and the BTS

AV_RANGE_HO > U_TIME_ADVANCE

and EN_DIST_HO= ENABLE

• Size of window for distance averaging: A_RANGE_HO

2.5 Handover DetectionHandover Cause 6: Distance

Too long distanceBTS

> This cause is used when a dominant cell provides a lot of scattered coverages inside other cells, due to propagation conditions of the operational network. The consequence of these spurious coverages is the probable production of a high level of co-channel interference.

> This cause is different from the others as it is more preventive. It does not make use of the propagation conditions of a call. It just does not allow an MS to talk to a BTS if it is too far away.

> It may happen for example that some peculiar propagation conditions exist at one point in time that provide exceptional quality and level although the serving BTS is far and another is closer and should be the one the mobile should be connected to if the conditions were normal.

> It may then happen that these exceptional conditions suddenly drop and the link is lost, which would not have happened if the mobile had been connected to the closest cell. So for these reasons, this cause does not wait for the power control to react.

© Alcatel 99



> Emergency handovers specific to concentric cells

• Intracell handovers from inner to outer zone

• cause 10: too low level on the uplink in inner zone

• cause 11: too low level on the downlink in inner zone

> May be triggered

– From inner zone of a concentric cell

– Towards outer zone, same cell

2.5 Handover DetectionHandover algorithms for concentric cells

Conce

ntric cellIn

n e r z on

e

Outer zone

© Alcatel 100



> CAUSE 10: too low level on the uplink in the inner zone

AV_RXLEV_UL_HO < RXLEV_UL_ZONE

and MS_TXPWR = min (P, MS_TXPWR_MAX_INNER)

• Averaging window: A_LEV_HO

2.5 Handover DetectionHandover algorithms for concentric cells: cause 10

© Alcatel 101



> CAUSE 11: too low level on the downlink in the inner zone

AV_RXLEV_DL_HO < RXLEV_DL_ZONE

and BS_TXPWR = BS_TXPWR_MAX_INNER

• Averaging window: A_LEV_HO

2.5 Handover DetectionHandover algorithms for concentric cells: cause 11

© Alcatel 102



> CAUSE 13: too high level on UL and DL in the outer zone

• Better condition intracell handover

• If the cell is a multi-band cell, cause 13 is checked only for multi-band MSs

> May be triggered

– From outer zone of a concentric cell

– Towards inner zone, same cell

2.5 Handover DetectionHandover algorithms for concentric cells: cause 13 (1/6)

Conce

ntric cell

Inn e r z o

n

e

Outer zone

© Alcatel 103



> CAUSE 13: too high level on UL and DL in the outer zone

AV_RXLEV_UL_HO > RXLEV_UL_ZONE +

+ ZONE_HO_HYST_UL +

+ (MS_TXPWR - MS_TXPWR_MAX_INNER) +

+ PING_PONG_MARGIN(0,call_ref)

and AV_RXLEV_DL_HO > RXLEV_DL_ZONE ++ ZONE_HO_HYST_DL ++ (BS_TXPWR - BS_TXPWR_MAX_INNER) ++ PING_PONG_MARGIN(0,call_ref)

and AV_RXLEV_NCELL_BIS(n) <= neighbour_RXLEV(0,n)

and EN_CAUSE_13 = ENABLE (B7)

and EN_BETTER_ZONE_HO = ENABLE

• Averaging windows: A_LEV_HO and A_PBGT_HO (for n)


© Alcatel 104



> ZONE_HO_HYST_UL

• UL static hysteresis for interzone HO from outer to inner

– In case of multi-band cell, should take into account the difference of propagation between GSM and DCS

• Added to cause 10 threshold RXLEV_UL_ZONE

> ZONE_HO_HYST_DL

• DL static hysteresis for interzone HO from outer to inner

– In case of multi-band cell, should take into account the difference of propagation between GSM and DCS and the difference of BTS transmission power in the two bands

• Added to cause 11 threshold RXLEV_DL_ZONE


© Alcatel 105



> PING_PONG_MARGIN(0,call_ref)

• Penalty PING_PONG_HCP put on cause 13 if

– The immediately preceding zone in which the call has been is the inner zone of the serving cell

– And The last handover was not external intracell

– And T_HCP is still running

• PING_PONG_MARGIN(0,call_ref) = 0

– If the call was not previouslyin serving’s inner zone

– Or T_HCP has expired


Conce

ntric cell

Inn e r z o

n

e

Outer zone

© Alcatel 106



> neighbour_RXLEV(0,n)

• Concentric cells are designed to create an INNER zone

– protected from external interferers

– and creating no interferences on other cells

– … to be able to face more aggressive frequency reuse in INNER zone TRXs

• neighbour_RXLEV(0,n) tuning enables to avoid handovers if the MS position will lead to interferences

• the condition is checked towards all neighbor cells belonging to the same layer and band than the serving cell


Concentric cellOuter zone

?

Inner zoneinterferer 1

Inner zoneinterferer 2Inner zone

© Alcatel 107



> EN_CAUSE_13

• Load balance between inner and outer zones may be allowed by setting EN_LOAD_BALANCE = ENABLE

• If EN_LOAD_BALANCE = ENABLE

– If INNER zone is less loaded than OUTER,EN_CAUSE_13 = ENABLE

– If INNER zone is more loaded than OUTER,EN_CAUSE_13 = DISABLE

• If EN_LOAD_BALANCE = DISABLE

– EN_CAUSE_13 = ENABLE


© Alcatel 108



> Outgoing intercell handovers from concentric cells

• As explained here before, the MS located in a concentric cell can make intercell, emergency orbetter condition HO regardless their current zone

– For example, an MS locatedin the INNER zone of aconcentric cell can makedirectly a HO cause 12towards another cell,WITHOUT having totrigger any cause 10 or 11to the OUTER zone before.

2.5 Handover DetectionOutgoing intercell handovers from concentric Cell


Inner zone


Inner zone


Inner zone

> The only restrictions are linked to EN_MULTI-BAND_PBGT_HO and EN_BI-BAND_MS parameters.

© Alcatel 109



> Incoming intercell handovers towards a concentric cell

• In case an MS is making an incoming handover towards a concentric cell (due to outer PBGT measurements,etc.), a TCH may be allocated

– either in the INNER or in the OUTER zone, as for call setup

– depending on radio conditions

• In case of a multi-band cell, if the MS is not multi-band, it will always be sent to the OUTER zone

2.5 Handover DetectionIncoming intercell handovers towards Concentric Cell (1/2)


Inner zone

Cell

??

© Alcatel 110



> Use part of Handover cause 13 algorithm on each potential target

> IF Cell(n) is external

– The MS is directed to the OUTER zone of (n)

> ELSE (cell(n) is internal)

• IF

AV_RXLEV_NCELL(n) > RXLEV_DL_ZONE + ZONE_HO_HYST_DL ++ (BS_TXPWR - BS_TXPWR_MAX_INNER)

and EN_BETTER_ZONE_HO = ENABLE

– The MS is directed towards the INNER zone

• ELSE

– The MS is directed towards the OUTER zone

2.5 Handover DetectionIncoming intercell handovers towards Concentric Cell (2/2)

© Alcatel 111



> CAUSE 12: Power budget

• Decision based mainly on comparison of serving and neighborcells for:

– downlink level of serving and neighbor cells

– maximum emitting level of MS

• Aiming at decreasing UL & DL emitted power

• Should be the “normal” handover type

– no matter of emergency

2.5 Handover DetectionHandover Cause 12: Power Budget (1/11)

> In this case, there is another cell with a better power budget i.e., the link quality can be improved or maintained with a reduced transmit power of both the MS and the BTS. The radio link is not degraded but there is the opportunity to decrease the overall interference level by changing the serving cell of the given MS.

> In conjunction with power control, it presents the advantage to keep the interference as low as possible, since it minimizes thepath loss between the BTS and the MS.

> This cause is especially designed to cope with the requirement that the mobile should be connected with the cell with which the lowest possible output powers are used. To assess which of the cells is this "best cell", the algorithm performs every measurement reporting period the comparison of the path loss in the current and in the neighbor cell. This is a feature special to GSM which is made possible because the mobile measures the adjacent cell signal levels and reports the six best ones.

> This power budget gives the difference in path loss between the current cell and the adjacent cells reported by the mobile.

> When PBGT(n) is greater than 0, then the path loss from cell n is less than the path loss from the serving cell and thus the radiated power in the downlink direction, and therefore in the uplink direction as well, will be lower in cell n than in the current cell.

> However it would not be advisable to hand over the MS to another cell as soon as PBGT is greater than 0, because the MS would probably oscillate between the two adjacent cells as the propagation conditions vary. An hysteresis mechanism is implemented to avoid this undesirable effect.

> No PBGT between different layers.

> Ok between different bands if EN_INTERBAND_PBGT_HO = 1

© Alcatel 112



> CAUSE 12: Power budget equation

PBGT(n) = AV_RXLEV_NCELL(n) - AV_RXLEV_PBGT_HO

- (BS_TXPWR_MAX – AV_BS_TXPWR_HO)

- (MS_TXPWR_MAX(n) – MS_TXPWR_MAX)

- PING_PONG_MARGIN(n, call_ref)


> The MS may be handed over from the serving cell indexed 0 to a neighbor cell indexed n only if the power budget exceeds the handover Margin(0,n). The handover Margin(0,n) can be modified according to the traffic situation in the serving cell and the neighbor cell n. In this way, power budget handover can be delayed towards a loaded cell and traffic load handover can be triggered from a loaded cell. Once the MS is handed over, the same algorithm is applied in the new cell, and a new PBGT is computed (which will be close to the opposite value of PBGT in the old cell) and compared to a new HOMargin. (Thus, the global hysteresis (from cell 0 to cell n and back to cell 0) is the sum of the two HOMargins).

> However, It is still possible that a ping-pong mechanism is created by different handover causes, for instance a handover may be triggered towards a neighbor cell for bad quality, but in the neighbor cell, a handover back may be triggered for power budget reasons. In order to avoid this, an additional anti-ping-pong mechanism is implemented in the power budget calculation. It enables to penalize for a certain time the cell on which the call has been before.

> In case of handover from SDCCH to SDCCH, this cause does not take the traffic situation into account.

> In multiband cell environment, the mobile can operate in a different band than the frequency band of the BCCHs. This can lead to circular ping-pong handovers from the inner zone if the new band is DCS 1800 or to the impossibility to trigger PBGT handovers from the inner zone if the preferred band is GSM 900.

> To avoid this problem, when the MS is in the inner zone of a multiband cell, it may be handed over from the serving cell indexed 0 to a neighbor multiband cell indexed n only if the power budget exceeds the handover Margin(0,n) plus the offset handover margin which allows to handicap or favor the PBGT (In the inner zone, the cause “power budget” is only checked between multiband cells, in a way to maintain the MS in the preferred band).

> The offset handover margin can possibly be used in concentric cells.

© Alcatel 113




• AV_RXLEV_NCELL

– received level of BCCH of neighbor cell

• AV_RXLEV_PBGT_HO

– received level of serving cell (BCCH or not)

• AV_RXLEV_NCELL - AV_RXLEV_PBGT_HO

– the highest is the best neighbor cell

– but serving might not be at the maximum level (with DL power control)

– necessity to have a corrective factor






> ∆∆∆∆ BCCH = AV_RXLEV_NCELL(n) - (AV_RXLEV_PBGT_HO + C)

• with C = BS_TXPWR_MAX - AV_BS_TXPWR_HO.

> This corresponds to the difference of received BCCH signal levels.

• A correction factor C is taken into account for the serving cell, because the received signal level (i.e. AV_RXLEV_PBGT_HO) may not be measured on BCCH.

© Alcatel 114




• BS_TXPWR_MAX – AV_BS_TXPWR_HO

– BS_TXPWR_MAX are attenuations, not absolute level

– = (“bts_max_power”+BS_TXPWR_MAX) -(“bts_max_power”+AV_BS_TXPWR_HO)

– AV_BS_TXPWR_HO: average of BS_POWER over A_PBGT_HO measurements

– corrective factor used to compensate for the fact that the serving cell may not emit at the maximum level

• AV_RXLEV_NCELL-[AV_RXLEV_PBGT_HO+(BS_TXPWR_MAX-AV_BS_TXPWR_HO)]

– compare received level of neighbor and serving cells as if the serving one was emitting at the maximum level






© Alcatel 115





• MS_TXPWR_MAX(n)

– maximum emitting power for the MS in neighbor cell n

• MS_TXPWR_MAX

– maximum emitting power for the MS in the serving cell

> MS_TXPWR_MAX(n) - MS_TXPWR_MAX

• Corrective factor to compensate for the difference of maximum power of each cell

• MS_TXPWR_MAX(n) - MS_TXPWR_MAX = bts_max_power(n) -bts_max_power

– which should be the case if delta_path_loss is equilibrated

– if not exact, can be corrected with HO_MARGIN(0,n)





> Then, another correction factor must be taken into account because the maximum BS powers of the serving and neighbor cells may be different:

∆∆∆∆ TXPWR= MS_TXPWR_MAX(n) - MS_TXPWR_MAX.

> As the first step of calculation is based on the downlink parameters, this correction factor should be based on the maximum BS powers used in the serving and neighbor cells.

> Two reasons (which are not completely de-correlated) for not using the BS powers can be envisaged:

• for a given cell, the GSM does not specify formally the maximum BS power of the neighbor cells. Only BS_TXPWR_MAX is defined (it is sent on the air interface),

• it is not easy for the evaluating BSC to know the maximum BS powers of the neighbor cells.

> The use of the maximum MS powers requires that the difference of MS powers is equal to the difference of BS powers. This condition is met in most cases. If it is not the case, the difference can be corrected by the operator with the HO_MARGIN(0,n) parameter (HO hysteresis).

> PBGT >0: the neighbor cell is more advantageous as the path loss is lower than in the current cell.

> PBGT <0: the serving cell is more advantageous than the current cell.

© Alcatel 116




• Hysteresis to avoid ping-pong HO

• Static hysteresis defined for each couple of cells:HO_MARGIN (0,n)

– can also be used to correct delta_path_loss

• “Dynamic” penalty for call coming from cell n: ping_pong_margin(n,call_ref)

– penalty applied during a limited duration: T_HCP

– not used if call arrived with a forced directed retry

– penalty defined on a cell basis






> The main drawback of this handover category is the risk of "ping-pong " effect, which is an oscillating back and forth handover between two (or three) cells. As the "better cell" handovers are meant to find the "best cell", the variation of the radio conditions will trigger a big amount of better cell handovers, if the algorithms have a too sensitive reaction. Hence, some mechanisms are forecast, in order to prevent these oscillations from occurring repeatedly at given places.

> PING_PONG_MARGIN(n,call_ref) is a penalty put on the cell n if:

• it is the immediately precedent cell on which the call has been,

• this cell belongs to the same BSC as the serving cell,

• the call has not performed a forced directed retry towards the serving cell,

• less than T_HCP seconds have elapsed since the last handover.

– In this case PING_PONG_MARGIN(n,call_ref) = PING_PONG_HCP

> If the call was not precedently on cell n, or if the preceding cell was external, or if the call has just performed a forced directed retry, or if the timer T_HCP has expired,

– then PING_PONG_MARGIN(n,call_ref) = 0

© Alcatel 117




• ping_pong_margin example


Cell Cell Cell

Case 1

Case 3

Case 2

OK1

Ping-pong in normal case OK with ping_pong_margin

Not a ping-pong case OK with ping_pong_margin and T_HCP

2

3

> This chart shows the efficiency of the anti-ping_pong mechanism.

> But, never forget that anti-ping-pong mechanism distorts the serving areas of the cells.

> This is why interference problems might occur when enabling this mechanism. Tuning PING_PONG_HCP parameter is thus very important.

> Warning: this mechanism is not applied for emergency handovers (new mechanism in B7 exists for capture HO, based on T_INHIBIT_CPT timer).

© Alcatel 118





> If EN_TRAFFIC_HO(0,n)=ENABLE

> Then PBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGIN_INNER

+ max(0, DELTA_HO_MARGIN(0,n))(n=1…BTSnum)

> Else PBGT(n) > HO _MARGIN(0,n)+OFFSET_HO_MARGIN_INNER

> AND AV_RXLEV_PBGT_HO ≤ RXLEV_LIMIT_PBGT_HO

> AND EN_PBGT_HO = ENABLE

> Size of window for level averaging: A_PBGT_HO

> Cause 12 HO is correlated with HO cause 23. This is why there are two equations according to the activation of HO cause 23 (EN_TRAFFIC_HO).

© Alcatel 119





> Mechanism to avoid PBGT HO if the level from the serving cell ishigh enough

> RXLEV_LIMIT_PBGT_HO: threshold above which it is not necessary to trigger a handover on power budget

> AV_RXLEV_PBGT_HO: average of the received levels over A_PBGT_HO measurements

> Specific to particular algorithms (not mentioned in this course)

> OFFSET_HO_MARGIN_INNER: offset which allows to take into account the radio differences between outer and inner zones (especially in case of multi-band cells)

> RXLEV_LIMIT_PBGT_HO: Dense Network Handover Regulator features

> The feature aims at optimizing the better cell handovers, especially in the microcellular environment.

> In very dense networks, there is a lot of overlapping between adjacent cells: a better cell handover will be realized very often. Since B6, the Alcatel BSS tunes the number of handovers performed to the accurate need by taking into account the level received by the serving cell.

> Therefore, the best trade-off between quality of speech and intempestive handovers is achieved.

> Why?

• Especially in microcellular environment (where cell radius is smaller), the better cell HO (based on Power Budget) is likely to be performed at a high rate to the detriment of the quality.

• But it is necessary to maintain the better cell HO.

> How?

• With a modification of the power budget triggering cause.

> Principles:

• HO cause 12 (Power Budget HO) is modified and takes into account the received downlink level of the serving cell (new criterion): if the received level is high enough, there is no need to perform an HO.

> Consequence:

• Less HOs when the number of overlapping cells is high.

W/O B6W/O B6W/O B6W/O B6 WITH B6WITH B6WITH B6WITH B6

© Alcatel 120





> Specific to traffic considerations

> DELTA_HO_MARGIN(0,n): evaluated according to the traffic situation of the serving cell and the neighbor cell n (Traffic_load(n)) in the following way:

> If Traffic_load(0) = high and Traffic_load(n) = low, – DELTA_HO_MARGIN(0,n) = - DELTA_DEC_HO_margin

> If Traffic_load(0) = low and Traffic_load(n) = high,– DELTA_HO_MARGIN(0,n) = DELTA_INC_HO_margin

> Else – DELTA_HO_MARGIN(0,n) = 0

> Philosophy

> This mechanism aims at penalizing cause 12 detection when the traffic in the serving cell is low and is high in the cell n.

> DELTA_HO_MARGIN(0,n) is evaluated according to the traffic situation of the serving cell and the neighbor cell n (Traffic_load(n)) in the following way:

• If Traffic_load(0)=high and Traffic_load(n)=low

– DELTA_HO_MARGIN(0,n)= -DELTA_DEC_HO_margin

• If Traffic_load(0)=low and Traffic_load(n)=high

– DELTA_HO_MARGIN(0,n)= DELTA_INC_HO_margin

• else DELTA_HO_MARGIN(0,n)=0

where DELTA_DEC_HO_margin allows the cause 23 (traffic handover) detection.

> When the traffic in the serving cell is high and is low in the cell n:

• DELTA_INC_HO_margin allows to penalize the cause 12 detection when the traffic in the serving cell is low and is high in the cell n.

Note:In the case of concentric or multiband cells, if the channel is in the inner zone (ZONE_TYPE = INNER), BS_TXPWR_MAX and MS_TXPWR_MAX in equation must be replaced by BS_TXPWR_MAX_INNER and MS_TXPWR_MAX_INNER respectively.

If the channel is in the outer zone (ZONE_TYPE = OUTER), the formulation of equation is not changed.

Note: The value of PBGT(n) is calculated every SACCH period for each neighbor cell n whose measures are kept in the book-keeping list.

© Alcatel 121





> Traffic_load() is a function managed for every cell of a BSC

> Traffic_load() can have three values:

• high: cell is loaded

• low: cell is unloaded

• indefinite: cell is neither loaded nor unloaded

> Traffic_load() value is modified according to the long term traffic evaluation algorithm using the following parameters:

• A_TRAFFIC_LOAD, N_TRAFFIC_LOAD, HIGH_TRAFFIC_LOAD, IND_TRAFFIC_LOAD, LOW_TRAFFIC_LOAD: can be modified per cell

• TCH_INFO_PERIOD: cannot be modifiedAnnex 3

> TCH_INFO_PERIOD = 5s period used by the BSC to count the number of free TCHs.

© Alcatel 122



2.5 Handover DetectionHandover Cause 23: Traffic (1/2)

> CAUSE 23: Traffic Handover

> DELTA_HO_MARGIN(0,n) < 0dB

> AND PBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGNIN_INNER+ DELTA_HO_MARGI (0,n)

(n=1…BTSnum)

> AND EN_TRAFFIC_HO(0,n) = ENABLE

> Size of window for level averaging: A_PBGT_HO

> The principle of this handover is to reduce the size of the serving cell when it is high-loaded relatively to a low-loaded cell.

> When the mobile moves away from the BTS, the power budget will increase and a better cell handover will be triggered earlier.

> It is recommended to inhibit Traffic handover towards 1-TRX cells. These cells do not have enough resources to receive incoming handovers due to congestion of neighbor cells. Moreover because of the great variation of traffic in the 1-TRX cells, traffic load is never considered as low.

> This cause is inhibited for handover from SDCCH to SDCCH.

> Cause 23 is checked over all the neighboring cells belonging to the same layer. It means that it is checked between cells whose CELL_LAYER_TYPE is single or upper, between cells whose CELL_LAYER_TYPE is lower, and between cells whose CELL_LAYER_TYPE is indoor.

> In addition to the condition on the cell layer type, the cell frequency band condition for checking Cause 23 is as follows whether or not the MS is in the inner zone of a multi-band cell:

• a) The MS is not in the inner zone of a multi-band cell

– If the flag EN_MULTI-BAND_PBGT_HO is set to “disabled”, Cause 23 must not be checked between cells which use different frequency bands (i.e cells having different CELL_BAND_TYPE).

– If the flag EN_MULTI-BAND_PBGT_HO is set to “enabled”, Cause 23 will be checked over all the neighboringcells without any cell frequency band restriction.

• b) The MS is in the inner zone of a multi-band cell

– If the flag EN_MULTI-BAND_PBGT_HO is set to “disabled”, Cause 23 is checked over all the neighboring cell multi-band cells (FREQUENCY_RANGE= PGSM-DCS1800 or EGSM-DCS1800) which belong to the same BSC as the serving cell.

– If the flag EN_MULTI-BAND_PBGT_HO is set to “enabled”, Cause 23 will be checked over all the neighboringcells without any cell frequency band restriction.

© Alcatel 123



2.5 Handover DetectionHandover Cause 23: Traffic (2/2)

> CAUSE 23: Traffic Handover

• DELTA_HO_MARGIN(0,n) computation is already described in

Cause 12 HO

• DELTA_HO_MARGIN(0,n) < 0dB means that

– The serving cell is loaded

– The target cell is unloaded

• PBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGIN_INNER

+ DELTA_HO_MARGIN(0,n) (n=1…BTSnum)

– This constraint is less discriminative than Cause 12

– In specific traffic distribution, this cause is triggered before

cause 12

© Alcatel 124



2.5 Handover DetectionHandover Cause 12 & 23 interworking

> Cause 12 & 23: A dynamic way to handle traffic load

PBGT (n2)

PBGT (n1)

Traffic_loadTraffic_load(n2)=high

Traffic_load(n1)=low

Other cases Traffic_load(n2)=low

Traffic_load(n1)=high

HO_MARGING(n1, n2) + DELTA_INC_HO_margin

HO_MARGING(n1, n2)

HO_MARGING(n1, n2) - DELTA_DEC_HO_margin

HO_MARGING(n2, n1) - DELTA_DEC_HO_margin

HO_MARGING(n2, n1)

HO_MARGING(n2, n1) + DELTA_INC_HO_margin

PBGT Handover

PBGT Handover

2 x HO_MARGIN+ DELTA_INC_HO_margin- DELTA_DEC_HO_margin

2 x HO_MARGIN

PBGT Handover

Traffic Handover

PBGT Handover

Traffic Handover

Handover from n1 to n2

Handover from n2 to n1

N2 loaded

N1 loaded

> The figure represents the triggering areas of PBGT and traffic handovers according to the traffic load in the serving cell and in the neighbor cell.

© Alcatel 125



> Directed Retry is:

• an SDCCH to TCH intercell handover

• Triggered during call setup procedure

> If the serving cell is completely congested, the MS is allocated an SDCCH

> If no TCH is available, the MS is queued

• Under certain conditions, the MS obtains TCH in another cell

> SDCCH-TCH handover on:

• better condition or emergency causes = Directed Retry

• cause 20 = Forced Directed Retry

> Internal and External Directed Retries are possible (since B6.2)

2.5 Handover Detection Directed Retry principles

© Alcatel 126



> Directed Retry

• Set on a per cell basis with parameter EN_DR

• Same behavior as TCH HO

• Intercell handover causes are checked (i.e. all HO causes except 10, 11 and 13 (concentric cells) and causes 15 and 16 (intracellHO))

• candidate cell evaluation process: same as for TCH HO

2.5 Handover Detection Directed Retry

© Alcatel 127



> CAUSE 20: Forced Directed Retry

AV_RXLEV_NCELL_DR(n) > L_RXLEV_NCELL_DR(n)

And EN_FORCED_DR = ENABLE

• EN_FORCED_DR value is only relevant if EN_DR = true

• AV_RXLEV_NCELL_DR(n) is calculated with A_PBGT_DR window

• if less than A_PBGT_DR samples are available, the average value is calculated with the available samples and the averagingwindow is filled in with -110 dBm

2.5 Handover Detection Forced Directed Retry: cause 20

© Alcatel 128



> Pre-ranking

• using PREF_LAYER, PRIORITY(0,n), frequency band

> Filtering process

• AV_RXLEV_NCELL_DR(n) > RXLEVmin(n)+max(0,MS_TXPWR_MAX(n) - P)

• Number of free TCHs t(n) > FREElevel_DR(n)

> Remaining cells are sorted according their PBGT_DR(n) (averaging window A_PBGT_DR)

• PBGT_DR(n) = AV_RXLEV_NCELL_DR(n) - AV_RXLEV_PBGT_DR - (BS_TXPWR_MAX - BS_TXPWR) - (MS_TXPWR_MAX(n) - MS_TXPWR_MAX)

2.5 Handover Detection FDR: Candidate cell evaluation

© Alcatel 129



> L_RXLEV_NCELL_DR(n): level required in the neighbor cell n

– The parameter considered is the one set in the neighbor cell

– The default value depends on network architecture

– See next slide

> Freelevel_DR(n): number of free TCH channels required in the neighbor cell n

– The parameter considered is the one set in the neighbor cell

– Default value = 0 to 4 TCHs (linked to the nb of TRXs)

> A_PBGT_DR: Averaging window

– Default value = 4 SACCHs

2.5 Handover Detection FDR: parameters

© Alcatel 130



2.5 Handover DetectionCause 24: general capture

Serving cell

Cell

Cell

Cell

Cell

> CAUSE 24: general capture

• Capture handover

– Modified in B8:Inhibition of capture handovers for “Single layer serving cell”

• May be triggered

– From all cells

– Towards all cells except serving

– Can be used to capture traffic by any cell, whatever its type, band, etc.

© Alcatel 131



> CAUSE 24: general capture

AV_RXLEV_NCELL(n) > L_RXLEV_CPT_HO(0,n) + max (0, [MS_TXPWR_MAX(n) - P])

and Traffic_load(0) = CAPTURE_TRAFFIC_CONDITION

and Traffic_load(n) ≠≠≠≠ HIGH

and EN_GENERAL_CAPTURE_HO = ENABLE

• Size of window for averaging level: A_PBGT_HO

• CAPTURE_TRAFFIC_CONDITION can take 3 values: ANY_LOAD (default), HIGH, NOT_LOW

• Anti ping-pong: not checked if T_INHIBIT_CPT is running – new in B8 for single layer

2.5 Handover DetectionCause 24: general capture

> Case the serving cell is in the upper or single layer (CELL_LAYER_TYPE(n0) = upper or single):

> Condition 1: The immediately preceding cell n-1is in the indoor or lower layer, i.e. CELL_LAYER_TYPE(n

–1) = lower or

indoor, or the frequency band of the immediately preceding cell n-1is different from the frequency band of the serving cell n

0,

i.e. CELL_BAND_TYPE(n–1) <> CELL_BAND_TYPE(n

0).

> Condition 2: The call has previously performed i) an emergency internal handover on quality (Cause 2, 4, and 7) towards the serving cell or ii) an external handover with the A interface GSM cause “uplink quality or downlink quality” and there is a bi-directional adjacency link between the preceding external cell n

-1and the serving cell n

0.

– If Conditions 1 and 2 are fulfilled the timer T_INHIBIT_CPT is started

© Alcatel 132



2.5 Handover DetectionHandover Cause 28: Fast Traffic HO (1/4)> CAUSE 28: Fast Traffic HO

• Push out of a cell a mobile in dedicated mode to allow a queued request to be served in the serving cell

– Complement the current traffic HO (Cause 23), for sudden traffic peaks (no averaging window used)

– More efficient where the overlap of adjacent cells is reducedMost appropriate MSto be pushed out

New c

all attempt

CongestedServing cell

Neighbor cell Cell

Neighbor cell Cell

Upper layer cell

HO

HOMost appropriate MSto be pushed out

New c

all attempt

Congested

Serving cell

• AV_RXLEV_NCELL( n) > L_RXLEV_NCELL_DR( n) + max(0,[MS_TXPWR_MAX( n)-P])

– The threshold L_RXLEV_NCELL_DR(n) is the observed level from the neighbor cell n at the border of the area where fast traffic handovers are enabled. This threshold fixes the size of the overlapping area where fast traffic handovers can be performed. It should be greater than RXLEVmin(n).

• And t(n) > FREElevel_DR(n)

– FREElevel_DR(n) is the minimum threshold of free TCHs in the neighbor cell n for forced directed retry and fast traffic handover.

– t(n) is the absolute number of free (dual rate) TCHs in the neighbor cell n.

– For external cells, t( n) is fixed to the arbitrary value t(n) = 255. Therefore, setting FREElevel_DR(n) to 255 for an external cell inhibits outgoing external fast traffic handover towards this cell. Setting FREElevel_DR(n) to any other value will allow outgoing external fast traffic handover towards this cell.

• EN_CAUSE_28 = enable

– The flag EN_CAUSE_28 is not an OMC flag but a HOP flag.

© Alcatel 133



2.5 Handover DetectionHandover Cause 28: Fast Traffic HO (2/4)> CAUSE 28: Fast Traffic Handover

• Cause 28 is only checked if the channel of the candidate MS can support the channel rate (HR or FR) required by the queued request:

• HO is triggered when a request is queued at the top of the queue

Queued Request Candidate MS

HR

HR

HR orFR on dual rate TRX

FR (whatever the TRX type)

© Alcatel 134



2.5 Handover DetectionHandover Cause 28: Fast Traffic HO (3/4)

> CAUSE 28: Fast Traffic Handover equation

AV_RXLEV_NCELL(n) > L_RXLEV_NCELL_DR(n) + max(0,[MS_TXPWR_MAX(n)-P])

AND t(n) > FREElevel_DR(n)

AND EN_CAUSE_28 = ENABLE

AND EN_FAST_TRAFFIC_HO = ENABLE

� Size of window for averaging level: A_PBGT_DR

� Same thresholds and window as Cause 20 (Forced Directed Retry)

� EN_CAUSE_28 is an internal HOP process variable

© Alcatel 135



2.5 Handover DetectionHandover Cause 28: Fast Traffic HO (4/4)

> CAUSE 28: Fast Traffic Handover process

DHCPEND

- Cause number 28- Reference of the call to handover(which corresponds to the firstcandidate MS received)

Start HO

Assignment request queued - Queued request reference- Channel rate of queued request

Fast Traffic HO Request

Yes

EN_CAUSE_28=enable

EN_CAUSE_28=disable

HO alarm:cause 28?

NOK

DHCPEND

Requeststill queued?

Resource AllocationManagement

HandoverPreparation

T_FILTERis started

HandoverManagement

OK

Check first2 conditions of cause 28

- Queued request reference- Reference of MS can perform HO

Fast Traffic HO Acknowledge

Yes

No

NO

> HO cause 28 process:

• If EN_FAST_TRAFFIC_HO = enable, when an assignment request (or external emergency HO request) is queued, the RAM process sends to the HOP process a Fast Traffic HO request which contains the queued request reference and its channel rate.

• Then, HO cause 28 becomes checkable (EN_CAUSE_28=enable).

• Once an HO alarm for cause 28 is triggered, the flag EN_CAUSE_28 is set to “disable” so as not to perform more than one handover. In the same time, the HOP process gets back to the RAM process a Fast Traffic HO Acknowledge which contains the queued request reference and the reference of the MS that can perform HO.

• If several answers are sent to the RAM process, only the first one corresponding to the queued request is taken into account.

– The RAM process checks if the request is still queued. If that is so, the RAM process asks the HOP process to start HO for this mobile; otherwise the process is stopped.

• Once the HOP process receives this message, the first two conditions of Cause 28 (good enough level, enough free resources in the target cell) are checked one more time. If the conditions are fulfilled, the HOP process sends an alarm to the HOM entity and the timer T_FILTER is started ; otherwise the process is stopped.

Note: the first two conditions of cause 28 are tested twice in order to be sure that the candidate cells are still valid when the « cause 28 start HO » message is received from the RAM process.

© Alcatel 136



> CAUSE 15: High interference on the uplink

• Intracell HO

AV_RXQUAL_UL_HO > THR_RXQUAL_CAUSE_15 +OFFSET_RXQUAL_FH

AND AV_RXLEV_UL_HO > RXLEV_UL_IH


AND [ no previous intracell handover for this connection failed

OR EN_INTRACELL_REPEATED = ENABLE ]



2.5 Handover DetectionHandover Cause 15: UL Interference

> THR_RXQUAL_CAUSE_15 and EN_CAUSE_15 are not parameters but variables defined just after.

> In B7:

• New causes (26 & 27) introduced due to AMR support

– Cause 26 is an emergency condition:

– Intracell HO: speech codec from AMR-HR to AMR-FR

– Cause 27 is a better condition

– Intracell HO: speech codec from AMR-FR to AMR-HR

• Causes 15 & 16 are modified due to AMR support

– Specifics enablers and thresholds for AMR calls

– AMR emergency HO (cause 26) is triggered if cause 15 or 16 has already been triggered

• Cause 29 is created for intracell handover due to TFO

– Codec sharing and optimization for MTM calls

© Alcatel 137



> CAUSE 16: High interference on the downlink

• Intracell HO

AV_RXQUAL_DL_HO > THR_RXQUAL_CAUSE_16 + OFFSET_RXQUAL_FH

AND AV_RXLEV_DL_HO > RXLEV_DL_IH


AND [ no previous intracell handover for this connection failed

OR EN_INTRACELL_REPEATED = ENABLE ]



2.5 Handover DetectionHandover Cause 15: DL Interference

> THR_RXQUAL_CAUSE_16 and EN_CAUSE_16 are not parameters but variables defined after.

© Alcatel 138



2.5 Handover DetectionNew parameters for causes 15 & 16

> CAUSE 15 and CAUSE 16:

• THR_RXQUAL_CAUSE_15 (or 16) and EN_CAUSE_15 (or 16) are specific to HOP

• THR_RXQUAL_CAUSE_15 (or 16) =

– L_RXQUAL_XX_H for a non AMR call (same threshold as CAUSE 2 or CAUSE 4)

– L_RXQUAL_XX_H_AMR for an AMR call

• EN_ CAUSE _15 (or 16) =

– EN_INTRA_XX for a non AMR call

– EN_INTRA_XX_AMR for an AMR call

> XX = UL or DL

> For a non AMR call, the thresholds used are identical to the ones used for CAUSE 2 and CAUSE 4.

> In this case and if EN_INTRACELL_REPEATED = DISABLE, when aN HO CAUSE 15 (or 16) fails, it can be modified as UPLINK (or DOWLINK) QUALITY, HO CAUSE 2 (respectively HO CAUSE 4).

© Alcatel 139



2.5 Handover DetectionAdaptive Multi-rate codec (AMR)

> Principles:

• Two consecutive encodings: speech coding and channel coding

• With current codecs, the share of each coding is FIXED (not optimized)

Speech protection"against degradation"

22.8 Kbit/s (FR TS)

Speech protection"against degradation"

11.4 Kbit/s (HR TS)

Channel coding

Channel coding

FIXEDFIXEDFIXED

Radio

Radio

Speech coding

Speech information "useful part"

13 Kbit/sou 12.2 Kbit/s

(FR)(EFR)

Speech information "useful part"

5.6 Kbit/s (HR)

Speech coding

Voice

Voice

> Speech coding contains speech information (the “useful” part).

> Channel coding protects speech information (against radio degradations).

> The main speech codec currently used in GSM networks, speech Full Rate, is quite old. It has been specified more than 10 years ago. Around 1992, to increase network capacity, GSM has specified a half rate speech codec. But this codec showed strong limitations in terms of speech quality, especially for mobile to mobile calls (double transcoding degrades very much the speech quality of the half rate codec) and under poor radio conditions.

> Recently, studies on AMR have been launched to provide a solution to:

• Increase speech quality in full rate and half rate,

• Increase network capacity by offering a good half rate solution,

• Use a long-term solution, to avoid adding more and more codecs handled independently from the others.

© Alcatel 140



2.5 Handover DetectionAMR: codec and channel adaptation

• AMR uses a variable balance between speech coding and channel coding (CODEC Mode Adaptation)

• Choice between FR and HR Codecs: Channel Mode Adaptation

Variable channelcoding rate

22.8 Kbit/s (FR TS)

Variable channelcoding rate

Channel coding

Channel coding

Radio

Speech coding

Variable speech coding rate


Speech coding

Voice

Voice

FLEXIBLE

FLEXIBLEFLEXIBLE

4.75 Kbit/s5.15 Kbit/s5.9 Kbit/s


10.2 Kbit/s12.2 Kbit/s




11.4 Kbit/s (HR TS)(AMR HR 7.95 not supported)

Radio

> In order to adapt the intermediate rate, a set of speech codecs has been defined by ETSI to be used by AMR:

• When radio conditions are good, increases speech information.

• When radio conditions are bad, protects speech information.

> Full Rate: Alcatel implementation is fully compliant with GSM recommendations. All these AMR FR codec modes are supported. In particular, the Alcatel BSS has implemented the 7.95, 5.9 and 4.75 codec modes which use polynomials of constraint length 7 to ensure a high protection.

> Half Rate: Alcatel implementation supports 5 out of 6 AMR HR codec modes (AMR HR 7.95 is not supported) which are fully compliant with GSM recommendations. In particular, the Alcatel BSS has implemented the 4.75 codec mode which uses polynomials of constraint length 7 to ensure a high protection.

> During a call, only a subset out of these 8 codecs is used. The subset can include from 1 to 4 codecs. It is up to the operator to define its own codec subset. In particular, he can define a codec subset limited to the common codec modes supported by all the BSSs of its network (some BSSs may not be able to support all of them due to implementability problems).The codec subset defined by the operator is the same in the uplink and in the downlink.

> Codec Mode adaptation:

– dynamic change from one codec to another, using the same channel (FR or HR).

– metric used: C/I (Carrier over interference ratio).

> Channel Mode adaptation:

– change from one FR channel to an HR one and vice-versa independently from the codec mode.

– metric used: RX_QUAL uplink and downlink.

© Alcatel 141



• Based on adaptive trade-off between the share of throughput given to speech coding and the one given to channel coding (speech protection)

• Depends on radio conditions estimated in real-time

2.5 Handover DetectionAMR codec adaptation objective

Mediumradio conditions

Badradio conditions

Goodradio conditions

Speech coding = speech information

Channel coding = speech protection

> The AMR principle is to have a set of codecs and, for any radio conditions, to use the one with the best speech quality.

• Under good radio conditions, a codec with a high bit rate is used. Speech is encoded with more information so the quality is better. In the channel coding, only little place is left for redundancy.

• Under poor radio conditions, a codec with a low bit rate is chosen. Speech is encoded with less information, but this information can be well protected due to redundancy in the channel coding.

> The BSS adapts dynamically the codec in uplink direction and in downlink direction, taking into account the C/I measured by the BTS (for uplink adaptation) and by the MS (for downlink adaptation).

> The codec used in the uplink and used in the downlink can be different: the adaptation is independent in each direction.

> This permits to use an optimal codec for each C/I value of each direction, as indicated in the figure below.

C/I [dB]

SpeechQuality[dBQ]or

[MOS]

High bit rate (for example 12.2 kbit/s: EFR)

Medium bit rate (for example 7.95 kbit/s)

Low bit rate (for example 5.90 kbit/s)

AMR-FR with codec subset (12.2, 7.95, 5.90)

© Alcatel 142



2.5 Handover DetectionAMR: codec mode adaptation (1/3)

> Codec mode adaptation

• Only a subset out of these codecs can be used

• This subset may include from 1 to 4 codecs

• The same codec subset is used for both the Uplink and the Downlink

• Uplink codec mode adaptation:

– For each SACCH frame, the BTS compares C/I value to the threshold corresponding to the current codec (belonging to the codec subset defined by the operator)

• Downlink codec mode adaptation:

– Same process as uplink adaptation

– Nevertheless, the BTS remains the master

• Unrelated processes ⇒ uplink and downlink codecs may be different at a given time

© Alcatel 143



2.5 Handover DetectionAMR codec mode adaptation (2/3)

> The Codec mode can be modified on one frame out of two (CMI / CMC-CMR).

> Decision based on thresholds (OMC-R settable), for the uplink and the downlink

AMR_FR_THR_3 + AMR_FR_HYST

C/I norm

AMR_FR_THY_3


AMR_FR_THR_2

Low

High


AMR_FR_THY_3

CODEC_MODE_4(less robust)

CODEC_MODE_3

CODEC_MODE_2

CODEC_MODE_1(most robust)

© Alcatel 144



2.5 Handover DetectionAMR: codec mode adaptation (3/3)

Codec Mode Request(new codec mode)

Codec Mode Indication(new codec mode)

Codec Mode Request(new codec mode)

MS BTS TC


C/I evaluation &thresholds comparison


Codec Mode Command(new codec mode)

MS BTS TC


C/I evaluation &thresholds comparison

> Codec mode adaptation

• Uplink adaptation

• Downlink adaptation

© Alcatel 145



2.5 Handover DetectionAMR: codec and channel mode adaptation

> Codec mode adaptation is dynamically performed through a set of pre-defined “codec modes”:

– In FR mode:

– In HR mode:

> Choice between HR and FR (Channel mode adaptation) is done at callsetup and during call through HO causes 26 & 27


Channel coding

Speech coding


To endof chain

Fromacoustic part

22.8 Kbit/s (FR TS)

12.2 Kbit/s


6.7 Kbit/s


12.2 Kbit/s


6.7 Kbit/s



Channel coding

Speech coding


Fromacoustic part

To endof chain

11.4 Kbit/s (HR TS)7.4 Kbit/s6.7 Kbit/s5.9 Kbit/s




> Codec mode adaptation:

> The codec mode adaptation is the dynamic change from one codec to another codec, using the same channel (FR or HR). This adaptation is performed by the layer 1 of the BTS. It is transparent for the BSC and the layer 3 of the BTS.

> The metric used for codec mode adaptation is the evaluation of the ratio: signal over noise.

© Alcatel 146



2.5 Handover DetectionAMR gain

> AMR: always gives end user the best satisfaction

• Comparison between different codecs in terms of capacity and quality:

Speech quality

requirement

AMR-FR + AMR-HR

AMR-HR

AMR-FR

HR

EFR

FR

Capacity

requirement

> The main speech codec currently used in GSM networks, speech Full Rate, is quite old. It has been specified more than 10 years ago.

> Around 1992, to increase network capacity, GSM has specified a half rate speech codec. But this codec showed strong limitations in terms of speech quality, especially for mobile to mobile calls (double transcoding degrades very much the speech quality of the half rate codec) and under poor radio conditions.

> A few years later, when GSM started to be introduced in North America, American operators asked for an improved speech codec for full rate channels. Indeed speech quality was a major argument for customers used to have a good speech quality with analogsystems. For that issue, EFR was specified for GSM.

> Recently, studies on AMR have been launched to provide a solution to:

• Increase speech quality in full rate and half rate,

• Increase network capacity by offering a good half rate solution,

• Use a long-term solution, to avoid adding more and more codecs handled independently from the others,

• Take into account Tandem Free Operation (TFO), especially between MSs on half rate on one side and on full rate on the other side.

© Alcatel 147



> FR / HR discrimination

• Cell load AV_LOAD() computed from

– load samples = NB_BUSY_TS / NB_TS * 100

– non sliding window (LOAD_EV_PERIOD) averaging process

2.5 Handover DetectionAMR: TCH allocation

AV_LOAD

Time

THR_FR_LOAD_U_SV1 = 80%

THR_FR_LOAD_U_SV3 = 60%

THR_FR_LOAD_L_SV1 = 50%

THR_FR_LOAD_L_SV3 = 40%

100%

FR for any MS

HR for AMR MSFR for other MS

HR for any MS

HR for AMR MSFR for other MS

FR for any MS

THR_FR_LOAD_U_SV1=

THR_FR_LOAD_U_SV3=

THR_FR_LOAD_L_SV1=

THR_FR_LOAD_L_SV3=

> Load samples are computed by the BSC every TCH_INFO_PERIOD = 5 seconds.

> LOAD_EV_PERIOD is the averaging window size for cell load computation. It is equal to 12 but can be changed at the OMC-R level on a per cell basis.

> Therefore cell load process has a periodicity of 1mn by default (TCH_INFO_PERIOD*LOAD_EV_PERIOD).

> The allocation of Half rate resources is decided upon the load evaluation in the serving cell.

> AMR HR (HR SV3) offers a better speech quality than HR SV1. The Alcatel BSS offers thus the possibility to define a set of thresholds specific for AMR. If the load increases, AMR HR capable MSs can be the first to be allocated in HR (HR SV3) for load reasons, and if the load still increases, then all the HR capable MSs can be allocated in HR (HR SV1 & HR SV3) for load reasons.

• This is why two variables of load are defined: LOAD_SV3 and LOAD_SV1.

> Each load variable is calculated through its own threshold set: the thresholds related to the variable LOAD_SV3 (THR_FR_LOAD_U_SV3 and THR_FR_LOAD_L_SV3) are less restrictive than the ones related to the variable LOAD_SV1 (THR_FR_LOAD_U_SV1 and THR_FR_LOAD_L_SV1).

• As a consequence, if the load of the cell increases, then the variable LOAD_SV3 will first equal TRUE, and if the load still increases, the variable LOAD_SV1 will then equal TRUE.

> The variable LOAD_SV1 corresponds to a level of load where it is important to put as many MSs on half rate TCH as possible: HR SV3 or HR SV1.

> The same computation is done to compute LOAD_SV3 with the thresholds: THR_FR_LOAD_U_SV3 and THR_FR_LOAD_L_SV3 with the following relations:

• THR_FR_LOAD_L_SV3 ≤ THR_FR_LOAD_U_SV3

• THR_FR_LOAD_U_SV3 ≤ THR_FR_LOAD_U_SV1

• THR_FR_LOAD_L_SV3 ≤ THR_FR_LOAD_L_SV1

Previous stateAV_LOAD

LOAD_SV1 = FALSE LOAD_SV1 = TRUE

AV_LOAD ≤ THR_FR_LOAD_L_SV1 LOAD_SV1 = FALSE LOAD_SV1 = FALSE

THR_FR_LOAD_L_SV1 <

AV_LOAD ≤

THR_FR_LOAD_U_SV1

LOAD_SV1 = FALSE LOAD_SV1 = TRUE

THR_FR_LOAD_U_SV1 < AV_LOAD LOAD_SV1 = TRUE LOAD_SV1 = TRUE

© Alcatel 148



2.5 Handover DetectionCause 26: AMR HR to FR HO (1/4)

> CAUSE 26: AMR channel adaptation HO (HR to FR)

• Cause 26 is triggered if :

– Current channel rate is HR

– Current channel is dual rate and changes are allowed

– AMR_FR speech codec is allowed:

� EN_AMR_FR = ENABLE

© Alcatel 149




> CAUSE 26: AMR channel adaptation HO (HR to FR) equation

> [ a previous intracell HO cause 15 or 16 has been triggered for this call in the serving cellOREN_INTRA_DL_AMR = DISABLE and EN_INTRA_UL_AMR = DISABLE]

> ANDAV_RXQUAL_UL_CA_HR_FR > THR_RXQUAL_CA + OFFSET_CA+ OFFSET_RXQUAL_FH and AV_RXLEV_UL_HO > RXLEV_UL_IHORAV_RXQUAL_DL_CA_HR_FR > THR_RXQUAL_CA + OFFSET_CA+ OFFSET_RXQUAL_FH and AV_RXLEV_DL_HO > RXLEV_DL_IH

> AND EN_AMR_CA = ENABLE

> Size of window for averaging quality: A_QUAL_CA_HR_FR

© Alcatel 150





• THR_RXQUAL_CA and OFFSET_CA are set as follows :

if LOAD_SV3(0) = false then

THR_RXQUAL_CA = THR_RXQUAL_CA_NORMAL

OFFSET_CA = OFFSET_CA_NORMAL

if LOAD_SV3(0) = true then

THR_RXQUAL_CA = THR_RXQUAL_CA_HIGH

OFFSET_CA = OFFSET_CA_HIGH

© Alcatel 151





• Calculation of LOAD_SV3(0):

If previous value of LOAD_SV3 = false then

If AV_LOAD > THR_FR_LOAD_U_SV3 thenLOAD_SV3 = true

Else LOAD_SV3 = false

Else (if previous value of LOAD_SV3 = true then)

If AV_LOAD <= THR_FR_LOAD_L_SV3 thenLOAD_SV3 = false

Else LOAD_SV3 = true

Annex 3

© Alcatel 152



2.5 Handover DetectionCause 27: AMR FR to HR HO (1/2)

> CAUSE 27: AMR channel adaptation HO (FR to HR)

> Cause 27 is triggered if :

– Current channel rate is FR

– Current channel is dual rate and changes are allowed

– AMR_HR speech codec is allowed:

� EN_AMR_HR = ENABLE

© Alcatel 153



2.5 Handover DetectionCause 27: AMR FR to HR HO (2/2)

> CAUSE 27: AMR channel adaptation HO (FR to HR) equation

> AV_RXQUAL_UL_CA_FR_HR <= THR_RXQUAL_CA+ OFFSET_RXQUAL_FH

> ANDAV_RXQUAL_DL_CA_FR_HR <= THR_RXQUAL_CA

+ OFFSET_RXQUAL_FH

> AND EN_AMR_CA = ENABLE

> Size of window for averaging quality: A_QUAL_CA_FR_HR

© Alcatel 154



2.5 Handover DetectionCause 26 & 27 interworking

> Cause 26 & 27 interaction

THR_RXQUAL_CA_NORMAL

Quality

THR_RXQUAL_CA_NORMAL +OFFSET_CA_NORMAL

THR_RXQUAL_CA_HIGH

THR_RXQUAL_CA_HIGH +OFFSET_CA_HIGH

Bad quality: 7

Bad quality: 7

Load = False Load = True

Half Rate

Full Rate

Half Rate

Full Rate

HO cause 26

HO cause 27

HO cause 26

HO cause 27

© Alcatel 155



2.5 Handover DetectionIntroduction to TFO (1/2)

> Tandem Free Operation (TFO) solution

TC TC

Codec GSM (A)(8 or 16 Kbit/s)

MS A MS B

Codec GSM (B)(8 or 16 Kbit/s)

A/µ law(64 Kbit/s)

Double transcoding without TFO

TC TC

Codec GSM (A)(8 or 16 Kbit/s)

MS A MS B

No transcoding withTFO

> The Tandem Free Operation (TFO) feature is a way to avoid double transcoding in mobile to mobile speech calls.

> Indeed without TFO, one GSM codec type is used between the first mobile and the first transcoder, then the speech is transcodedinto A/µ law between transcoders and finally this speech is transcoded again into a second GSM codec type (which may be the same as the first one) between the second transcoder and the second mobile.

> With TFO, after call establishment, both BSSs at each side are able to negotiate a common GSM codec type which is then used from one mobile to the other mobile. This negotiation is performed through in-band signaling between transcoders.

© Alcatel 156



2.5 Handover DetectionIntroduction to TFO (2/2)

> Applicability: Only MS to MS speech calls

> TFO is based on information exchanged between transcoders

TRAU

MS MSBTS

64 Kbit/s Speech Sample carrying:

- TFO frames on the LSB containing: - compressed speech samples - control bits - TFO messages

- original PCM speech samples on the MSB

TRAU

BSC

IPE

MSC

IPE

MSC

BTS

BSC

© Alcatel 157



2.5 Handover DetectionTFO principles

> In the case of first allocation (normal assignment at call setup, inter-BSS handover, intra-BSS handover where no TFO was previously on-going):

Exchange of Codec capabilities

New call setup

Match

Found

Yes No

Look for common codec

NoYes

Normal operationTFO mode ON

Intracell HO

© Alcatel 158



2.5 Handover DetectionCause 29: TFO HO

> CAUSE 29: TFO HO

• Intracell HO used in case of codec mismatch between two MSscalling, in order to match their speech codec

• No radio measurements needed � No priority and may be triggered at any time

• Conditions:

HO_INTRACELL_ALLOWED = ENABLEAND

EN_TFO_MATCH = ENABLE

© Alcatel 159



2.5 Handover DetectionCause 29: TFO parameters (1/5)

> EN_TFO

– enables/disables the feature, per cell

> EN_TFO_MATCH

– enables/disables resolution of codec mismatch, per cell

> EN_TFO_OPT

– enables/disables codec optimization, per cell

> FORCE_TFO_VS_AMR

– enables/disables the basic functions of TFO for GSM EFR, FR and HR codec types when the current codec is AMR FR or AMR HR

> FORCE_TFO_HR_WHEN_LOADED

– controls the establishment of TFO in HR when the cell is loaded

> KEEP_CODEC_HO

– indicates if the BSC tries to keep the same codec in case of internal intercell HO

> Codec mismatch:

• At call setup for a mobile to mobile speech call, when both BSSs do not use the same codec type, a codec mismatch occurs. If a common codec type can be found, either one or possibly both BSSs perform an intracell handover to use the common codec type found. Afterwards TFO can be started using this common codec type. Codec mismatch resolution is authorized in the BSC using an O&M flag: EN_TFO_MATCH. This flag is forwarded to the TC, via the BTS.

> Codec optimization:

• At call setup for a mobile to mobile speech call, it can occur that a first common codec type can be found but a better speech quality would be provided with another common codec type. Once both BSSs operate in Tandem Free, they exchange their complete codec capabilities, to try to find a better codec type than the current one. Codec optimization is authorized in the BSC using an O&M flag : EN_TFO_OPT. This flag is forwarded to the TC, via the BTS.

> Classification of codec types :

• In all cases, TFO is considered better as any tandeming configuration. In TFO, EFR is considered as better than FR, considered as better than HR.

> Force TFO vs. AMR :

• TFO + AMR is not supported in this implementation of TFO. In the normal operation, a call established with AMR will not initiate a TFO negotiation. The goal of the function Force TFO vs. AMR is to allow a call, established with AMR to initiate a TFO negotiation and, if possible, to change of codec type to FR, HR or EFR to establish TFO.

> In-Path Equipments (IPEs):

• TFO can only be activated if TFO frames (at 8 or 16 Kbit/s) can be sent transparently through the public switching network. In-path equipments are equipments such as echo cancelers or A/µ law converters that modify the 64 Kbit/sspeech signal. Such equipments need to be deactivated for TFO calls.

© Alcatel 160




> EN_TFO_OPT: enables/disables codec optimization, per cell

• Allows new TFO negotiation on an on-going MTM call to find a better common codec

– For example, HR is used at both sides, but FR is possible too

– HO cause 29 will be triggered on both sides towards best codec

© Alcatel 161




> FORCE_TFO_VS_AMR:

• TFO AMR not specified

– Call setup in AMR is not followed by TFO negotiation

– FORCE_TFO_VS_AMR enables HO cause 29 after AMR call establishment towards best TFO codec

ERF + TFOThe MS A can only use HR/EFR/FR

The MS B can use HR/EFR/FR

Cell cap:AMR/HR/EFR/F

RCell cap:HR/EFR/FR

The MS A using AMR, could use HR/EFR/FR


MS A MS B

TFO not possible

Enable (Alcatel patent)

FORCE_TFO_VS_AMR

Disabled(ETSI implementation)

© Alcatel 162




> FORCE_TFO_HR_WHEN_LOADED:

• Gives control on load regulation precedence vs. TFO

– 3 values: TFO_HR_NOT_FORCED, TFO_HR_ONLY, TFO_HR_PREFERRED enable different behaviours in case of loaded cell

HR + TFOThe MS A can only use HR


Loaded cellMS/cell cap:

Unloaded cellMS/cell cap:

The MS A can use HR/EFR/FR


MS A MS B

EFR + TFO

Enable (Alcatel patent)

FORCE_TFO_HR_WHEN_LOADED

Disabled(ETSI implementation)

H/EFR/FR HR/EFR/FR

© Alcatel 163




> KEEP_CODEC_HO

• keeps the same codec type in the new cell in case of internal

intercell HO in order to avoid resolving a new mismatch codec

situation

• Avoids double speech quality transition:

TFO --> non-TFO --> TFO

• 3 possible behaviors:

– TFO_CALLS_ONLY: codec is preferably kept in case of

internal intercell HO for TFO calls only

– ALL_CALLS: codec is preferably kept in case of internal

intercell HO for all calls (whatever the TFO state)

– FREE: the choice of the codec type is free and depends on

the situation in the target cell

© Alcatel 164



2.5 Handover DetectionCause 30: Move from PS to CS zone

> If EN_RETURN_CS_ZONE_HO = enable

> AND a CS call is inside both

• The Non pre-emptable zone and

• The MAX_SPDCH_LIMIT_ZONE then

> An intra cell HO cause 30 is triggered

TRX3 TRX1

BCCH SDCCHPS PS PS PSCS CS CS

Non pre-emptable zone

MAX_SPDCH_HIGH_LOAD zone

MAX_SPDCH_LIMIT zone

PS traffic zone

HO cause 30

PS PS

B9

> The enabling/disabling of Cause 30 is independent of the flag HO_INTRACELL_ALLOWED.

> MAX_SPDCH_HIGH_LOAD zone: this zone corresponds to the MAX_SPDCH_HIGH_LOAD consecutive PS capable timeslots that are preferred for PS allocation. In this zone, allocated TBFs cannot be pre-empted. If the value of MAX_SPDCH_HIGH_LOAD is not modified, this zone remains unchanged.

> Non pre-emptable PS zone: this zone is always inside the MAX_SPDCH_HIGH_LOAD zone. In this latter zone, we search for the rightest timeslot allocated to the MFS and used. Then, all timeslots situated at its left define this non pre-emptable PS zone.

> MAX_SPDCH_LIMIT zone: this zone corresponds to the MAX_SPDCH_LIMIT consecutive PS capable timeslots that are preferred for PS allocation.

> PS traffic zone: this zone corresponds to the larger zone between the non pre-emptable PS zone and the MAX_SPDCH_LIMIT zone.

© Alcatel 165



2.5 Handover DetectionHandover causes priorities

Emergency Handover

Uplink Quality Cause 2

Downlink Quality Cause 4

Uplink Level Cause 3

Downlink Level Cause 5

Distance Cause 6

Too Low Level UL Inner Cause 10

Too Low Level DL Inner Cause 11

HR to FR Channel Adaptation Cause 26 intracell

Uplink Interference Cause 15 intracell

Downlink Interference Cause 16 intracell

Better Condition Handover

Capture Handover Cause 24

Power Budget Cause 12

Traffic Cause 23

Outer UL/DL Level Cause 13

FR to HR Channel Adaptation Cause 27 intracell

Forced Directed Retry Cause 20

Fast Traffic HO Cause 28

HANDOVER PRIORITIES

TFO

Move from PS to CS Zone

29

30

> The causes 24, 12 and 23 have the same priority. Nevertheless, if a cell is a candidate for both causes, triggered in the same time, it is kept only for cause 12.

> Dealing with all available causes, we get the following list:

• Emergency: 7 > 17 > 18 > 2 > 4 > 3 > 5 > 6 > 22 > 10 > 11 > 26 > 15 > 16

• Better conditions: 21=14=24=12=23 > 13 > 27 > 20 > 28

• 29 has no priority

© Alcatel 166



> Emergency causes

1- What is the HO cause 2?

2- Which is the flag to activate the HO cause 2?

2.5 Handover DetectionTraining exercises (1/16)

Time allowed:

45 minutes

© Alcatel 167



> Emergency causes

Complete the diagram below and fill in the chart with:

L_RXQUAL_UL_H = 3

RXLEV_UL_IH = -70 dBm

P=MS_TXPWR_MAX=33dBm


Quality

Level

Nb of case

AV_RXQUAL_UL_HO

AV_RXLEV_UL_HO

Current MS power

HO cause 2: YES/NO?

1 2 3 4 5 6

4 1 3 4 4 4

-81 -79 -75 -70 -69 -72

33 33 33 33 3329

(0.8 w)

© Alcatel 168




> Better condition causes (simple case)

• There are only 2W cells and 2W MS

• EN_TRAFFIC_HO(0,n) =Disable

• No Ping-Pong margin

• HO_MARGIN(0,n) =5 dB

• NO DL PC,RXLEV_LIMIT_PBGT_LIMIT=-47dBm,The serving is not a concentric cell.

> Fill up the chart:

Serving cell N cell

Nb of case

AV_RXLEV_NCELL(n)

AV_RXLEV_PBGT_HO

PBGT(n)

HO cause 12: YES/NO?

1 2 3 4 5 6

-70 -70 -80 -70 -70 -75

-80 -70 -75 -75 -79 -96

© Alcatel 169




> Better condition causes (ping-pong case)

• EN_TRAFFIC_HO(0,n) =Disable

• Ping-Pong marginPING_PONG_HCP=15dbT_HCP =15s

• HO_MARGIN(0,n) =5 dBA_PBGT_HO = 8 SACCHA n to 0 HO has just been triggered, what happens after 4s?

N cellServing cell

?

Nb of case

AV_RXLEV_NCELL(n)

AV_RXLEV_PBGT_HO

PBGT(n) «a» only

HO cause 12: YES/NO? PBGT>HO margin

PING_PONG_HCP=15 -> PBGT(n)

HO cause 12:YES/NO?

1 2 3 4 5 6

-70 -70 -80 -70 -70 -75

-80 -70 -75 -75 -79 -96

10 0 -5 5 9 21

YES NO NO NO YES YES

© Alcatel 170



2.5 Handover DetectionTraining exercise (5/16)

> Training exercise: Handover Detection

• Better condition causes (traffic case)

• EN_TRAFFIC_HO(0,n) =Enable

• No Ping-Pong margin

• HO_MARGIN(0,n) =5 dB

• DELTA_DEC_HO_margin =5dB

• DELTA_INC_HO_margin =5dB N cellServing cell

HO

© Alcatel 171



> Better condition causes (traffic case)

Fill up the chart:


N cellServing cell

HO ?

Nb of case

AV_RXLEV_NCELL(n)

AV_RXLEV_PBGT_HO

Traffic distribution

PBGT(n)

DELTA_HO_MARGIN (0, n)

Cause 12 HO: YES/NO?

Cause 23 HO: YES/NO?

1 2 3 4

-71 dBm -71 dBm -76 dBm -71 dBm

-780 dBm -80 dBm -80 dBm -80 dBm

0: traffic lowN: traffic high

0: traffic highN: traffic low

0: traffic highN: traffic low

0: traffic lowN: traffic high

© Alcatel 172




> Channel adaptation (cause 26 and cause 27)

1- Why is it recommended to have A_QUAL_CA_FR_HR ≥

A_QUAL_CA_HR_FR ?

2- An operator may be willing to:

- Under normal load, use only HR calls for quality 0

- Under high load, use HR calls for qualities 0 to 3, with an hysteresis of 1

Find the thresholds and offsets for normal and high load:

THR_RXQUAL_CA_NORMAL = ? OFFSET_CA_NORMAL = ?

THR_RXQUAL_CA_HIGH = ? OFFSET_CA_HIGH = ?

© Alcatel 173




> Channel adaptation (cause 26 and cause 27)

• EN_INTRA_XX_AMR = Disable

• RXLEV_XX_IH = -110 dBm

• OFFSET_RXQUAL_FH = 0

• A_QUAL_CA_FR_HR =4 and A_QUAL_CA_HR_FR = 2

> Use the previous thresholds and fill up the chart:

UL_QUAL 0 1 2 3 3 1 1 0 0 1

DL_QUAL 0 0 1 1 1 0 0 2 4 3

LOAD_SV3 False False False False True True True True True True

AV_RXQUAL_UL_CA_HR_FR

AV_RXQUAL_DL_CA_HR_FR

AV_RXQUAL_UL_CA_FR_HR

AV_RXQUAL_DL_CA_FR_HR

CHANNEL TYPE FR FR FR

© Alcatel 174




> Capture HO (Cause 24 )

• There are only 2W cells and 2W MS

• L_RXLEV_CPT_HO(0,n) = -85dBm

• EN_GENERAL_CAPTURE_HO = ENABLE

>

> Fill up the chart: N cellServing cell

HO ?

Nb of case 1 2 3 4 5 6

AV_RXLEV_NCELL(n) - 70 - 70 - 80 - 70 - 70 - 85

CAPTURE_TRAFFIC_CONDITION NOT_LOW HIGH ANY_LOAD HIGH HIGH HIGH

TRAFFIC_LOAD(0) HIGH LOW INDEFINITE HIGH LOW HIGH

TRAFFIC_LOAD(n) HIGH LOW INDEFINITE LOW LOW LOW

HO cause 24: YES/NO?

© Alcatel 175




> Fast Traffic HO (cause 28)

> Find the appropriate candidate MS for this queued request:

• Channel rate required: HR

• L_RXLEV_NCELL_DR(n) = -85 dBm (whatever n)

• FREElevel_DR(n) = 1 (whatever n)

• Channel rate: MS1�FR on Full rate TRX, MS2�HR, MS3�FR on Dual rate TRX

• t(n) for neighbor cells: t(1)=1, t(2)=2, t(3)=2

• AV_RXLEV_NCELL(n) in dBm:

Neighbors

MS 1

MS 2

MS 3

1 2 3

- 82 dBM

- 79 dBM

- 90 dBM

- 85 dBM

- 86 dBM

- 82 dBM

- 78 dBM

- 92 dBM

- 89 dBM

© Alcatel 176




> TFO HO (cause 29): after call setup

Find the 2 speech version types of the following MS to MS call

• EN_TFO = enable, EN_TFO_MATCH = enable

• FORCE_TFO_HR_WHEN_LOADED = TFO_HR_NOT_FORCED



MS A MS B

TCH = ? TCH = ?

TCH = ? TCH = ?

Aftercall setup

After TFOnegociation

HR/EFR/FR EFR/FR

© Alcatel 177







• FORCE_TFO_HR_WHEN_LOADED = TFO_HR_ONLY



MS A MS B

TCH = ? TCH = ?

TCH = ? TCH = ?

Aftercall setup


HR/EFR/FR EFR/FR

© Alcatel 178







• FORCE_TFO_HR_WHEN_LOADED = TFO_HR_PREFERRED



MS A MS B

TCH = ? TCH = ?

TCH = ? TCH = ?

Aftercall setup


HR/EFR/FR EFR/FR

© Alcatel 179










MS A MS B

TCH = ? TCH = ?

TCH = ? TCH = ?

Aftercall setup


HR/EFR/FR HR/EFR/FR

© Alcatel 180




> TFO HO (cause 29): after handover

Find the speech version types of the following MS to MS call



1. KEEP_CODEC_HO = TFO_CALLS_ONLY

2. KEEP_CODEC_HO = FREE

??



MS 1


MS 2

HO

?

MS 2Call setup +

TFO negociation

MS 2HO

?TFO

?TFO

HR/EFR/FR HR/EFR/FR HR/EFR/FR

© Alcatel 181



??



MS 1


MS 2

HO

?

MS 2Call setup +

TFO negociation

MS 2HO

?TFO

?TFO

HR/EFR/FR HR/EFR/FR HR/EFR/FR


> TFO HO (cause 29): after handover

Find the speech version types of the following MS to MS call



• KEEP_CODEC_HO = TFO_CALLS_ONLY

1. EN_TFO_OPT = disable

2. EN_TFO_OPT = enable

© Alcatel 182



2.6 Handover Candidate Cell Evaluation





Handover Detection


Handover Management

Exercise

© Alcatel 183



> Used to rank potential target cells:

• Ranking based on radio characteristics

• Ranking based on operator preferences

• Ranking based on traffic intensity

2.6 Handover Candidate Cell EvaluationPrinciples

Radio

Link

Measurements

Active

Channel

Pre-processing

BTS BSC

HO DetectionHO Candidate

Cell Evaluation

HO

management

MSC

HO

protocol

HO Preparation

> Handover candidate cell evaluation

• The process is performed in the BSC.

• Once a need for handover is detected, this process looks for possible target cells (except if it is an intracell handover or an interzone handover) and provides the BSC entity in charge of the HO decision and execution entity with a list of candidate cells and their respective HO cause.

© Alcatel 184



2.6 Handover Candidate Cell EvaluationEvaluation process

Measurement

Preprocessing

A_LEV_HO

A_QUAL_HO

A_PBGT_HO

A_RANGE_HO

HO Detection

Cause 2: uplink quality

Cause 3: uplink level

Cause 4: downlink quality

Cause 5: downlink level

Cause 6: distance

Cause 12: power budget

Performed every SACCHPerformed every SACCH

Pre-ranking

Priority (0, n) = 0

Cell 2: cause C2

Cell 3: cause C2

Cell 4: cause C2

Priority (0, n) = 1

Cell 1: cause C2

Priority (0, n) = 2

Priority (0, n) = 3

Cell 5: cause C2

Cell 6: cause C2

Cell 7: cause C2

Cell 8: cause C2

Priority (0, n) = 4

Priority (0, n) = 5

Priority (0, n) = 0

Cell 2: cause C2

Cell 3: cause C2

Cell 4: cause C2

Priority (0, n) = 1

Priority (0, n) = 2

Priority (0, n) = 3

Cell 6: cause C2

Cell 8: cause C2

Priority (0, n) = 4

Priority (0, n) = 5

PBGT filteringHO_MARGIN_XX(0,n)

Grade

Priority (0, n) = 0

Cell 4: cause C2

Cell 2: cause C2

Cell 3: cause C2

Priority (0, n) = 1

Priority (0, n) = 2

Priority (0, n) = 3

Cell 6: cause C2

Cell 8: cause C2

Priority (0, n) = 4

Priority (0, n) = 5

Order

Priority (0, n) = 0

Cell 4: cause C2

Cell 3: cause C2

Cell 2: cause C2

Priority (0, n) = 1

Priority (0, n) = 2

Priority (0, n) = 3

Cell 6: cause C2

Cell 8: cause C2

Priority (0, n) = 4

Priority (0, n) = 5

Cell evaluation process (Order or Grade)

HO Candidate Cells Evaluation

Max

every SACCH

Preprocess

measurement

Measurement

resultRaw cell list

Cell 1: cause C2

Cell 2: cause C2

Cell 3: cause C2

Cell 4: cause C2

Cell 5: cause C2

Cell 6: cause C2

Cell 7: cause C2

Cell 8: cause C2

... max 32 cells

> The HO candidate evaluation process is run after all intercell handover alarms.

> In case of intracell handover alarm (HO causes 10, 11, 13, 15, 16), the candidate cell evaluation process is skipped: the target cell is the serving cell.

> The handover detection gives as indication the raw cell list (built from book-keeping list) and the preferred layer for the handover. In case of emergency handover alarms or cause 20 alarm, the cell evaluation will order the cells given in the raw list, putting in the first position the cells belonging to the preferred layer, having the highest priority (if EN_PRIORITY_ORDERING=ENABLE) and/or having the same frequency band type as the serving cell. In case of an intercell handover alarm, if the serving cell belongs to the raw cell list (emergency handover from the DCS 1800 inner zone of a multiband cell), this cell is put at the end of the candidate cell list with the MS zone indication OUTER.

> In case of better condition handover alarms (except cause 20), the cell evaluation will order the cells given in the raw list, putting in the first position the cells belonging to the preferred layer and having the highest priority (if EN_PRIORITY_ORDERING=ENABLE).

© Alcatel 185



> Pre-ranking in hierarchical or multi-band networks:

2.6 Handover Candidate Cell EvaluationPre-ranking

Priority(0,n) = 0Cell_layer_type = Pref_layer

Cell_band_type = serving_cell

Priority(0,n) = 1

Priority(0,n) = 5

Cell_band_type = serving_cell

Priority(0,n) = 0Cell_layer_type = Pref_layer

Priority(0,n) = 1

Priority(0,n) = 5

List ofcandidatecells n

© Alcatel 186



2.6 Handover Candidate Cell EvaluationPre-ranking

> with priority(0,n) settings, the operator can, for each couple of cells:

• tag the target cell with a defined priority (from 0 = max to 5 = min)

• this definition has an higher priority than usual order/grade ranking

> especially useful for multi band/hierarchical architectures:

• a simple way to force a target cell whatever its RxLev level and PBGT

• nevertheless can be skipped over by filtering processes

• low interest for standard networks

RxLev: - 90 dBmPBGT: + 5 dB

Serving cell

Candidate cell 1

Candidate cell 2

RxLev: - 70 dBmPBGT: + 10 dB

Priority

P1

P0

> Cell ordering according to target layer and target band

> In hierarchical or multiband environment, cells are characterized by the layer they belong to or/and the frequency band they use. The candidate cell evaluation process takes into account these characteristics in the candidate cell ordering.

> In hierarchical environment, the HO detection process can indicate a preferred layer where the handover must be directed to. If this indication is used, the candidate cell evaluation puts in the first places of the list, the candidate cells belonging to the preferred layer. They are followed by the cells of the other layer, providing they are also correct candidates.

> After this possible distinction, in each part of the list, the candidate cell evaluation sorts the candidate cells according to the parameter PRIORITY(0,n) (parameter on line changeable from the OMC-R).

> The cells having the highest priority are put in the first place of the list. They are followed by the cells having the lowest priorities. The PRIORITY(0,n) is only used when the flag EN_PRIORTY_ORDERING is set to “enable”.

> In case of emergency handover, for each category (preferred layer and other layer) and between cells having the same priority, the candidate cell evaluation sorts the candidate cells according to the frequency band they use: the cells which use the same frequency band as the serving cell are put first and they are followed by the cells which use the other frequency band.

> The cell evaluation function is then applied to the different candidate cell lists defined from the preferred layer indication, the PRIORITY(0,n) parameter and the frequency band of the serving cell (only in case of emergency handover).

© Alcatel 187



2.6 Handover Candidate Cell EvaluationPBGT Filtering

> PBGT filtering:

• optional, flag EN_PBGT_FILTERING

• filter out cells from the target list

• inhibited for better cell handovers

• based on power budget

• per couple of cells

• was needed for multiband architecture

• PBGT(n) > HO_MARGIN_XX (0,n) + OFFSET_HO_MARGIN_INNER

– HO_MARGIN_XX (0,n) = HO_MARGIN_QUAL (0,n)for cause 2,4

– HO_MARGIN_XX (0,n) = HO_MARGIN_LEV (0,n) for cause 3,5

– HO_MARGIN_XX (0,n) = HO_MARGIN_DIST (0,n) for cause 6

– OFFSET_HO_MARGIN_INNER is only applied when the MS is in the inner zone of a concentric or multi band cell

– The averaging window is A_PBGT_HO

> The filtering process allows to filter out cells from the target list before sending them to the ORDER or GRADE evaluation process.

> It can be enabled/disabled on-line on a per cell basis from the OMC-R with the flag EN_PBGT_FILTERING.

> The candidate cells are filtered on their power budget in relation to a handover margin threshold based on the handover cause.

Note: the averaging window used for this process is A_PBGT_HO (even for emergency handovers, where a handover alarm could have been raised through A_LEV_HO or A_QUAL_HO samples)

© Alcatel 188



> ORDER cell evaluation processCell "n" is ranked among other accordingly:

If EN_LOAD_ORDER = ENABLE and cell n is internal to the BSCORDER (n) = PBGT(n) + LINK_FACTOR(0,n) + FREEfactor(n)- FREEfactor(0)- HO_MARGIN_XX(0,n)

• Link_factor (0,n) is an operator parameter to give a bonus/penalty to a cell

ex: avoid external HO, decrease incoming flow of HO to a cell from another

• FREEfactor is TCH traffic based bonus/penalty to rank cellsIf EN_LOAD_ORDER = DISABLE or cell n is external to the BSC

ORDER (n) = PBGT(n) + LINK_FACTOR(0,n) - HO_MARGIN_XX(0,n)

Cell "n" is kept if:• AV_RXLEV_NCELL (n) > RXLEVmin (n)

+ max [0;(MS_TXPWR_MAX(n)-P)] [dBm]

2.6 Handover Candidate Cell EvaluationORDER evaluation

> Two types of cell evaluation algorithms can be used: ORDER and GRADE.

> ORDER and GRADE are two different methods of cell ranking. They both consist in giving a mark or ’figure of merit’ to each candidate cell.

> The basic differences between ORDER and GRADE are that:

• with ORDER

– The candidate cell evaluation process interacts with the handover detection by use of cause-dependent handover margins.

– The candidate cell evaluation process takes into account the number of free TCHs in the candidate cells.

• with GRADE

– The candidate cell evaluation process does not interact with the handover detection.

– The candidate cell evaluation process takes into account the relative load of traffic channels in the candidate cells.

> The type of cell evaluation is chosen by the operator on a (serving) cell basis and is provided to the BSC with the parameter CELL_EV.

> For any handover cause, the first cell in the list is taken as a target cell, i.e. the cell with the highest value of ORDER(n). The cells do not need to fulfil any other condition.

> If no cell fulfils the condition and the serving cell does not belong to the target cell list, the target cell list is empty and no further action is carried out.

Note: the A_PBGT_HO averaging window is used for this process.

© Alcatel 189



> GRADE cell evaluation processCell "n" is ranked among other accordingly:

If EN_LOAD_ORDER = ENABLE and cell n is internal to the BSCGRADE (n) = PBGT(n) + LINK_FACTOR(0,n) + LOADfactor(n)

• Link_factor (0,n) is an operator parameter to give a bonus/penalty to a cell

• LOADfactor(n) is a weighting factor that takes into account the relative load of traffic channels in a cell

If EN_LOAD_ORDER = DISABLE or cell n is external to the BSC

GRADE (n) = PBGT(n) + LINK_FACTOR(0,n)> Cell "n" is kept if:

• AV_RXLEV_NCELL (n) > RXLEVmin(n)+ max [0;(MS_TXPWR_MAX(n)-P)]

2.6 Handover Candidate Cell EvaluationGRADE Evaluation

Annex 4

> LINKfactor(0,n) is a parameter set by OMC command for each cell(n).

> LINKfactor(n1,n2) allows the operator to handicap or to favor the cell n1 with respect to its neighbor cell n2. In particular, it can be used to disadvantage an external cell when an internal cell is also a possible candidate.

> For any handover cause, the first cell in the list is taken as a target cell, i.e. the cell with the highest value of GRADE(n). If no cell fulfils the condition and the serving cell does not belong to the target cell list, the target cell list is empty and no further action is carried out.

Note: the A_PBGT_HO averaging window is used for this process

© Alcatel 190



2.6 Handover Candidate Cell EvaluationTraining exercise (1/2)

> Emergency HO detected

• With the “Candidate evaluation.xls” excel sheet...

» Filtering simulation for a list of candidate cells

» Ranking simulation for a list ofcandidate cells

Candidate Cell Evaluation

Serving cell Cell 1 Cell 2 Cell 3 Cell 4 Cell 5 Cell 6

RxLev_cell1Mk RxLev_DL Cell_Nb1 BSIC_cell1 Cell_Nb2 BSIC_cell2RxLev_cell2 Cell_Nb3 BSIC_cell3RxLev_cell3 Cell_Nb4 BSIC_cell4RxLev_cell4 Cell_Nb5 BSIC_cell5RxLev_cell5 Cell_Nb6 BSIC_cell6RxLev_cell6

-102** 0 0 -110 0 0 -110 0 0 -110 0 0 -110 0 0 -110-99** 0 0 -110 0 0 -110 0 0 -110 0 0 -110 0 0 -110-99** 0 0 -110 0 0 -110 0 0 -110 0 0 -110 0 0 -110

-98AssCmd 0 0 -110 0 0 -110 0 0 -110 0 0 -110 0 0 -110

-110AssCmp 0 0 -110 0 0 -110 0 0 -110 0 0 -110 0 0 -110

-76** 0 0 -110 0 0 -110 0 0 -110 0 0 -110 0 0 -110

-96** 0 0 -110 0 0 -110 0 0 -110 0 0 -110 0 0 -110

-95** 14 3 -91 0 0 -110 0 0 -110 0 0 -110 0 0 -110-93** 14 3 -92 0 0 -110 0 0 -110 0 0 -110 0 0 -110

-93** 1 0 -89 14 3 -91 0 0 -110 0 0 -110 0 0 -110

-93** 1 0 -90 14 3 -94 0 0 -110 0 0 -110 0 0 -110-93** 1 -0 -88 14 3 -94 3 1 -101 0 0 -110 0 0 -110

-94** 8 7 -93 1 0 -93 14 3 -96 3 1 -103 0 0 -110-96** 1 0 -93 8 7 -95 14 3 -99 3 1 -106 0 0 -110

-96** -1 0 -91 8 7 -95 14 3 -99 3 1 -104 0 0 -110-98** 1 0 -92 14 3 -98 8 7 -99 3 1 -107 0 0 -110

-101** 8 7 -97 1 0 -97 14 3 -102 3 1 -107 0 0 -110

-101HOCMD 8 7 -96 1 0 -99 14 3 -103 3 1 -108 0 0 -110

0 0 -1100 0 -1100 0 -110

0 0 -110

0 0 -110

0 0 -110

0 0 -110

0 0 -1100 0 -110

0 0 -110

0 0 -1100 0 -110

0 0 -1100 0 -110

0 0 -1100 0 -110

0 0 -110

0 0 -110

HO Cause

A_PBGT_HO

GRADE EVALUATION

Priority(0,n)

HO_MARGIN_LEV(0,n)

RX_LEV_MIN(n)

LINK_FACTOR(0,n)

LoadFactor(n)

DL Level

6

0 for all neighbor cell

0

-100

0 for all neighbor cell

0

Time allowed:

15 minutes

© Alcatel 191



2.6 Handover Candidate Cell EvaluationTraining exercise (2/2)

> Emergency HO detected

1 Book-keeping list

Book-keeping list(14;3) (1;0) (8;7) (3;1)

2 Averaging measurement

Averaged measurements and PBGT(n)AV_RXLEV_PBGT_HO

AV_RXLEV_PBGT_HO

(14;3)

(1;0)

(8;7)

(3;1)

-100

-95

-96

-106

PBGT(n)

-2

3

2

-8

3 PBGT Filtering

PBGT(n)

(1;0)

(8;7)

3

2

PBGT Filtering

4 GRADE evaluation process

GRADE(n)

(1;0)

(8;7)

3

2

GRADE evaluation process

5 Target Cell

(1;0)

? ?

?

?

?

© Alcatel 192



2.7 Exercise





Handover Detection


Handover Management

Exercise

© Alcatel 193



2.8 Exercise

> List all the parameters involved in the detection of cause 23

> List all the causes impacted by the parameter DELTA_INC_HO_MARGIN

> List all the causes impacted by the parameter L_RXQUAL_UL_H

> List all the causes impacted by the parameter BS_TXPWR_MAX

> List all the causes impacted by the parameter BS_P_CON_ACK

Time allowed:

10 minutes

© Alcatel 194


3 OTHER ALGORITHMS

© Alcatel 195



3 OTHER ALGORITHMSSession presentation

> Objective: to be able to describe LCS, SDCCH Dynamic allocation, TCH resource allocation, MS reselection algorithms and list the associated parameters

> Program:

3.1 Dynamic SDCCH allocation

3.2 TCH resource allocation algorithm

3.3 MS Reselection algorithms

3.4 3G to 2G HO filtering algorithm



S3: OTHER ALGORITHMS


S5: CASE STUDIES

© Alcatel 196


3 OTHER ALGORITHMS






© Alcatel 197



3.1 Dynamic SDCCH allocationPurpose

> SDCCH/8 time slots can be dynamically allocated on demand on a cell-by-cell basis.

– “Dynamic SDCCH/8 time slots”.

– “Static SDCCH time slots”

Min

Max

Static SDCCHtimeslots

AllocatedDynamic SDCCH/8

timeslots

0

TCH Capacity

> Definitions

A Static SDCCH timeslot is a physical timeslot fixed allocated on the air interface. It contains 3, 4, 7 or 8 SDCCH sub-channels depending on whether the timeslot is an SDCCH/3, SDCCH/4, SDCCH/7, or SDCCH/8 timeslot.

© Alcatel 198



3.1 Dynamic SDCCH allocationPrinciple (1/2)

> Principles– Too few SDCCH time slots could result in high blocking rate on

SDCCH (Configuration 1)

– Too many SDCCH time slots could lead to a lack of TCH resources (Configuration 2)

SDCCHtime slots

TCH CAPACITY

SDCCHtime slots

TCH CapacityTCH Capacity

Configuration 1 Configuration 2

Low signaling capacity

More TCH capacity

High signaling capacity

Less TCH capacity

> Definition

An SDCCH is a logical SDCCH sub-channel mapped on a Static SDCCH timeslot or a Dynamic SDCCH/8 timeslot.

> Signaling load cases

Timeslot split between signaling and traffic channels depends on the network signaling load. The main cases are:

- Normal signaling load cells:

Rural area cells in center of Location Areas

(e.g. 1 SDCCH timeslot for a 3-TRX cell)

- High signaling load cells:

Urban or suburban area cells in the center of a Location Area

Rural area cells at the border of Location Areas

(e.g. 2 SDCCH time slots for a 3-TRX cell)

- Very high signaling load cells:

Urban or suburban area cells at the border of a Location Area

Cells with high SMS load (more than one SMS per call)

(e.g. 3 SDCCH time slots for a 3-TRX cell)

© Alcatel 199



3.1 Dynamic SDCCH allocationPrinciple (2/2)

> Allocation and de-allocation of Dynamic SDCCH/8 time slots

• An additional dynamic SDCCH/8 timeslot is allocated by the BSC if there is no SDCCH sub-channel free in the cell.

• A dynamic SDCCH/8 timeslot is de-allocated by the BSC after T_DYN_SDCCH_HOLD (10s) delay if all of its SDCCH sub-channels become free

BCC SDC TCH TCH

TCH TCH TCH TCH

TCH TCH TCH TCH

TCH TCH TCH TCH

TCH TCH TCH TCH TCH TCH TCH TCHCell

Allocation ofDynamic SDCCH/8

times slots

BCC SDC

SDD TCH

TCH TCH

BCC SDC

SDD TCH

SDD TCH

BCCSDCSDD

: BCCH: Static SDCCH: Dynamic SDCCH

> The location of the Dynamic SDCCH/8 time slots are fixed by O&M configuration.

>

© Alcatel 200



3.1 Dynamic SDCCH allocationTIMESLOT types

> NEW TIMESLOT TYPES :

– SDCCH

Pure SDCCH or “ static SDCCH “

– TCH

Pure TCH

– TCH/SDCCH

“ dynamic SDCCH”

– TCH/SPDCH

– MPDCH

>The OMC-R provides the BSC with the following O&M type of radio timeslots:

• Main BCCH timeslot (BCC): It is a timeslot carrying FCCH + SCH + BCCH + CCCH.

• Main combined BCCH timeslot (CBC): It is a timeslot carrying FCCH + SCH + BCCH + CCCH + SDCCH/4 + SACCH/4.

• Static SDCCH timeslot (SDC): It is a timeslot carrying SDCCH/8 + SACCH/8.

• Dynamic SDCCH/8 timeslot (SDD): It is a timeslot carrying TCH + SACCH or SDCCH/8 + SACCH/8

• TCH timeslot (TCH): It is a timeslot carrying TCH + SACCH or PDCH

>In RAM point of view, a radio timeslot can be defined as:

• Pure BCCH timeslot: The BCCH timeslot is the radio timeslot configured as BCC by O&M. Such a timeslot only carries common CS signalling.

• Pure SDCCH timeslot: A pure SDCCH timeslot is a timeslot configured as a CBC or SDC by O&M. Such a timeslot can carry SDCCH traffic.

• Pure TCH timeslot: A pure TCH timeslot is a timeslot configured as TCH by O&M. Such a timeslot only carries TCH traffic.

• TCH/SDCCH timeslot: A TCH/SDCCH timeslot is a timeslot configured as SDD by O&M. Such a timeslot is dynamically allocated as TCH or as SDCCH depending on the usage of the timeslot. It can carry TCH traffic or SDCCH traffic.

• TCH/SPDCH timeslot: A TCH/SPDCH timeslot is a timeslot configured as TCH by O&M. Such a timeslot is dynamically allocated as TCH or as SPDCH depending on the usage of the timeslot. It can carry TCH traffic or PS traffic.

• MPDCH timeslot: A MPDCH timeslot is a timeslot configured as TCH by O&M. Such a timeslot can only carry common PS signalling.

>A pure SDCCH timeslot can carry x SDCCH sub-channels where x equal to:

− 4 in case of combined CCCH and when CBCH is not configured on the timeslot,

− 7 in case of non-combined CCCH and when CBCH is configured on the timeslot,

− 3 in case of combined CCCH and when CBCH is configured on the timeslot,

− 8 for a normal SDCCH timeslot.

>When allocated as SDCCH, a TCH/SDCCH timeslot can carry up to 8 SDCCH sub-channels.

© Alcatel 201



3.1 Dynamic SDCCH allocationAllocation algorithm

SDCCH Request

SDCCH mapped on "TCU very high load state" removal

Are they any free SDCCH sub-channelamong Static SDCCH timeslots?

Selection of oneSDCCH sub-channel

Yes No

Are they any free SDCCH sub-channelamong Dynamic SDCCH/8 already allocated?

Selection oneSDCCH sub-channel

Yes

Are they any Dynamic SDCCH/8 timeslotsavailable and free in the cell?

No

Allocate one DynamicSDCCH/8 timeslot

Yes No

SDCCH Requestrejected!!!

Principle 1 : Preference is given to pure SDCCH timeslots

Principle 2 : Balance TCU processor load between different TCUs

in fact before entering in this algorithm ( see slide) the first step is :

Removal of all the SDCCH subchannels mapped on TCU in « Very High Overload » state

Principle 3 : FR TRX preference

© Alcatel 202



3.1 Dynamic SDCCH allocationSDCCH sub-channel selection

Pure SDCCH timeslots

TS with Maximum Free SDCCH sub-channels

TS with lowest TCU load

TS on FR TRX

TS with lowest index on TRX with lowest TRX_ID

TCH/SDCCH TS allocated as SDCCH

TCH/SDCCH allocated as TCH

Pure SDCCH timeslots TS with lowest TCU loadPure SDCCH timeslots


Pure SDCCH timeslots

TS with lowest index on TRX with lowest TRX_IDTS with lowest index on TRX with lowest TRX_IDTCH/SDCCH allocated as TCH

TS on FR TRX



TCH/SDCCH allocated as TCH TS with lowest index on TRX with lowest TRX_ID


TS with lowest TCU load

TCH/SDCCH allocated as TCH

Note that a SDCCH request can not access the timeslots reserved by NUM_TCH_EGNCY_HO. If all remaining TCH/SDCCH timeslots are reserved by NUM_TCH_EGNCY_HO, then the SDCCH request shall be rejected.

© Alcatel 203



3.1 Dynamic SDCCH allocationDe allocation algorithm

> CASE 1:

> IF all SDCCH sub-channels of a TCH/SDCCH timeslot become back freeTHEN the T_DYN_SDCCH_HOLD timer (10s, not tunable) is started.

> IF the timeslot is still free of SDCCH sub-channel when the timer expiresTHEN it is de-allocated (it becomes back TCH).

> CASE 2:

> IF several TCH/SDCCH timeslots are allocated as SDCCHAND IF all of them become free of SDCCH sub-channels when the timer runs

> THEN all these timeslots except one are de-allocated (become back TCH) without awaiting the timer expiration.(the last one waiting for the timer expiration)

The de-allocation algorithm ensures that :

· TCH/SDCCH timeslots are not allocated too fast to TCH after de-allocating them

TCH/SDCCH timeslots are not re-allocated too frequently to SDCCH

Note : · while T_DYN_SDCCH_HOLD is running:

¨ the dynamic SDCCH/8 timeslot marked as “HOLD” is still considered as allocated to SDCCH (and can not be allocated to TCH);

¨ If a subsequent dynamic SDCCH/8 timeslot (used as SDCCH and in the same cell) becomes free:

a) If this just freed dynamic SDCCH/8 timeslot has a higher priority, T_DYN_SDCCH_HOLD is re-started and precedent dynamic SDCCH/8 timeslot in “HOLD” state is de-allocated immediately;

b) If this just freed dynamic SDCCH/8 timeslot has lower priority, and T_DYN_SDCCH_HOLD is re-started and the just freed dynamic SDCCH/8 timeslot is de-allocated immediately.

© Alcatel 204



3.1 Dynamic SDCCH allocationO&M configuration 1/2

> Massive modification by script

• 10 templates

• Template customization

• Template launched through PRC

> Selection of static or dynamic SDCCH

• Timeslot configuration menu

BTS

BTS

BTS

BTS

2

4

7

3

1

10

9

6

12

8

5

11

>Dynamic sdcch rules

>The CBCH must be configured on a static SDCCH/8 or SDCCH/4 timeslot.

>Combined SDCCHs (SDCCH/4 + BCCH) are always static.

>To avoid incoherent allocation strategy between SDCCH and PDCH, a dynamic SDCCH/8 timeslot cannot have the characteristic of being a PDCH (it cannot carry GPRS traffic).

>The operator must configure at least one static SDCCH/8 or SDCCH/4 timeslot on BCCH TRX in a cell.

>In cells with E-GSM, only the TRX, which do not belong to the G1 band, can support dynamic and static SDCCHs.

>In multiband and concentric cells, only the TRX, which belongs to the outer zone, can support dynamic and static SDCCHs.

>Up to 24 static/dynamic SDCCH sub-channels can be configured per TRX.

© Alcatel 205



3.1 Dynamic SDCCH allocationO&M configuration 2/2

> Default configuration for a cell which has only Full rate TRX

Number of TRXin the cell

Number ofStatic SDCCH

Number ofDynamic SDCCH

Total numberof SDCCH

MaximumSDCCH/TRX

ratio

Is BCCH/CCCHcombined with

SDCCH?

1

2

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

4

4

8

8

8

8

8

16

16

16

16

16

16

16

24

24

24

8

8

16

16

24

24

24

24

24

32

32

32

40

40

40

48

48

12

12

24

24

32

32

32

40

40

48

48

48

56

56

64

72

72

12.0 (note 1)

6.0

12.0

8.0

8.0

6.4

5.3

5.7

5.0

5.3

4.8

4.4

4.7

4.3

4.6

4.8

4.5

Yes

Yes

No

No

No

No

No

No

No

No

No

No

No

No

No

No

No

Note1: For one TRX, dynamic SDCCHs are over-dimensioned because of the granularity of 8. According to the Alcatel traffic model, all dynamic SDCCHs will not be used.

Note2: An additional dynamic SDCCH/8 must be provided for each DR TRX (these are expected mainly on small cells).

> rules:

• At least one static SDCCH/4 or SDCCH/8 on BCCH TRX

– Up to 24 static/dynamic SDCCH sub-channels per TRX

– Up to 32 static/dynamic SDCCH sub-channels per TCU

– Up to 88 static/dynamic SDCCH sub-channels per CELL

© Alcatel 206


3 OTHER ALGORITHMS






© Alcatel 207



3.2 TCH resource allocation algorithmRadio Allocation and Management

> Radio resource allocation and management (RAM) aims at:

• Managing pools of TCH radio resources by:

– defining TCH radio timeslots as a function of the cell radio configuration from the operator

– sorting these TCH TS according to their radio capabilities (FR or DR, frequency band (G1 or GSM/DCS))

• Allocating dedicated TCH radio resources by:

– selecting the TCH pool in which the TCH should be chosen according to:

– the requested channel rate (FR or HR)

– the radio capability of the mobile

– the TRE DR capability and the TRE band

– selecting the best TCH resource among the available TCH channels of this pool according to several criteria

© Alcatel 208



3.2 TCH resource allocation algorithmRadio Timeslot of a cell : Operator view

> On the OMC-R the operator can configure the following Radio TS per cell:

• Main BCCH timeslot (BCC): TS carrying FCCH + SCH + BCCH + CCCH

• Main combined BCCH timeslot (CBC): TS carrying FCCH + SCH + BCCH + CCCH + SDCCH/4 + SACCH/4

• Static SDCCH timeslot (SDC): TS carrying SDCCH/8 + SACCH/8

• Dynamic SDCCH/8 timeslot (SDD): TS carrying TCH + SACCH or SDCCH/8 + SACCH/8

• TCH timeslot (TCH): TS carrying TCH + SACCH or used as a PS timeslot (PDCH)

> The operator has to choose between a Combined BCCH (CBC TS) or a Non-combined BCCH configuration (BCC TS).

> A PDCH is a radio timeslot used for PS traffic or signalling.

> It can carry either PS traffic or PS signalling but not both.

• If it carries traffic it is called a Slave PDCH (SPDCH) TS and it carries the logical channels PDTCH+PACCH+PTTCH.

• If it carries signalling it is called a Master PDCH (MPDCH) TS and it carries:

– either the logical channels PBCCH+PPCH+PAGCH+PRACH: it is then called a Primary MPDCH

– or only PPCH+PAGCH+PRACH: it is then called a Secondary MPDCH

> SDD TS can carry either TCH or SDCCH channels but not both at the same time.

> TCH TS can carry either CS traffic channel TCH or PS logical channels but not both at the same time.

© Alcatel 209



3.2 TCH resource allocation algorithmRadio Timeslot of a cell : RAM view

> In the BSS the RAM software module maps the OMC-R cell radio configuration to its own types of TS :

• Pure BCCH timeslot: BCC TS carrying only common CS signalling (BCCH+CCCH)

• Pure SDCCH timeslot: CBC or SDC TS carrying only dedicated CS signalling (SDCCH)

• Pure TCH timeslot: TCH TS carrying only TCH traffic

• TCH/SDCCH timeslot: SDD TS carrying either CS traffic (TCH) or dedicated CS signalling (SDCCH)

• TCH/SPDCH timeslot: TCH TS carrying either CS traffic (TCH) or PS traffic (SPDCH channels)

• MPDCH timeslot: TCH TS carrying common PS signalling (PBCCH+PCCCH or PCCCH only)

> TCH/SDCCH timeslots are allocated as TCH or SDCCH according to an SDCCH dynamic allocation algorithm presented in the “Introduction to Radio Fine Tuning B8” training course.

> TCH/SPDCH timeslots are allocated as TCH or SPDCH according to a SPDCH dynamic allocation algorithm presented in the “Introduction to GPRS & E-GPRS Quality of Service Monitoring B8” training course.

© Alcatel 210



3.2 TCH resource allocation algorithmRadio Timeslot : OMC-R / RAM mapping

> NB_TS_MPCH MPDCH TS are defined on the BCCH TRX :

• on the timeslots configured as TCH TS on the OMC-R

• having the lowest timeslot index

> TCH/SPDCH TS are defined as being part of an SPDCH group

> Pure TCH timeslots are OMC-R TCH TS neither defined as MPDCH TS nor in an SPDCH group

TCH

Pure BCCH

Pure SDCCH

TCH/SDCCH

TCH/SPDCH

MPDCH

Pure TCH

BCC

CBC

TCHSDC

SDD

TCH

OMC-Rradio TS

RAMradio TS

> MPDCH TS are defined on the BCCH TRX even if the corresponding TRX_PREF_MARK is different than 0.

© Alcatel 211



3.2 TCH resource allocation algorithmDefinition of a TCH/SPDCH TS

> For PS traffic resource allocation, an SPDCH group is defined on a per TRX basis and is made of consecutive timeslots:

• mapped on OMC-R TCH TS

• located on a PS capable TRX (TRX_PREF_MARK = 0)

• not defined as MPDCH TS

• having the same radio configuration (MA, MAIO)

> If several SPDCH groups can be defined on a given TRX, the BSS chooses the SPDCH group of timeslots having the highest number of consecutive timeslots.

> A radio timeslot belonging to one of the different SPDCH groups of the cell is identified in RAM as a TCH/SPDCH timeslot.

> The timeslots shall be consecutive on a given TRX means that there shall be no hole in the SPDCH group.

> If several SPDCH groups can be defined on the same TRX and having the same number of consecutive timeslots then the group that is located on the left side of the TRX (i.e. the timeslots having the lowest index) shall be chosen.

© Alcatel 212



3.2 TCH resource allocation algorithmExercise 1

> A non hopping cell is configured on the OMC-R

> Find the radio TS configuration in RAM if NB_TS_MPDCH= 2

TRX1

TRX2

TRX3

TRX4

0 1 2 3 4 5 6 7

MPDPBCPSDPTCTSDTSP

: MPDCH: Pure BCCH: Pure SDCCH: Pure TCH: TCH/SDCCH: TCH/SPDCH

BCC TCH SDC TCH

SDD TCH SDC TCH

TCH TCH TCH TCH

TCH TCH TCH TCH

TCH TCH TCH TCH TCH TCH TCH TCH


TRX1

TRX2

TRX3

TRX4

TRX_PREF_MARK

0

0

0

1

0 1 2 3 4 5 6 7

> The timeslots shall be consecutive on a given TRX means that there shall be no hole in the SPDCH group.

> If several SPDCH groups can be defined on the same TRX and having the same number of consecutive timeslots then the group that is located on the left side of the TRX (i.e. the timeslots having the lowest index) shall be chosen.

© Alcatel 213



3.2 TCH resource allocation algorithmTCH pools

> 3 pools of TCH resources are managed per cell:

• G1 pure TCH pool: contains all the free TCH sub-channels (FR or HR) free on the pure TCH TS of the G1 TRXs

• GSM/DCS pure TCH - TCH/SPDCH pool: contains all the free TCH sub-channels (FR or HR) free on the pure TCH TS and on the TCH/SPDCH TS of the GSM/DCS TRXs

• GSM/DCS TCH/SDCCH pool: contains all the free TCH sub-channels (FR or HR) free on the TCH/SDCCH TS of the GSM/DCS TRXs

> Any pure TCH, TCH/SPDCH, TCH/SDCCH TS can be:

• Busy: if it is not free to serve a FR TCH request

• Free: if it is free to serve a FR TCH request

> A DR TS (timeslot on a DR TRX) is free if no FR TCH or HR TCH is allocated for a call on this timeslot.

> A DR TS is busy if at least one TCH is allocated for a call on this timeslot:

• 1 FR TCH

• or 1 HR TCH (HR 0 TCH or HR 1 TCH)

• or 2 HR TCHs (HR 0 TCH and HR 1 TCH)

© Alcatel 214



3.2 TCH resource allocation algorithmTCH sub-pools

> FR TCH channels can be allocated on both FR and DR TRXs whereas HR TCH channels can only be allocated on DR TRXs

> Each of the three TCH pools is divided in three sub-pools:

• FR sub-pool: contains all the free FR TCH sub-channels available on the FR TRX

• DR: sub-pool: contains all the free FR TCH sub-channels available on the DR TRX

• HR sub-pool: contains all the free HR TCH sub-channels whose mate HR TCH sub-channel is busy(always located on the DR TRX)

> Inputs for TCH allocation function:

© Alcatel 215



3.2 TCH resource allocation algorithmTCH allocation process 1/2

TCH Request

TCH Allocation

- Radio capability of the mobile- Channel type (FR, HR, DR)- Speech version (FR, HR, EFR, AMR FR, AMR HR)- Request type (NA or HO)

- Cell channel type capability- Cell codec type capability- Cell load

TCH selected

TCH free?

Yes

Queuing?

Select a TCH sub-pool

Select a TCH in this sub-pool

TCH rejectedTCH queued

Yes No

No

Inputs for TCH allocation function:

> radio capability of the MS:

• the BSS knows the radio capability of the mobile from the MS CLASSMARK after the Radio Link Establishment procedure

> requirements from the MSC:

channel type (mandatory) is one of the following:

list of preferred speech version (optional):

– GSM full rate speech version 1 = FR

– GSM full rate speech version 2 = EFR

– GSM full rate speech version 3 = AMR FR

– GSM half rate speech version 1 = HR

– GSM half rate speech version 3 = AMR HR

> capabilities of the cell:

• FR TCHs only if only FR TRXs / FR+HR TCHs if some DR TRXs

• codec supported among: FR, EFR, AMR FR, HR, AMR HR

FR Full Rate only

HR Half Rate only

DR FR P NCA Dual Rate Full Rate Preferred No Changes Allowed after first channel allocationas a result of the request

DR FR P CA Dual Rate Full Rate Preferred Changes Allowed after first channel allocation as aresult of the request

DR HR P NCA Dual Rate Half Rate Preferred No Changes Allowed after first channel allocationas a result of the request

DR HR P CA Dual Rate Half Rate Preferred Changes Allowed after first channel allocation as aresult of the request

DR SV P NCA Dual Rate No Changes of channel rate Allowed after first channel allocation as aresult of the request

DR SV P CA Dual Rate Changes of channel rate Allowed after first channel allocation as aresult of the request

© Alcatel 216



3.2 TCH resource allocation algorithmTCH allocation process 2/2

TCH Allocation

TCH free?

Queuing?

TCH selected

Select a TCH sub-pool

Select a TCH in this sub-pool

TCH rejectedTCH queued

Yes No

Yes No

ALLOC_ANYWAYT11T11_FORCEDT_QHO

NUM_TCH_EGNCY_HO

- The timer T11 corresponds to normal assignment with queuing authorised.

- The timer T11_FORCED corresponds to normal assignment

i) when the queuing is not authorised by the MSC but forced by the BSC (QUEUE_ANYWAY = TRUE),

or ii) when the queuing is not authorised but the request has its pre-emption indicator set and has already forced the release of a lower priority pre-emptable on-going call.

The QUEUE_ANYWAY flag is checked by the Normal Assignment (NASS) entity.

- The timer T_qho corresponds to an external channel change with queuing authorised or to an external channel change when the queuing is not authorised but the request has its pre-emption indicator set and has already forced the release of a lower priority pre-emptable on-going call.

© Alcatel 217



3.2 TCH resource allocation algorithmTCH sub-pool selection

> The BSS selects the TCH sub-pools in which a TCH channel can be allocated according to:

• The requested channel rate and the cell load situation

– favour HR if cell is loaded

• A priority given to generic resources

1. G1 pool (E-GSM mobile only)

2. GSM/DCS pure TCH - TCH/SPDCH pool

3. GSM/DCS TCH/SDCCH pool

• An optimisation of FR/HR resources

– favour FR pool over DR pool for a FR TCH request

– favour HR pool over DR pool for an HR TCH request

• The availability of a TCH channel in the sub-pool

> TCH allocation without list of preferred speech versions

• FR request: FR pool � DR pool

• HR request: HR pool � DR pool

• DR FR Preferred request:

– cell load=False: FR pool � DR pool � HR pool

– cell load=True: HR pool � DR pool � FR pool

• DR HR Pref. request: HR pool � DR pool � FR pool

> TCH allocation with a list of preferred speech versions

• FR SV then HR SV: FR pool � DR pool � HR

• HR SV then FR SV: HR pool � DR pool � FR

• FR SV only: FR pool � DR pool

• HR SV only: HR pool � DR pool

> favour G1 pool for an E-GSM mobile (penetration of E-GSM mobile is low and GSM/DCS traffic is high)

> disfavour TCH allocation on TCH/SDCCH TS (favour signalling over traffic)

> Example : E-GSM mobile / DR FR P NCA / no sub-pool is empty

– BSS selects a TCH in the G1 pure TCH pool / FR sub-pool

© Alcatel 218



3.2 TCH resource allocation algorithmTCH selection

> Sub-pool of the GSM/DCS pure TCH - TCH/SPDCH pool

• Optimise CS/PS traffic resources

1. Favour TCH allocation on pure TCH TS

2. Optimise PS traffic on TCH/SPDCH TS

– TCH allocated on TRX of highest TRX rank

» and on TS of highest TS index

– SPDCH allocated on TRX of lowest TRX rank

» and on TS of lowest TS index

> 2 modes of TCH selection

• On pure TCH or TCH/SDCCH timeslots

• On TCH/SPDCH timeslots

> TCH selection on pure TCH or TCH/SDCCH timeslots if:

• there is at least one candidate TCH free on pure TCH TS

OR

• there is no candidate TCH free on TCH/SPDCH TS

– only the candidate TCH sub-channels available on pure TCH TS and on TCH/SDCCH TS are kept as candidate

> TCH selection on TCH/SPDCH timeslots if:

• there is at least one candidate TCH free on a TCH/SPDCH TS

AND

• there is no candidate TCH free on pure TCH TS

– only the candidate TCH sub-channels available on TCH/SPDCH TS are kept as candidate

© Alcatel 219



3.2 TCH resource allocation algorithmTCH selection on pure TCH or TCH/SDCCH TS

> The TCH is chosen from the selected sub-pool according to the following criteria:

Non hopping cellBiggest Mobile AllocationEN_MA_SELECTION = true

TCH selected

Highest TS index

HR 0 TCH sub-channel

TCH candidates of the selectedTCH sub-pool

Highest TRX_PREF_MARK

FR allocation orHR allocation on busy TS

Best Interference Band

Highest TRX identity

> The BSS attempts to offer the best quality of service for TCH calls in accordance with the privileged order between the groups of TRXs (if any) defined by the operator. Among a group of TRXs the BSS attempts to allocate traffic channels that have the best quality characteristics (channels using frequency with low reuse factor, large hopping frequency sets, low measured interference).

> The benefits from this type of allocation are that the operator has the possibility to define groups of TRXs and to favour (or to disadvantage) them on the other if he wants to do so. Among a group of pure TCH or TCH/SDCCH timeslots, the overall interference is kept as low as possible, thus the user will perceive a better quality of service.

> The BSS chooses the best TCH among the sub-channels of the selected TCH sub-pool applying criteria below in the specified order of priority:

1. TCH on TS with the highest TRX Preference Mark

– According to the frequency plan, the coverage and interference probability of a cell (or according to measurements), the operator may know which TRX should be a priori favored for TCH selection. For that purpose, it is possible for operators to give a preference mark to each TRX of a cell. This mark is given through the parameters TRX_PREF_MARK (TPM) changeable at OMC-R side per TRX. The range of TRX_PREF_MARK will be from 0 (lowest priority) to 7 (highest priority). The TCH selection function favours the channels with the highest TPM.

– Note that a few Pure TCH TS should be available in a cell on a TRX of TRX_PREF_MARK value of 0 since TCH/SPDCH TS may also be defined on this TRX according to PS radio resource configuration.

2. TCH on TS with the biggest Mobile Allocation (for hopping cell only)

– Considering that the number of frequencies is a key factor for the average quality of channels, the TCH selection function favors the TS with the biggest MA (i.e. with the most frequencies in their frequency hopping sequence). This selection criterion is enabled/disabled via the flag EN_MA_SELECTION changeable at the OMC-R side on a per cell basis.

3. TCH on TS from the best Interference Band

– Considering that the uplink received level measured by the BTS on an idle channel is a means to assess the quality when in connected mode, the TCH selection function favours the TS belonging to the best Interference Band (IB). Five IBs are defined through 5 parameters INTFBD1 to INTFBD5 where INTFBD(i)< INTFBD(i+1) and INTFBD5 = -47 all changeable at the OMC-R side on a per BTS basis.

4. TCH on TRX with the highest TRX identity

5. TCH on TS with the highest TS index

6. HR 0 TCH if the two sub-channels remaining candidates are the 2 HR TCH of the same free TS

© Alcatel 220



3.2 TCH resource allocation algorithmTCH selection on TCH/SPDCH TS

> The TCH is chosen from the selected sub-pool according to the following criteria:

• TRX rank is determined by the TRX Ranking algorithm described inthe “GPRS & EGPRS Radio Algorithms Description” training course

TCH selected

Highest TS index

HR 0 TCH sub-channelFR allocation or

HR allocation on busy TS

Highest TRX identity

TCH candidates of the selectedTCH sub-pool

> The BSS tends to allocate to the MFS the TCH/SPDCH timeslots so as to avoid conflicts between CS and PS allocations on PS capable TRX.

> In order to be able to allocate as much slave PDCHs as possible to a given TBF, it is important to avoid any mix of allocation between TCHs and SPDCHs (e.g. avoid on a TRX a configuration such as TCH – TCH – SPDCH – SPDCH – TCH – SPDCH –SPDCH – SPDCH). For that purpose, a TRX rank is assigned to each PS capable TRX. The TRX having the highest TRX rank is preferentially selected for TCH allocations, whereas TRX having the lowest TRX rank is preferentially selected for SPDCH allocations

> This rule only applies on PS capable TRX. On a given PS capable TRX, TCH are preferentially allocated on the right side of the TRX (highest TS index), whereas SPDCH are preferentially allocated on the left side (lowest TS index).

© Alcatel 221



3.2 TCH resource allocation algorithmExercise 2 - 1/3

> A cell is configured on the OMC-R and TRE are mapped by BSS

Time allowed:

10 minutes

BCC SDC TCH TCH

SDD TCH TCH TCH

TCH TCH TCH TCH

TCH TCH TCH TCH

SDC TCH TCH TCH TCH TCH TCH TCH


TRX1

TRX2

TRX3

TRX4

TRX_PREF_MARK

0

0

1

0

0 1 2 3 4 5 6 7

TCH TCH TCH TCH TCH TCH TCH TCHTRX51

TRE

G4 MP FR

G4 MP DR

G3 DR

G4 MP FR

G3 DR

© Alcatel 222




> Find the radio TS configuration in RAM if NB_TS_MPDCH= 2

MPD MPDCH

PBC Pure BCCH TS

PSD Pure SDCCH TS

PTC Pure TCH TS

TSD TCH/SDDCH TS

TSP TCH/SPDCH TS

TRX1

TRX2

TRX3

TRX4

TRX_PREF_MARK

0

0

1

0

0 1 2 3 4 5 6 7

TRX51

TRE

G4 MP FR

G4 MP DR

G3 DR

G4 MP FR

G3 DR

© Alcatel 223




> Find which TCH sub-channel is allocated:

1. For MS1: E-GSM, DR

2. For MS2: GSM/DCS, DR

3. For MS3: GSM, FR

4. For MS4, MS5, …., MSn: E-GSM, DR

n = ?

Pure TCH TS

TCH/SPDCH TS

TCH/SDDCH TSas TCH TS

FHP

Cell load = true

: FR TCH call: HR TCH call: SPDCH TS

TSD P P P

P P P

P F

F F F F F F

P P P P P P P

TRX1

TRX2

TRX3

TRX4

TRX_Rank

2

3

-

1

0 1 2 3 4 5 6 7

F FTRX5-

TRE

GSM/FR

GSM/DR

GSM/DR

GSM/FR

G1/DR

H

H HHHHHH

© Alcatel 224


3 OTHER ALGORITHMS






© Alcatel 225



> At startup (IMSI Attach), the MS is selecting a cell with

• best C1

• once “camped on” one cell (in idle mode)…

> …the MS can decide to reselect on another one if:

• C1 criteria is too low

• the MS cannot decode downlink messages

• the current cell is becoming forbidden (e.g. barred)

• the MS cannot access the cell

• there is a better cell, regarding C2 criteria

3.3 MS Reselection algorithmsSelection and reselection principles

> Idle mode

• Status null:the mobile station (MS) is off

• Status search BCCH:the MS searches a broadcast channel with the best signal level (cell selection and reselection)

– BCCH list: up to 36 BCCH frequencies plus BSIC can be saved on SIM per visited network.

– Look if frequencies of the BCCH list can be used.

– No entries in the BCCH list, or the location is completely different: scan frequency band.

• Status BCCH:the MS is synchronized on a BCCH. The MS camps on a cell.

– The BTS sends the neighbor cells list (BCCH allocation BA) on BCCH in System Information (SI) 2, 2bis and 2ter if BSS parameter EN_INTERBAND_NEIGH in dual band networks:

– GSM900 serving cell

» GSM900 neighbor cells put into SI 2

» GSM1800 neighbor cells put into SI 2ter/2bis

– GSM1800 serving cell

» GSM900 neighbor cells put into SI 2ter

» GSM1800 neighbor cells put into SI 2/2bis

– The MS measures RXLEV from BCCH of the serving and neighbor cells.

– Camping on a cell is performed using C1 criteria only (the chosen cell is the one with the best C1)

– The MS needs to have access to the network.

– The MS needs to be accessible by the network.

– Reselection is done using the mechanisms referenced above

– ‘handover algorithms’ in idle mode

© Alcatel 226



> C1

• ensure that, if a call was attempted, it would be done with a sufficient downlink and uplink received level

• based on 2 parameters, broadcast on BCCH

– RXLEV_ACCESS_MIN [dBm]

– minimum level to access the cell

– MS_TXPWR_MAX_CCH [dBm]

– maximum level for MS emitting

3.3 MS Reselection algorithmsC1 criteria (1/2)

© Alcatel 227



> C1

• evaluated every 5 sec (minimum)

• C1 = A - MAX(0,B) > 0

• A = RxLev - RXLEV_ACCESS_MIN

– assess that the MS received level is sufficient

• B = MS_TXPWR_MAX_CCH - P

– P maximum power of MS

– assess that the BTS received level will be sufficient

– if MS_TXPWR_MAX_CCH < P

• If A > 0 & B < 0 OK, if B > 0, it can be compensated by A

– A >> 0 means that the MS is closer to the BTS

3.3 MS Reselection algorithmsC1 criteria (2/2)

© Alcatel 228



> C2

• CELL_RESELECT_PARAM_IND= not present THEN C2=C1 else

– C2 = C1 + CELL_RESELECT_OFFSET - TEMPORARY_OFFSET (T) (if PENALTY_TIME ≠ 31)

– if T > PENALTY_TIME, TEMPORARY_OFFSET(T) = 0

– used to avoid locating on “transient cell”

– CELL_RESELECT_OFFSET used to favor cell among other (e.g. micro-cell vs. umbrella, once T > PENALTY_TIME)

– Or C2 = C1 - CELL_RESELECT_OFFSET (if PENALTY_TIME = 31)

– CELL_RESELECT_OFFSET used to handicap some cells among others

• One reselection criterion is compared to C2s

– C2neighbor > C2current if cells belong to same LA

– C2neighbor > C2current+Cell_Reselect_Hysteresis if cells from a different LA

3.3 MS Reselection algorithmsC2 criteria

> Note:

• CRO: from 0 to 126 dB, step 2dB

• PENALTY_TIME: from 0=20s to 30=620s, step: 20s; 31=infinite

• TEMPORARY_OFFSET: from 1=10dB to 6=60dB; 7 = infinite

> The use of a second formula (Penalty_time = 31) is restricted to very special cases, as we do not like to penalize a cell. If a cell is parametered with PT=31, it will be penalized compared to ALL its neighbors. To penalize a cell compared to one neighbor, one should better boost the neighbor cell (using the first formula).

> The first formula is very useful for favoring indoor cell or microcell.

> Cell selection and cell reselection considering CELL_BAR_QUALIFY

• in case of phase 2 MS and CELL_RESELECT_PARAM_IND=1, it is possible to set priorities to cells

• CELL_BAR_QUALIFY

– Two values:

– 0 = normal priority (default value)

– 1 = lower priority

– Interacts with CELL_BAR_ACCESS (barring cell)

• A phase 2 MS selects the suitable cell with the highest C2 (C1>0) belonging to the list of normal priority.

• If no cell with normal priority is available then the MS would select the lower priority cell with the highest C2 (C1>0).

© Alcatel 229



3.3 MS Reselection algorithmsTraining Exercise (1/2)

> On this network example

• List the parameters involved in the selection / reselection process

Time allowed:

5 minutes Cell

Sectorized cell

CI=6169GSM900

Concentric cell

(8564, 1964)

(8564, 6169)

(8557, 1823)

Cell

CI=6271GSM900

CI=6270, GSM900

CI=1823GSM900

CI=1964GSM900

© Alcatel 230



3.3 MS Reselection algorithmsTraining Exercise (2/2)

Cell 1

Cell 2

CI=6169GSM900

Cell 3

(8564, 1964)

(8564, 6169)

(8557, 1823)

Cell

CI=6271GSM900

CI=6270, GSM900

CI=1823

GSM900

CI=1964GSM900

• Find the selected cell by the MSMeasurements RxLev (cell 1) RxLev (cell 2) RxLev (cell 3)

1

2

3

4

5

-80

-84

-88

-88

-89

-96

-90

-90

-87

-85

-104

-100

-87

-82

-78

© Alcatel 231


3 OTHER ALGORITHMS


B9





© Alcatel 232



> From B7, the 3G to 2G Handovers are managed as incoming HO in BSS but :

• What was the weakness ?

• How to improve it ?

• What do we have to compute ?

• What is necessary to implement ?

3.4 3G to 2G HO filtering algorithmPurpose

B9

© Alcatel 233



> In case of 2G cell overloaded we had no way to reject the 3G HO, so 2G cells can be congested because 3G network is under lack of coverage.

> We must have the possibility to reject 3G incoming HOs in case of 2G target cell is loaded.

> We have first to compute periodically the load of our 2G cells.

> Then, to compare it with a specific parameter we have to create in order to decide the need of rejection.

3.4 3G to 2G HO filtering algorithmProblem and solution

B9

© Alcatel 234



> The traffic load computation is the long term one, already used for HO causes 12 and 23.

> The result is compared with THR_CELL_LOAD_3G_REJECT in order to evaluate “3G_HOReject_Load State”

• IF the last N_TRAFFIC_LOAD AV_TRAFFIC_LOAD ≥THR_CELL_LOAD_3G_REJECT

– THEN 3G_HOReject_Load State = HIGH

• ELSE IF the last N_TRAFFIC_LOAD AV_TRAFFIC_LOAD < THR_CELL_LOAD_3G_REJECT

– THEN 3G_HOReject_Load State = LOW

3.4 3G to 2G HO filtering algorithmalgorithms and parameters involved (Evaluation) 1/3

B9

Example:

IF

N_TRAFFIC_LOAD = 6

A_TRAFFIC_LOAD = 4

As TCH_INFO_PERIOD is fixed to 5s

The Traffic evaluation AV_TRAFFIC_LOAD is revalued every 20 s ( 4 X 5s = 20s )

The Long Term decision is taken after N_TRAFFIC_LOAD times in the same state ( 2 mn in this example)

Time

AV_TRAFFIC_LOAD

THR_CELL_LOAD_3G_REJECT

3G_HOReject_Load_State

Time

Time

HIGH

LOW

6 High6 Low

6 HighTCH_INFO_PERIOD X A_TRAFFIC_LOAD

2 mn

© Alcatel 235



> IF the 3G to 2G handover is triggered by cause different from anemergency cause

– THEN IF 3G_HOReject_Load State = High

– Then the BSC shall enter the Hand over Failure Signalling procedure

– ElSE IF 3G_HOReject_Load State = Low

– Then the BSC shall accept the incoming handover

> IF the 3G to 2G handover is triggered by emergency cause

– Then the BSC shall accept the incoming handover

3.4 3G to 2G HO filtering algorithmalgorithms and parameters involved (Decision) 2/3

B9

© Alcatel 236



> In case of rejection, the BSC shall send an HO Failure message with:

• Cause indicating “no Radio resource available”

• Cell Load Information:

– Cell Capacity Class

– Cell Capacity Class = CELL_CAPACITY_CLASS

– Cell Load

– Cell Load = AV_TRAFFIC_LOAD * 100(With the last computed value of AV_TRAFFIC_LOAD)

> These information will be used by the RNC and its own algorithms in order to evaluate the necessity to retry the HO or not on the same cell.

3.4 3G to 2G HO filtering algorithmalgorithms and parameters involved (Rejection) 3/3

B9

The Cell Capacity Class should follow the recommended rule:

“In order to fulfill the 3GPP requirement of having a linear scale in the capacity class, ranging from 1 to

100:

Cell Capacity Class is a linear function of the Cell capacity: value 1 shall indicate the minimum capacity

class, and 100 shall indicate the maximum capacity class. Capacity class should be measured on a

linear scale.

The default value of Cell Capacity Class depends on the number of available TCHs in the cell and since

there may be up to 126 TCH channels in one GSM cell ( [ 8 TS X 16 TRX ] – 1 BCCH - 1 SDCCH ) :

Cell_Capacity_Class = INT ( ( 99 * ( NTCH – 1 ) / 125 ) +1 )

© Alcatel 237



3.4 3G to 2G HO filtering algorithmTraining Exercise

> Which Mobiles are rejected ?

> What is the Cell_Capacity_Class for each case ?

• THR_CELL_LOAD_3G_REJECT = 75 %

Time allowed:

10 minutes

MS

1

4

3

2

5

HO Cause

COMFORT

EMERG

COMFORT

EMERG

COMFORT

FREE TCH

3

3

2

0

12

N_TRAFFIC_LOAD

AV_TRAFFIC_LOAD

60

80

75

100

85

REJECTED

Cell

Capacity

Class

B9

© Alcatel 238


4 ALGORITHMS DYNAMIC BEHAVIOR

© Alcatel 239



4 ALGORITHMS DYNAMIC BEHAVIOR Session presentation

> Objective: to be able to Estimate qualitatively the impact of parameters change

> Program:


4.2 Examples and exercises





S5: CASE STUDIES

© Alcatel 240





Examples and Exercises

© Alcatel 241



4.1 Theoretical presentationSession objectives

> SESSION OBJECTIVES

• Be able to estimate qualitatively the impact of a parameter change

> JUSTIFICATION

• Tuning is not an exact science

• The optimizer has to control every parameter change and predict qualitatively what the consequences will be

• Note: Each change of parameter and its justification have to beregistered in a database for operation convenience

> DETAILED PROGRAM

• Three Example/Exercises

© Alcatel 242



4.1 Examples and Exercises


Examples and Exercises

© Alcatel 243



4.2 Examples and ExercisesOverview

> Example 1: Optimization of handover algorithms

• Sliding averaging window

> Example 2: Optimization of power control algorithms

• Sliding averaging window

> Example 3: Traffic load sharing

• Parameters qualitative influence

© Alcatel 244



> Search for best tuning of HO parameters to decrease call drop

4.2 Examples and ExercisesExample 1: Optimization of Handover Algorithms (1/4)

Call drop

HO/Call

© Alcatel 245



> Main Objective: make the HO algorithm as efficient as possible

• Minimize call drop rate

– trigger HO soon enough

– toward the “best” neighbor

• while keeping a good speech quality

– avoid HO due to quality: “too late”

– avoid having HO/call rate too high


© Alcatel 246



> Method

• Collect Abis trace chart

• Search for HO level to avoid quality lower than 4 (or even 3)

– sufficient number of “bad quality” samples

– low standard deviation

– problem when HO already activated

< R x Q u a l _ D L > = f ( A V _ R x L e v_ D L )

0

1

2

3

4

5

6

7

N b _ s a m p l e s

0

20 0

40 0

60 0

S t a n d a r d D e v i a t i o n

0

0 .5

1

1 .5

2

< R x Q u a l _ U L > = f (A V _ R x L e v_ U L )

0

1

2

3

4

5

6

7

N b _ s a m p l e s

0

20 0

40 0

60 0

80 0

1 00 0

S t a n d a r d D e v i a t i o n

0

1

2

3

> Then tune according to QoS indicators (OMC-R) by repetitive process

• A_PBGT_HO/A_LEV_HO/A_QUAL_HO

• L_RXLEV_UL_H, L_RXLEV_DL_H, L_RXLEV_UL_P, L_RXLEV_DL_P

• OK as soon as HO success rate stabilized


> Never forget that Abis information takes into account the traffic distribution in the cell. Any parameter tuning done after an Abisstudy has to be checked periodically as the distribution in the cell can change from one week to another.

> Use the pivot table function (Excel) to build this graph.

RxQUAL

0

1

2

3

4

5

6

7

-110-108-106-104-102-100 -9

8-96-94-92-90-88-86-84-82-80-78-76-74-72-70-68-66-64-62-60-58-56-54-52-50-48

RxQUAL

© Alcatel 247



> Neighboring relationship cleanup

• Remove useless relationships (A interface statistics, PM Type 180)

• Remove the common BCCH/BSIC couple

• Add new relationships when a new site is created

> Finally, check the main QoS indicators

• Call drop rate

• HO failure rate

• HO/call rate

• Radio Link Failure rate(the strong rate of radio link failure can denounce a lack of vicinity relation between cells)


© Alcatel 248



> According to the Abis results and some parametersalready set, tune qualitatively the sliding averaging windows:

– A_QUAL_HO

– A_LEV_HO

4.2 Examples and ExercisesExample 1: training exercise

Time allowed:

5 minutes

Level at RxQual=3 - 80 dBm - 96 dBm - 90 dBm

L_RXLEV_DL_H

A_QUAL_HO

A_LEV_HO

- 85 dBm

6

?

- 90 dBm

6

?

- 90 dBm

?

4

© Alcatel 249



> Optimization of Downlink Power Control

– Decrease of downlink interference

– Risks of delay of HO (without fast power control)

> Optimization of Uplink Power Control

– Decrease of Uplink interference

– MS battery saving

– Risks of delay of HO (without fast power control)

4.2 Examples and ExercisesExample 2: Power Control Algorithms Optimization (1/2)

© Alcatel 250



> The main tuning problem is the interaction with handover, which can slow down HO decision, and debase call drop rate

• Power control threshold must be within HO ones

• Dynamic step size must be activated if possible

4.2 Examples and ExercisesExample 2: Power Control Algorithms Optimization (2/2)

> In the example below, a dynamic MS PC is activated. The MS power changes are really reactive and control the UL level between -80 and -90dBm. In this example, the HO threshold is -98 dBm.

RxLev_UL

-100

-95

-90

-85

-80

-75

-70

1 39 77 115 153 191 229 267 305 343 381 419 457 495 533 571 609 647 685 723 761 799 837 875 913 951 989 1027

RxLev_UL

13

15

17

19

21

23

25

27

29

31

33

1 40 79 118 157 196 235 274 313 352 391 430 469 508 547 586 625 664 703 742 781 820 859 898 937 976 1015

MS_PwrLevel

© Alcatel 251



> Explain qualitatively the impacts of some parameter changes

– What happens if:»we increase POW_INC_FACTOR?

»we increase MAX_POW_INC?

»We increase A_LEV_PC?

4.2 Examples and ExercisesExample 2: Training Exercise

Time allowed:

5 minutes

© Alcatel 252



> Used to unload cell with too high traffic, without HW extension

> Trade-off between traffic sharing/radio quality

> Different algorithm

– Fast Traffic Handover: Cause 28

– Traffic Handover: Cause 23 and 12 with

DELTA_HO_MARGIN(0,n)

– Static (couple of cells): HO_MARGIN, LINK_FACTOR

– On a local traffic basis:

– Load_Factor/Free_Factor

– Forced Directed Retry

4.2 Examples and ExercisesExample 3: Traffic Load Sharing (1/12)

© Alcatel 253




> Fast Traffic HO

• Useful in case of sudden traffic peaks as the process response is instantaneous (no averaging window)

• The principle is to force handover towards neighbor cells which have lower traffic when a request is queued in the serving cell.

• Interaction with Forced DR due to the use of same thresholds

• Optimization method (repetitive process)

– Tunes L_RXLEV_NCELL_DR(n), FREElevel_DR(n)

– Applies new values, checks traffic peaks, QoS indicators

© Alcatel 254




> The Pros and cons of Fast Traffic HO

• Efficiency depends on

– Traffic location in the loaded cell

– Capacity of neighbor cells

Increase of the number of HO/call

Increase of incoming HOs fail rate (risk of ping-pong effect)

– In case of internal HO: use PING_PONG_HCP with T_HCP

or/and enable HO CAUSE 23

Heavy to tune (has to be done for each couple of cells)

Adapted to instantaneous traffic modification

Can be used to send traffic towards a cell external to the serving BSC

Adapted to hierarchical network, but also to standard ones

© Alcatel 255



> DELTA_HO_MARGIN (0,n)

> CHANGE DYNAMICALLY TRAFFIC DISTRIBUTION WITH HO:

• Traffic HO Cause 23

– Ease outgoing better condition HO on a traffic point of view

• Slow down outgoing better cell HO (to be tuned for a given couple of cells)

– When the better cell in radio condition is the worst cell in traffic terms


– Tune DELTA_DEC_HO_MARGIN and DELTA_INC_HO_MARGIN

– Apply new values, check traffic, QoS indicators and possibly speech quality


© Alcatel 256




> The Pros and cons of DELTA_HO_MARGIN (0,n) method

• Efficiency depends on

– Traffic location in the loaded cell

– Cells overlap


Increase the number of HO/call

Cannot be used to send traffic toward a cell external to the serving BSC

The call has to be first established on a loaded cell, before being “exported”

– It can be rejected

Easy to tune (dynamic process)

Adaptability to instantaneous and long term traffic modifications

© Alcatel 257



> HO_MARGIN / LINK_FACTOR

> CHANGE STATICALLY TRAFFIC DISTRIBUTION WITH HO:

• Ease outgoing better cell HO (to be tuned for a given couple of cells)

– Decrease HO_MARGIN (can make a cell “candidate”)

– Increase LINK_FACTOR (used to rank candidate cells)


– Look for neighbor cells able to carry extra traffic

– Use Abis trace to check if these cells are candidate

– if yes, use LINK_FACTOR to favor them

– if not, use HO_MARGIN and LINK_FACTOR

– Apply new values, check traffic, QoS indicators and possibly speech quality


© Alcatel 258




> The Pros and cons of LINK_FACTOR/HO_MARGIN

• Can be efficient (up to 20% increase of capacity) in some cases

– Cell overlap


Increase the number of HO/call

The call has to be first established on a loaded cell, before being “exported”

– It can be rejected

Heavy to tune (has to be done for each couple of cells)

No adaptability to instantaneous and long term traffic modifications

Can be used to send traffic toward a cell external to the serving BSC

© Alcatel 259



> FREE_FACTOR/LOAD_FACTOR

> Taking into account the current load of cells, send the MS toward the less loaded cell with HO

• Ease outgoing better cell HO, according to

– Load_Factor (% of TCH occupancy) of serving and “target”cells

– Free_Factor (number of free TCHs) of serving and target cells (order only)

– cannot make a “candidate” cell, only change ranking

• Tuning method (repetitive)

– to be activated locally for each cell with default parameter setting

– look for QoS indicators (esp. traffic intensity and blocking rate)

– tune tables accordingly


© Alcatel 260




> The Pros and cons of load/free factors method

Lower efficiency compared to LINK_FACTOR/HO_MARGIN

Calls have to be established on a loaded cell before being “exported”

Tuning is performed on a cell-per-cell basis

Cannot be used to send traffic toward an external cell

Adapted to dynamic change of traffic and capacity (for Load_Factor)No increase of HO/call rate

© Alcatel 261



> Forced directed retry method

• Mechanisms

– The MS is connected on an SDCCH of cell1

– It must switch on TCH

– No TCH is free on cell1

– There is at least 1 neighbor cell which has

– sufficient DL level seen by the MS

– enough free TCHs

– The MS is handed over to TCH towards this cell

– if there are several cells, the one with the best PBGT is selected


© Alcatel 262



> Method: trade-off between traffic and radio quality

• Mainly L_RXLEV_NCELL_DR(n)parameter to tune

– the lower, the better the traffic sharing

– the lower, the higher the interference risks

• QoS indicators and field tests (speech quality) are necessary for tuning


C

ell 2: 45

Cell 3: 23

Cell 1: 2

4

> Forced directed retry

• The following condition is checked every measurement reporting period and if at least one input pre-processed parameter AV_RXLEV_NCELL_DR(n) is available.

– CAUSE = 20 (high level in neighbor cell for forced directed retry)

– AV_RXLEV_NCELL_DR(n) > L_RXLEV_NCELL_DR(n) (n = 1 ... BTSnum)

– and EN_FORCED_DR = ENABLE

• The threshold L_RXLEV_NCELL_DR(n) is the observed level from the neighbor cell n at the border of the area where forced directed retry is enabled. This threshold fixes the size of the overlapping area where forced directed retry can be performed. It should be greater than RXLEVmin(n).

© Alcatel 263




> The Pros and cons of Forced directed retry

Highest efficiency (up to 30%)

No increase of HO/call rate

Can be used to send traffic toward an external cell

Adapted to dynamic change of traffic

Adapted to hierarchical networks, but also to standard ones

Tuning is performed on a cell-per-cell basis

© Alcatel 264



> Draw qualitatively the new serving areas on the pseudo map when enabling traffic HO with:

– DELTA_DEC_HO_MARGIN=6dB

– DELTA_INC_HO_MARGIN=4dB

4.2 Examples and ExercisesExample 3: training exercise (1/3)

Time allowed: 5 minutes

PBGT(0) = 5

05 5

PBGT(0) PBGT(n)

PBGT(n) = 5

Traffic_load

Loaded cell 0 Unloaded cell n

EN_TRAFFIC_HO = 0

Cause 12Cause 12

© Alcatel 265




> What happens when EN_FAST_TRAFFIC_HO = ENABLE and EN_TRAFFIC_HO(0,n) = DISABLE


QueuedAssignment Request

PBGT(0) = 5

05 5

PBGT(0) PBGT(n)

PBGT(n) = 5

Traffic_load


Av_Rxlev_Ncell(n) = -82 dBm Av_Rxlev_Ncell(0) = -74 dBmAv_Rxlev_PBGT_HO = -82 dBm

L_RLEV_NCELL_DR(n) = -85 dBm

© Alcatel 266




> What happens when EN_FAST_TRAFFIC_HO = ENABLE and EN_TRAFFIC_HO(0,n) = ENABLE

QueuedAssignment Request

PBGT(0) = 9

09 -1

PBGT(0) PBGT(n)

PBGT(n) = -1

Traffic_load


Av_Rxlev_Ncell(n) = -82 dBm Av_Rxlev_Ncell(0) = -74 dBmAv_Rxlev_PBGT_HO = -82 dBm

5 5


© Alcatel 267


5 CASE STUDIES

© Alcatel 268



5 CASE STUDIES Session presentation

> Objective: to be able to propose a set of parameters to solve typical radio problems

> Program:


5.2 TUNNEL Case

5.3 RADAR Case

5.4 TOWER Case

5.5 RESURGENCE Case

5.6 FOREST Case

5.7 HIGHWAY Case

5.8 TCH/SDCCH CONGESTION Case

5.9 INDOOR CELL CONGESTION Case





S5: CASE STUDIES

© Alcatel 269


5 CASE STUDIES



TUNNEL Case

RADAR Case

TOWER Case

RESURGENCE Case

FOREST Case

HIGHWAY Case

TCH/SDCCH CONGESTION Case

INDOOR CELL CONGESTION Case

© Alcatel 270



> SESSION OBJECTIVES

– Be able to propose an appropriate set of parameters

to solve typical field problems

> JUSTIFICATION

– Some typical problems due to particular field

configuration always occur in a GSM network

> DETAILED PROGRAM

– Eight typical case studies

5.1 Theoretical presentationSession objectives

© Alcatel 271


5 CASE STUDIES

5.2 Tunnel Case


TUNNEL Case

RADAR Case

TOWER Case

RESURGENCE Case

FOREST Case

HIGHWAY Case



© Alcatel 272



5.2 Tunnel Case

> Radiating cable in a tunnel

Question:

� Risks of such a configuration

� Tune the right parameters for the tunnel cell

� Catch quickly ‘car traffic’

� Avoid the pedestrian traffic

Indoor BTS

Outdoor BTS

Pedestrianmobile

© Alcatel 273


5 CASE STUDIES

5.3 Radar Case


TUNNEL Case

RADAR Case

TOWER Case

RESURGENCE Case

FOREST Case

HIGHWAY Case



© Alcatel 274



5.3 Radar Case

> Radar situation

• A “radar” cell situated on top of a hill provides a wide coverage area.

• An industrial zone in the valley is covered by small cells but also by the “radar” cell. The serving areas in the IZ are not clearly defined.

> Objective

• Give a parameter set toprevent the radar cell from catching any traffic in the industrial zone by HO assignment

© Alcatel 275


5 CASE STUDIES

5.4 Tower Case


TUNNEL Case

RADAR Case

TOWER Case

RESURGENCE Case

FOREST Case

HIGHWAY Case



© Alcatel 276



5.4 Tower Case

> Tower situation

• The indoor mobile selects in idle mode the outdoor cell (same LA)

> Objective

• Define a set of parameters to avoid that effect

Outdoor cell

Indoorantenna

Indoormobile

© Alcatel 277


5 CASE STUDIES

5.5 Resurgence Case


TUNNEL Case

RADAR Case

TOWER Case

RESURGENCE Case

FOREST Case

HIGHWAY Case



© Alcatel 278



5.5 Resurgence Case

> Resurgence situation

• In rural network, especially in hilly landscape, many resurgences occur from very far cells.

> Objective

• Define a set of parameters to avoid radio link establishment to those cells and TCH traffic on those cells

Cell A

Resurgencefrom cell A

Cell B

25 Km

© Alcatel 279


5 CASE STUDIES

5.6 Forest Case


TUNNEL Case

RADAR Case

TOWER Case

RESURGENCE Case

FOREST Case

HIGHWAY Case



© Alcatel 280



5.6 Forest Case

> Forest situation: a highway crosses a forest

• High call drop rate (radio cause) on the cell and drive tests: strong level attenuation at the entrance of the forest

> Objective

• Define a set of parameters to avoid radio link failure

-75 dBm

-90 dBm

Forest(ATT = 10 dB every 100 m)

Highway

BTS

© Alcatel 281


5 CASE STUDIES

5.7 Highway Case


TUNNEL Case

RADAR Case

TOWER Case

RESURGENCE Case

FOREST Case

HIGHWAY Case



© Alcatel 282



5.7 Highway Case

> Highway situation:

• A highway is slightly covered (best coverage on 200m) by an ‘orthogonal’ cell (cell C on the map)

> Objective

• Define a set of parameters to avoid traffic in the ‘orthogonal cell’

Cell A

Cell B

Cell C

© Alcatel 283


5 CASE STUDIES

5.8 TCH/SDCCH congestion case


TUNNEL Case

RADAR Case

TOWER Case

RESURGENCE Case

FOREST Case

HIGHWAY Case



© Alcatel 284



5.8 TCH/SDCCH Congestion Case

> SDCCH congestion situation

• A railway station is located at the frontier of two LAs. Every train stopping in this station comes from LA 1 and then return to LA 1 after the stop.

> Objective

• Define a set of parameters to avoidSDCCH congestion on cell B (LA 2)

LA frontier

LA 1

LA 2

Cell A

Cell B

© Alcatel 285


5 CASE STUDIES

5.9 Indoor cell congestion case


TUNNEL Case

RADAR Case

TOWER Case

RESURGENCE Case

FOREST Case

HIGHWAY Case



© Alcatel 286



5.9 Indoor cell congestion

> An indoor microcell has been introduced within a multi-layer network (macro + micro)

> When the indoor microcell is congested, FDR may not be working as some the MSs can be covered only by this cell

• Define parameter settings to find a good solution in case of indoor cell congestion

City center

Micro-cells

Macro-Cell

Macro-CellMacro-Cell

© Alcatel 287



END SESSION

© Alcatel 288


ANNEXES

TYPICAL MODULE STRUCTURE

objective(s)

theoretical presentation

training exercises and/or cases study + feedback

© Alcatel 289


ANNEXES

Annex.1 Erlang B law

Erlang B law

Frequency hopping influence on PCHO process

Load & Traffic evaluation

Training exercises solutions

© Alcatel 290



Annex.1 Erlang B law Erlang definition

> ERLANG: unit used to quantify traffic

• Example:

– 1 TCH is observed during 1 hour

– one can observe 1 call of 80 sec and 1 call of 100 sec

– the observed traffic is T = (80+100)/3600 = 0.05 ERLANG

Erlang definition

T = total observation duration

resource usage duration(Erlang)

© Alcatel 291



> ERLANG <-> CALL MIX

• CALL MIX EXAMPLE

– 350 call/hour

– 3 LU/call

– TCH duration: 85 sec

– SDCCH duration: 4.5 sec

• ERLANG COMPUTATION

– TCH = (350 * 85)/3600 = 8.26 ERLANG

– SDCCH = [ (350 + 350*3) * 4.5 ] / 3600 = 1.75 ERLANG

Annex.1 Erlang B law Call mix definition

> 350 calls * 85 sec / 1 hour(3600 sec):

• TCH = (350 * 85)/3600 = 8.26 ERLANGS

> 350 calls means 350 SDCCH phases.

> 3 LU/call means 3 * 350 LUs so 1050 SDCCH phases more.

> 1 SDCCH phase is 4.5 sec:

• SDCCH = [ (350 + 350*3) * 4.5 ] / 3600 = 1.75 ERLANG

© Alcatel 292



Annex.1 Erlang B law Erlang B (1/5)

> ERLANG B LAW

• Relationship between

– offered traffic

– number of resources

– blocking rate

> In a telecom system, call arrival frequency is ruled by the POISSON LAW

1 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 970

1

2

3

4

5

6

7

8

9

10

Call

Second

> The offered traffic is the traffic asked by the customers.

> The graph gives the number of connection requests per second during 35 seconds.

> 83/30s => 83 * 2 * 60 = about 10 000 / hour

> Real example in Paris on 1 BSC (LA FOURCHE).

© Alcatel 293




> Call request arrival rate (and leaving) is not stable

• Number of resources = average number of requests * mean duration

• Is sometime not sufficient => probability of blocking

> => Erlang B law

• Pblock: blocking probability

• N: number of resources

• E: offered traffic [Erlang]

• Good approximation when the blocking rate is low (< 5%)

Pblock = ΣΣΣΣ

N

k=0E

k

k !

EN

N !

Erlang B law

© Alcatel 294



> There is two different ways to use this law

• Using Abacus

• Using SW (here Excel)

– Pblock = f (T, Nc)

– Offered = f (Nc, Pblock)

– Channels = f (T, Pblock)


© Alcatel 295




> Example:

We have a BTS of 8 TRXs (about 60 channels (Nc))

We do not want more than 2% of blocking (Pblock)

=> The traffic is not to be greater than 50 Erlangs (T)

• 83% of resources used to reach 2% of blocking

© Alcatel 296




> But be careful, the law is not linear:

• In B4, we use for example a combined BCCH with a micro BTS.

� 4 SDCCHs, Pblock = 2% => T = 1.1 E

� 25% of resources used to reach 2% of blocking

• In B5, if we decide to provide SMSCB (Cell Broadcast information)

� 1 subchannel SDCCH is therefore used.

� 3 SDCCHs, Pblock = 2% => T = 0.6 E

� 25% of resources less => 50% of Traffic less !!

© Alcatel 297



> CELL DIMENSIONING

• Given an Offered traffic, compute the number of TRXs (and SDCCHs) needed to carry it

• Default blocking rate

– RTCH: 2%

– SDCCH: 0.5%

– (TTCH: 0.1%)

Annex.1 Erlang B law Cell dimensioning (1/5)

© Alcatel 298



> CELL DIMENSIONING

• To handle an offered traffic of 12 Erlangs (TCH), compute the number of channels, then the number of TRXs

• Channels (12;2%) = 19

• Example: 3 TRXs , 21 TCHs, 1 BCCH, 2 SDCCH8


© Alcatel 299



> CELL DIMENSIONING, based on field measurement

• One is measuring a traffic of 15 Erlangs, with a blocking rate of 10%

• How to dimension the cell?

• Offered traffic = 15 / (1-10%) = 16.7 Erlangs !!!!

• Channels (16.7;2%) -> 25 TCHs -> 4 TRXs needed


© Alcatel 300



> FORECASTING TRAFFIC/CRITICAL TRAFFIC

• Traffic forecasting must be calculated according to offered traffic

� not directly on measured traffic

• In order to plan necessary actions soon enough, one must calculate regularly the date when the traffic of a cell will become critical

• Critical traffic: when offered traffic will induce 2% of blocking


© Alcatel 301




> WARNING: in case of too high blocking rate

• First check that there is no outage on the BTS

• Before starting a dimensioning/tuning action

© Alcatel 302



Annex.1 Erlang B law Training exercise

> Training exercise

Complete this form in order to get less than 2% of blocking in all cases.

Back

Erlang TCHoffered traffic

450 call/hourMean TCH call duration: 80 sec

Blocking rate TCH: 0.8%12,743 10.08 Erlang TCH

30% offered trafficincrease

13.1 Erlang TCH -> 20 TCH3 TRX

Call mix infoCell Traffic forecast Proposed configuration

12,675

12,865


Blocking rate TCH: 4%


Blocking rate TCH: 8%



cellcellcellcell call call call call mix infomix infomix infomix info Erlang TCHErlang TCHErlang TCHErlang TCH traffic traffic traffic traffic forecastforecastforecastforecast proposed proposed proposed proposed configconfigconfigconfig

12, 743 450 call/hourmean TCH call duration : 80secblocking rate TCH : 0.8%

10 Erlang TCH

(450*80)/3600=1010/.992=10.081

30 % TCH increase

10,081*1.3=13.1

13,1 Erlang TCH - > 20TCH

3 TRX

12,675 330 call/hourmean TCH call duration 129secblocking rate 4%

(330*129)/3600=11.825/0.96=12.3177

30 % TCH increase

12.3177*1.3 =16

16 Erlang TCH -> 24 TCH

4 TRX

12,865 600 call/hourmean TCH call duration 96secblocking rate 8 %

(600*96)/3600=16/.92 = 17.4

30 % TCH increase

17.4*1.3 = 22.6

22.6 Erlang TCH -> 31 TCH

5 TRX

© Alcatel 303


ANNEXES

Annex.2 Frequency Hopping influence on PCHO process

Erlang B law




© Alcatel 304



Annex.2 Frequency Hopping influence on PCHO process(1/4)

> Signal decoding process

• In a GSM system, the number of frames that are not erased are sent as an input to the voice decoder

Inside the mobile station

Decoder

Encoder

DeinterleaveError Correction

Frame ErasureDecision

RXQUAL Frame Erasure Rate

Demod.VoiceDecoder

Air

© Alcatel 305



> Quality impact of frequency hopping on the reception chain

• In non-hopping networks, the RXQUAL and voice quality are correlated

• In hopping networks, the voice quality is sooner correlated to the FER. This is due to interferer averaging and due to the non-linear mapping of BER to RXQUAL values.


© Alcatel 306



> Quality impact of frequency hopping on the reception chain

• FER is improved when frequency hopping is activated (cyclic or random)

• RxQual is not impacted whereas the speech quality is better


0

0.2

0.4

0.6

0.8

1

1.2

1.4

RxQ Average

0.00%

0.50%

1.00%

1.50%

2.00%

2.50%

FER Average

Ref Cyclic RandomRxQ AverageFER Average

© Alcatel 307



> Conclusion

• When frequency hopping is activated

• We can accept in Power Control and Handover processes, a threshold increase:

– OFFSET_HOPPING_PC and

– OFFSET_HOPPING_HO

Annex.2 Frequency Hopping influence on PCHO processConclusion (4/4)

Back

© Alcatel 308


ANNEXES

Annex.3 Load & Traffic evaluation

Erlang B law




© Alcatel 309



Annex.3 Load & Traffic evaluationCell TCH radio resource evaluation usage

Back - Cause 12

Back - Cause 26

FREEfactorLOADfactor

Loadevaluation

Speed discrimination for hierarchical networkFull Rate/Half Rate channel allocation

Power budget HandoverTraffic Handover

Multiband capture HandoverGeneral capture Handover

N_TRAFFIC_LOAD x A_TRAFFIC_LOAD x TCH_INFO_PERIOD

Shortterm

Mediumterm

Longterm

LOAD_EV_PERIOD x TCH_INFO_PERIOD

TCH_INFO_PERIOD

Period Usage

© Alcatel 310



Annex.3 Load & Traffic evaluationLoad evaluation (1/5)

Nb of free TCHsLOADfactorsFREEfactors

Load evaluation

TCH_INFO_PERIOD sec

LOAD_EV_PERIOD

Non-sliding average

> Medium term measurement of the load of a cell

• Corresponds to function AV_LOAD(cell)

• A new sample of the “Nb free TCH” in the cell is available every TCH_INFO_PERIOD seconds

• AV_LOAD() is a non-sliding window load average from Nb free TCH samples updated every LOAD_EV_PERIOD x TCH_INFO_PERIOD sec

© Alcatel 311




> AV_LOAD(cell n) calculated from N Nb free TCH samples available during LOAD_EV_PERIOD x TCH_INFO_PERIOD sec

• LOADfactors and FREEfactors also determined from Nb free TCH samples every TCH_INFO_PERIOD seconds (short term evaluation)

• LOADlevels are boundaries of load intervals associating a LOADfactor (db) to a Nb of free TCH samples

• FREElevels are boundaries of Nb of free TCH intervals associating a FREEfactor (db) to a Nb of free TCH samples

AV_LOADdefinition

AV_LOAD = Nsamples

1ΣΣΣΣ

Nsamples

i = 1

(1 - Nb total TCH (n)

Nb free TCH (n)) x 100

© Alcatel 312




> LOADfactor determination:

• LOADlevel in %

• LOADfactor in dB

LOADfactor

LOADfactor_1

LOADfactor_2

LOADfactor_3

LOADfactor_4

LOADfactor_5

t = (1 - Nb free TCH/Total Nb TCH) x 100

t <= LOADlevel_1

LOADlevel_1 < t <= LOADlevel_2



LOADlevel_4 < t

© Alcatel 313




> FREEfactor determination:

• FREElevel in absolute number of TCH

• FREEfactor in dB

FREEfactor

FREEfactor_1

FREEfactor_2

FREEfactor_3

FREEfactor_4

FREEfactor_5

Nb free TCH

t <= FREElevel_1

FREElevel_1 < t <= FREElevel_2



FREElevel_4 < t

© Alcatel 314




> Example: cells with 4 TRXs (28 TCHs)

In cell evaluation of cell n for outgoing HO from cell 0:

• In GRADE(n): + LOADfactor(n) = +0 = 0 dB

• In ORDER(n): + FREEfactor(n) – FREEfacfor(0) = +7 – (-8) = +15 dB

LOADfactor

+10 dB

+5 dB

0 dB

-10 dB

-15 dB

Load = (1 - Nb free TCH/Total Nb TCH) x 100

t <= 10%

10% < t <= 25%

25% < t <= 50%

50% < t <= 80%

80% < t

FREEfactor

-16 dB

-8 dB

0 dB

+7 dB

+10 dB

Nb free TCH

t <= 3

3 < t <= 8

8 < t <= 15

15 < t <= 21

21 < t

Cell nCell 0

HO ?Nb free TCHs = 4Load = 85.7%

LOADfactor(0) = -15 dBmFREEfactor(0) = -8 dBm

Nb free TCHs = 20Load = 28.6%

LOADfactor(n) = 0 dBmFREEfactor(n) = +7 dBm

© Alcatel 315



Annex.3 Load & Traffic evaluationTraffic evaluation (1/4)

> Long term measurement of the load of a cell

• Corresponds to function Traffic_load(cell)

• Traffic_load() value is determined from a number N_TRAFFIC_LOAD of consecutive non-sliding window load averages AV_TRAFFIC_LOAD calculated from Nb of free TCH samples updated every A_TRAFFIC_LOAD x TCH_INFO_PERIOD sec

Nb of free TCHsLOADfactorsFREEfactors

Traffic evaluation

TCH_INFO_PERIOD sec

A_TRAFFIC_LOAD(N_TRAFFIC_LOAD non-sliding average)

TRAFFIC_EV_PERIOD

© Alcatel 316




• 3 possible values for Traffic_load(): high, low, indefinite

• Initialization: Traffic_load() = indefinite

• Traffic_load() becomes:

– High if the last N_TRAFFIC_LOAD consecutiveAV_TRAFFIC_LOAD load averages are all greater than HIGH_TRAFFIC_LOAD threshold

– Low if the last N_TRAFFIC_LOAD consecutiveAV_TRAFFIC_LOAD load averages are all lower than LOW_TRAFFIC_LOAD threshold

Traffic loadThresolds comparisonwith N_TRAFFIC_LOAD

averages

AV_TRAFFIC_LOADAveraging onA_TRAFFIC_LOAD

load samples

Load samples

HIGH_TRAFFIC_LOAD

LOW_TRAFFIC_LOAD

IND_TRAFFIC_LOAD

© Alcatel 317



• Traffic_load() becomes indefinite if:

– Traffic_load() was high and the last AV_TRAFFIC_LOAD load average is lower than LOW_TRAFFIC_LOAD (or IND_TRAFFIC_LOAD if not 0%)

– Traffic_load() was low and the last AV_TRAFFIC_LOAD load average is greater than HIGH_TRAFFIC_LOAD (or IND_TRAFFIC_LOAD if not 0%)

• Traffic_load(n) is always equal to indefinite if cell n is external to BSC

• HIGH_TRAFFIC_LOAD ≥ IND_TRAFFIC_LOAD ≥LOW_TRAFFIC_LOAD


© Alcatel 318




HIGH_TRAFFIC_LOAD

Variation ofAV_TRAFFIC_LOAD

IND_TRAFFIC_LOAD

LOW_TRAFFIC_LOAD

Traffic_load = high

Traffic_load =indefinite


Traffic_load = low Traffic_load = low



Traffic_load = high

IND_TRAFFIC_LOAD = 0IND_TRAFFIC_LOAD <> 0

> Example with N_TRAFFIC_LOAD = 3

Back - Cause 12 Back - Cause 26

© Alcatel 319


ANNEXES

Annex.4 Handover Management

Erlang B law




© Alcatel 320



> Handover Management made up of:

• Cell Filtering Process (according to call history)

• Handover Decision (according to the best cell in the list)

> Handover Management followed by:

• Handover Protocol

Annex.4 Handover Management Principles

Radio

Link

Measurements

Active

Channel

Pre-processing

BTS BSC

HO DetectionHO Candidate

Cell Evaluation

HO

management

MSC

HO

protocol

HO Preparation

© Alcatel 321



Annex.4 Handover Management Global Handover Process

Handover preparation

Handoverdetection

Handover management

Cellfilteringprocess

Handoverprotocol

Externalor internalchannelchange

Candidate cell

evaluation

Handoverdecision

Rawcell list

Orderedtargetcell list

Filteredtargetcell list

Executiontargetcell list

© Alcatel 322



> Three cell lists:

• Ordered target Cell list

– target cells provided by Candidate Cell Evaluation

• REJ_CELL_LIST

– cells internally rejected by the MSC or BSC

• MS_CELL_REJ_LIST

– cells to which the MS failed to hand over

Annex.4 Handover Management Cell Lists usage

> Since B6 release, some changes have been provided to the HO management process which is in charge of the HO execution triggering, when the need of handover is detected by the HO preparation process.

> These changes are :

• use of the T_FILTER parameter in a different way than for B5,

• the parameter NBR_HO_ATTEMPTS which was used for internal HO in B5 is removed,

• use of the T7 parameter and of the REJ_CELL_LIST list also for internal HO in B7,

• same behavior in case of internal and external HO in B7,

• immediate attempt after rejection or failure without waiting for a new alarm in case of internal and external HO in B7,

• implicit rejection of cells in B7 with the help of the target cell identity in the HO command received from the MSC.

© Alcatel 323



> T_FILTER: controls the global handover procedure

• started: when a cell list is to be sent by Candidate Cell Evaluation

• expiry ⇒ empty target cell list sent to the Handover Management

> T7: controls the clean-up of REJ_CELL_LIST

• started: when a target cell list is to be sent to Handover Protocol

• expiry ⇒ empty REJ_CELL_LIST

> T_MS_CELL_REJ: clean-up of MS_CELL_REJ_LIST

• started: when an MS reports a failure to seize the target channel

• expiry ⇒ empty MS_CELL_REJ_LIST

> T_HO_REQ_LOST: to supervise answer of MSC (no HANDOVER REQUIRED REJECT message sent)

• Started: HO REQUIRED sent

• Stopped: HO COMMAND received

• Expiry ⇒ external channel change procedure is terminated.

Annex.4 Handover Management Timers usage

> If the candidate cell list provided by the candidate cell evaluation process is different from the previous one (the number of cells is different or same number of cells but new cells in the list), an alarm is sent to the HOM process. In B7, if T_FILTER expires, it means that the HO is no more necessary.

> For both internal and external HOs in case of HO failure from the MS, the cell is filtered until the expiry of the T_MS_CELL_REJ timer. When the T_MS_CELL_REJ timer expires, the rejected cell may be a candidate.

> In B7 release, T7 timer is used to manage the REJ_CELL_LIST list and a subsequent HO REQUIRED can be sent to the MSC before T7 expiry if the target cell list has changed (new cell or removed cell).

> The REJ_CELL_LIST list is used for both internal and external Hos.

> T_HO_REQD_LOST Expiry

• This timer is used to supervise response from the MSC. It is started when sending the first HANDOVER REQUIRED to the MSC and it is stopped in the following cases:

• when HANDOVER COMMAND is received from the MSC or

> when HANDOVER REQUIRED REJECT is received from the MSC only if the same number of HANDOVER REQUIRED REJECT messages have been received from the MSC than the number of HANDOVER REQUIRED messages sent to the MSC for this channel change procedure) (i.e. no message crossing over A interface).

• In case where more HANDOVER REQUIRED messages have been sent to the MSC, the timer T_HO_REQD_LOST is not stopped upon HANDOVER REQUIRED REJECT receipt, as there is no way for the BSC to know if the received HANDOVER REQUIRED REJECT is a response to the last HANDOVER REQUIRED message or a response to a previous one (message crossing over A interface).

• On expiry, an O&M error report is raised only when no message has been received from the MSC since the last HANDOVER REQUIRED message, and the external channel change procedure is terminated.

© Alcatel 324



Annex.4 Handover Management Handover Execution Process

Handover preparation

Cell filtering process

remove cells previously rejectedfrom MSC or BSC

remove cells previously rejected

for MS failure reason

remove cells not suitable due toO&M reason


Cell 4

Cell 2

Cell 8


Cell 2

Internal

Handover

InternalHandover

Handoverprotocol

Handover decision

Relevant handover protocol ischosen according to the type of

GSM procedure ongoing and thefirst target cell of the list

T7 is started

List of cellspreviously rejected

for MS failure

Cell 8

MS_CELL_REJ_LIST listcleared atT_MS_CELL_REJ expiry

List of cellspreviously rejectedfrom MSC or BSC

Cell 4

REJ_CELL_LIST listcleared at T7 expiry

© Alcatel 325



Annex.4 Handover Management HO execution example

Handover management

Orderedtarget cell list

Cell 1Cell 2Cell 3

Rejected lists

MS emptyBSC/MSC empty


Cell 1Cell 2Cell 3

Update

Cell 1 -> MSrejected list

Handover management


Cell 1Cell 2Cell 3

Rejected lists

MS cell 1BSC/MSC empty


Cell 1Cell 2Cell 3

Handoverprotocol

HO fails

on cell 2

ROC

Update

T_MS_CELL_REJ

expires

MS rejected listempty

Update

Cell 2 -> MS

rejected list

Cell 1 -> BSCrejected list

Handover management


Cell 1Cell 2Cell 3

Rejected lists

MS cell 2BSC/MSC cell 1


Cell 1Cell 2Cell 3

Handoverprotocol

HO tocell 3

Handoverprotocol

HO failson cell 1

ROC

© Alcatel 326



> End of Handover procedure = T_FILTER timer expiry

• T_FILTER restarted each time a target cell list is to be sent by

Candidate Cell Evaluation to the Handover Management (same

list than the one previously sent or not)

• The target cell list is sent to the Handover Management if different

from the last target cell list previously sent

• T_FILTER expiry means no handover is needed anymore

Annex.4 Handover Management T_FILTER controls HO procedure (1/2)

© Alcatel 327



Annex.4 Handover Management T_FILTER controls HO procedure (2/2)

Back

Is T_FILTER running?

YesNo

Restart T_FILTER

New candidate cell list from thecandidate cell evaluation function

Start T_FILTER:an HO alarm containing thecandidate cell is sent to theHO management entity

YesNo

Is the candidate cell listdifferent from the previous one?

Restart T_FILTER:an HO alarm containing thecandidate cell is sent to theHO management entity

No Handover is on-going A Handover is on-going

A Handover is now on-going

T_FILTER is restartedeach time the alarm is still on

© Alcatel 328


ANNEXES

Annex.5 LCS

Erlang B law




© Alcatel 329



Annex.5 LCS Definitions

> New end-user services which provide the geographical location of an MS:

– On MS request to know its own location

– On network request (especially during Emergency calls)

– On external request (LCS Client)

> Several positioning methods:

– Cell-ID or Cell-ID + TA (Timing Advance)

– Conventional (standalone) GPS

– Assisted GPS (with A-GPS server help to compute location)

– MS-based (MB): the MS is able to perform a pre-computation

– MS-assisted (MA): the MS sends info, Network computes

> Assisted GPS Method:

• Mobile-based: The MS performs OTD signal measurements and computes its own location estimate. In this case, the network provides the MS with the additional information such as BTS coordinates and the RTD values. These assistance data can be either broadcast on the CBCH (using SMSCB function) or provided by the BSS in a point-to-point connection (either spontaneously or on request from the MS).

• Mobile-assisted: The MS performs and reports OTD signal measurements to the network and the network computes the MS’s location estimate.

• With

– OTD: Observed Time Difference: the time interval that is observed by an MS between the receptions of signals (bursts) from two different BTSs.

– RTD: Real Time Difference: This means the relative synchronization difference in the network between two BTSs.

> Finally, 4 methods are possible for positioning:

• Cell ID+ TA,

– This is the simplest method for determining the location of a mobile. It relies on the hypothesis that the geographical coverage of a cell corresponds to that predicted by radio coverage studies. When an active mobile is connected to a base station, the mobile is assumed to be located geographically within the area predicted to be best served by this base station

• Conventional (MS equipped with GPS System),

• MS-based Assisted GPS,

• MS-Assisted GPS.

© Alcatel 330



Annex.5 LCS LCS architecture

> LCS function: Architecture MS Request1

Network Request2

External Request3

A-GPSGMLCLCSSMLC

: Assisted GPS: Gateway Mobile Location Center: Location Services: Serving Mobile Location Center

BTS

Abis

MFS

BTS

OSP

SMLC

A-GPSserver

GPS receiversreference network

GMLCExternalLCS client

MSCBSC

HLR

Abis

A Lg Le

Lh

Lb

Emergency call

2 3

SAGI

Where isthe accident?

Where ismy son?

Where am I?

1

SMLC function integrated in MFS:- receives the location request from the GMLC through the MSC/BSC- schedules all the necessary actions to get MS location- computes MS location- provides the result back to the GMLC

© Alcatel 331



Annex.5 LCS LCS Positionning procedure

BTS

MFS

BTS

OSP

SMLC

GMLCMSC

BSC

HLR

Locationrequest

1

Routinginformation

2

Providesubscriberlocation

3

Paging,authentication,ciphering,notification

4

Providesubscriber location

5

Individualpositioning

6 Location report7 7

Locationresponse

8

> If the MS is in idle mode, the MSC first performs a CS paging, authentication and ciphering in order to establish an SDCCH with the MS. The MS subscriber is not aware of it, i.e. no ringing tone, except towards GPRS MS in Packet Transfer Mode which may suspend its GPRS traffic in order to answer to the CS Paging (i.e. not fully transparent for the subscriber).

>

> When the MS is in dedicated mode (after a specific SDCCH establishment for location, or during an on-going call), the MSC sends the location request to BSC in the existing SCCP connection for the current call, which forwards it to the SMLC

© Alcatel 332



Annex.5 LCS LCS protocol (1/2)

BSCSMLC(MFS)

Um Lb

L1-GSL

L2-GSL

BSSLAP

L2-GSL

BSSAP-LE

L1-GSLL1

L2(LAPDm)

RR

Relay

RRLP(04.31)

BSSLAP(08.71)

BSSAP-LE(09.31)

Target MS

L1

RR(04.18)

L2(LAPDm)

RRLP(04.31)

Signaling Protocols between the MS (CS domain) and the SMLC

© Alcatel 333



Annex.5 LCS LCS protocol (2/2)

> Example: Mobile terminated location request success (External request)MS BTS BSC SMLC MSC GMLC HLR

Adequate positioning method

chosen by SMLC withoptional additional scenario

StartsT_Location

StopT_Location

LCS Service Request

Send_Routing_Info request

Send_Routing_Info response

Provide_Subscriber_Location

Authentication + Ciphering

BSSMAP Perform_Location_Request

BSSAP-LE Perform_Location_Request

BSSAP-LE Perform_Location_Response

BSSMAP Perform_Location_Response

Provide_Subscriber_Location Result

LCS Service Response

MSSMAP Clear Command and Release

LCS client

Paging

> T_location_Longer used in case of optional additional scenario (see graph):

Upon receipt of the MS POSITION COMMAND message from the SMLC (optional additional scenario), the BSC stops the T_Location timer, and starts instead the T_Location_Longer timer. This timer is stopped only at the end of the location procedure in the BSC, i.e. when an 08.08 PERFORM LOCATION RESPONSE message is sent back to the MSC.

> Aborts:

• Abort by MSC

Depending on the location procedure and its current state of execution, upon PERFORM LOCATION ABORT message receipt, the BSC sends immediately to the MSC a PERFORM LOCATION RESPONSE message (when no exchange on the Lb interface is on-going), or to the SMLC either a PERFORM LOCATION ABORT or an ABORT message. The BSC starts the timer T_Loc_abort to supervise the SMLC response.

• Abort by BSS

If an ongoing location request is interrupted at the BSC level for the following reasons:

– by an inter-BSC handover, or

– if the main signaling link to the target MS is lost or released, or

– the SCCP connection on the A interface is released, or

– if the timer T_Location expires,

the BSC must send either a PERFORM LOCATION ABORT message or a ABORT message to the SMLC and starts the timer T_Loc_abort

> The useful B8 content of the received PERFORM LOCATION REQUEST message is:

• Location type,

• Classmark information 3,

• Requested QoS: provides service requirement concerning geographic positioning and response time

– accuracy, the response time category (Low Delay or Delay Tolerant),

• Current Cell Id + TA information are always provided to the SMLC.

> The time of transfer of the assitance data on the SDCCH is estimated about 14s for a 1000 octets information,

© Alcatel 334



Annex.5 LCS Positioning methods : CI+TA positioning

> Principles of CI + TA Positioning Method

LCS_LONGITUDE

LCS_LATITUDE

LCS_AZIMUTH(Main Beam Directiongiven by the azimuth)

HALFPWR_BEAM_W

IDTH

Serving cell (CI)

TA

3dB pointgiven by the azimuth

and the HPBW

3dB pointgiven by the azimuth

and the HPBW

553 m

MSestimated location

> With the TA positioning method, no signalling exchange is required between the SMLC and the MS (i.e. RRLP protocol is not required). The TA positioning method is applicable to all the MSs (supporting LCS or not).

> Based on:

• Cell Identity (CI) of the serving cell and

• Timing Advance (TA) value reported by MS

� intersection point of a line from the BTS antenna in their main direction with a circle which radius is corresponding with the propagation delay (timing advance) is the MS estimated position

� Omni-directional cells: MS position = site position

> Parameters:

> EN_LCS – flag to enable/disable the Location Services per BSS

• 0 = Enabled; 1= Disabled; Default = 0

�� IF EN_LCS=1, CI+TA method is enabled in all the BSS cells

• LCS_LATITUDE

– Latitude of the BTS supporting the cell

• LCS_LONGITUDE

– Longitude of the BTS supporting the cell

• LCS_AZIMUTH

– Antenna direction orientation for the sector supporting the cell

• HALFPWR_BEAM_WIDTH

– Antenna half power beamwidth for the sector supporting the cell

> Optimization parameters:• ARC_SIZE_FACTOR

– Factor used in the computation of the width in degree of the ellipsoid arc returned by the MFS when computing location estimate based on TA positioning method.

• MIN_RADIUS_FACTOR

– Factor used in the computation of the minimum radius of the ellipsoid arc returned by the MFS when computing location estimate based on TA positioning method

• MAX_RADIUS_FACTOR

– Factor used in the computation of the maximum radius of the ellipsoid arc returned by the MFS when computing location estimate based on TA positioning method

© Alcatel 335



Annex.5 LCS Positioning methods : Conventional GPS

> Conventional GPS location procedure

• This optional location procedure is chosen by the SMLC (if the MS support it) upon reception of a Perform Location Request message from the BSC

PerformLocationRequest

MS BTS BSC SMLC

Measurement Position Request

Measurement Position Response (X,Y)

PerformLocation

Response (X,Y)(X,Y):

computed position

(X,Y)

LocationRequest

LocationResponse

• The MS continiously computes its position

• Terminal searches for satellites, acquires all the GPS data, computes its own position and finally provides the location estimation to the SMLC

© Alcatel 336



Annex.5 LCS Positioning method : Assisted GPS Positioning 1/3

> Assisted GPS Positioning Method (A-GPS)

• Assistance GPS Positioning Method is split into:

– MS Based A-GPS method

– MS Assisted A-GPS method

- GPS acquisition assistance- Navigation model (almanac, ephemeris)- Ionospheric model- Time integrity

GPS MS A-GPSserver

GPS receiversreference network

Assistance data on request

> Assistance data gathered from a GPS reference network receiver is broadcasted to the GPS MS

> Flags/Parameters

• EN_LCS = 1

• EN_MS_BASED_AGPS – enables/disables the positioning method MS Based A-GPS per CELL

– 0 = disabled; 1 = enabled; default = 0

• EN_MS_ASSISTED_AGPS – enables/disables the positioning method MS Assisted A-GPS per CELL

– 0 = disabled; 1 = enabled; default = 0

© Alcatel 337




> A-GPS location procedure / MS Based A-GPS


MS BTS BSC SMLC

LocationRequest

A-GPSServer

GPS infoRequest

GPS infoResponse


Assistance Data

Assistance Data Acknowledge

Measurement Position Response (X,Y)

PerformLocation

Response (X,Y)

LocationResponse

PositionRequest

PositionResponse

AssistanceData

(X,Y)

(X,Y):computed position

Positioning calculation:latitude, longitude

and altitude

> Using assistance data, MS computes by itself the position and sends it back to the SMLC

© Alcatel 338




> A-GPS location procedure / MS Assisted A-GPS

(X,Y):computed position

Pseudo-rangemeasurements (M)

PositionResponse


MS BTS BSC SMLC

LocationRequest

A-GPSServer

GPS infoRequest

GPS infoResponse


Assistance Data

Assistance Data Acknowledge

PerformLocation

Response (X,Y)

LocationResponse

PositionRequest

AssistanceData

(X,Y)

Measurement Position Response (M)

GPS LocationRequest (M)

GPS LocationResponse (X,Y)

• Using a reduced set of assistance data, the MS makes pseudo–range measurements and sends the result to the A-GPS server, which fixes the position in the end

© Alcatel 339



Annex.5 LCS LCS impact on HO 1/3

> HO preparation

• Inhibition of “better cell handovers”

• Other HOMS BTS BSC SMLC MSC GMLC HLR

StartsT_Location

EmergencyHO

detection

LCS Service Request

Send_Routing_Info request

Send_Routing_Info response

Provide_Subscriber_Location

Authentication + Ciphering


BSSAP-LE Perform_Location_Request

LCS client

Paging

BSSLAP - Reset

– HO needed during LCS procedure

© Alcatel 340




> HO management

• Internal HO

MS BTS BSC SMLC MSC GMLC HLR

HOcomplete



LCS client

BSSLAP - Reset

Intra BSCHO

on going

BSSMAP perform location response (cause = "Intra-BSC Handover Complete)

– Mobile in communication

© Alcatel 341




> HO management

• External HO

MS BTS Serving BSC SMLC MSC GMLC HLR

ExternalBSC HO

BSSAP-LE Perform_Location_Abort

LCS client


BSSMAP HO required


© Alcatel 342



Annex.5 LCS BSS Parameters

Timers

T_Location

T_Location_longer

T_Loc_Abort

T_LCS_delay_tolerant

T_LCS_LowDelay

T_RRLP_low_delay

T_RRLP_delay_tolerant

FLAGS

EN_LCS

EN_SAGI

OPTIMIZATION DATA

ARC_SIZE_FACTOR

MIN_RADIUS_FACTOR

MAX_RADIUS_FACTOR

> BSS PARAMETERS

– EN_LCS (BSC)– Flag which enables or disables the LCS feature in the BSS.

– EN_SAGI– Flag indicating whether SAGI is configured or not for this BSS

– T_Location:– BSC timer on a per call basis to guard the response from the SMLC in case of Location Request, when no RRLP

exchange is triggered with the MS.– T_Location_longer:

– BSC timer on a per call basis to guard the response from the SMLC in case of Location Request, when an RRLP exchange is triggered with the MS. Replace T_Location timer in case of Conventional GPS, MS-Assisted A-GPS, MS-Based A-GPS.

– T_Loc_Abort– BSC timer to guard the response from the SMLC in case of Location Abort.

– T_LCS_LowDelay– SMLC timer to guard the calculation of the MS position (including the RRLP message exchange with the

target MS) in case of a Low Delay Location Request.– T_LCS_DelayTolerant

– SMLC timer to guard the calculation of the MS position (including the RRLP message exchange with the target MS) in case of a Delay Tolerant Location Request.

– T_LCS_LowDelay

– SMLC timer to guard the calculation of the MS position (including the RRLP message exchange with the target MS) in case of a Low Delay Location Request.

– T_RRLP_Low_delay– Timer to guard the RRLP exchange between the SMLC and the MS .

– T_RRLP_delay_tolerant– Timer to guard the RRLP exchange between the SMLC and the MS.

• Optimization data:

• ARC_SIZE_FACTOR– Factor used in the computation of the width in degree of the ellipsoid arc returned by the MFS when computing

location estimate based on TA positioning method. • MIN_RADIUS_FACTOR


• MAX_RADIUS_FACTOR – Factor used in the computation of the maximum radius of the ellipsoid arc returned by the MFS when computing

location estimate based on TA positioning method

© Alcatel 343



Annex.5 LCS Cell Parameters

SITE DATA

LCS_LATITUDE

LCS_LONGITUDE

LCS_SIGNIFICANT_GC

LCS_AZIMUTH

HALF_POWER_BANDWIDTH

EN_CONV_GPS

EN_MS_ASSISTED_AGPS

EN_MS_BASED_AGPS

FLAGS

> CELL PARAMETERS• EN_CONV_GPS

– Flag to enable/disable the Conventional GPS positioning method.• EN_MS_ASSISTED_AGPS

– Flag to enable/disable the MS Assisted A-GPS positioning method.• EN_MS_BASED_AGPS

– Flag to enable/disable the MS Based A-GPS positioning method. • LCS_LATITUDE

– Latitude of the BTS supporting the cell (used by the MFS to compute location estimate based on TA positioning method).

• LCS_LONGITUDE – Longitude of the BTS supporting the cell (used by the MFS to compute location estimate based on TA positioning

method). • LCS_SIGNIFICANT_GC

– Indicates whether latitude and longitude are significant or not • LCS_AZIMUTH

– Antenna direction orientation for the sector supporting the cell (used by the MFS to compute location estimate based on TA positioning method).

• HALF_POWER_BANDWIDTH – Half power beam width of the antenna for the sector supporting the cell (used by the MFS to compute location

estimate based on TA positioning method).

• Remark: To have LCS supported for a cell, the operator must activate LCS on the BSS handling this cell but he must also activate GPRS for this cell (i.e. setting of MAX_PDCH to a value > 0, the cell being kept locked for GPRS if the operator does not want to have GPRS running on this cell) and configure all the required transmission resources (Ater and Gbresources) on the GPU(s) connected to this BSC

© Alcatel 344



Annex.5 LCS Exercise

> Where is implemented the SMLC function?

> What are the LCS impacts on cell dimensioning?

Time allowed:

10 minutes

© Alcatel 345



Annex.5 LCSPositioning methods : CI+TA positioning

> Ellipsoid arc definition:

• Point (O)= serving BTS site coordinate

• θ= serving cell antenna azimuth - β /2

• β =A*width of serving cell sector in [°],calculated from bisector anglesof co-sited antenna azimuths

• r1= inner radius ofTA ring-(B-0.5)*554 in [m]

• R2=(B+C)*554 in [m]

– A: ARC_SIZE_FACTOR

– B: MIN_RADIUS_FACTOR

– C: MAX_RADIUS_FACTOR

Back

Serving cell (CI)

E

North

S

Wβ

θ

r1

r2

Point (O)

> An ellipsoid arc is a shape characterised by the co-ordinates of an ellipsoid point o (the origin), inner radius r1, uncertainty radiusr2, both radii being geodesic distances over the surface of the ellipsoid, the offset angle (θ) between the first defining radius of the ellipsoid arc and North, and the included angle (β) being the angle between the first and second defining radii. The offset angle is within the range of 0° to 359,999…° while the included angle is within the range from 0,000…1° to 360°. This is to be able to describe a full circle, 0° to 360°

> For CI+TA method which is default one , the answer is given by description of "ellipsoid arc".

> Optimization parameters:• ARC_SIZE_FACTOR

– Factor used in the computation of the width in degree of the ellipsoid arc returned by the MFS when computing location estimate based on TA positioning method.

• MIN_RADIUS_FACTOR


• MAX_RADIUS_FACTOR

– Factor used in the computation of the maximum radius of the ellipsoid arc returned by the MFS when computing location estimate based on TA positioning method

Date post:	06-Mar-2015
Category:	Documents
Upload:	saad-farooq
View:	126 times
Download:	8 times

Microsoft Power Point - RFT-B9

Documents