39034739-Handover-Training

Huawei Confidential

OMF010002 HandoverOMF010002 Handover

2

Summary of Handover

HO Algorithm process

HO Data Configuration

HO Signaling process

Course Contents

3

Summary of HO—Purposes of HO

• Purposes of HO To keep a continuous communication with a

moving MS

To improve network service performance

• To reduce the call drop rate

• To reduce the congestion rate

4

• Classification of HO: Emergency HO

• Timing Advance (TA) Emergency HO• Bad quality (BQ) Emergency HO • Rx_Level_Drop Emergency HO• Interference Emergency HO

load HO Normal HO

• Edge HO• Layer HO• Power Budget (PBGT) HO

Speed-sensitive HO (Fast moving MS HO) Concentric Cell HO

Summary of HO—Classification of HO

5

Summary of Handover (HO)




Course Contents

6

• General HO process

• Measurement report preprocessing

• Penalty processing

• Basic ranking and Secondary ranking

• HO judgment


7

General process of HO Algorithm

M.R.preprocessing

Penalty processing

Basic ranking

Secondary ranking

HO judgement

TA emergency HO

BQ emergency HO

RSD emergency HO

Interf. emergency HO

Load Sharing HO

Edge HO

Layer HO

PBGT HO

Processing program

OM forced HO

Directed retry

Overlaid/underlaid HO

Fast moving MS HO

1

1

8





• Basic ranking and secondary ranking

• HO judgment

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Measurement Report Preprocessing

• Measurement Report (MR): Uplink MR includes uplink receiving level and

quality.

Downlink MR includes downlink receiving level, downlink receiving quality of the serving cell and other downlink receiving levels from the neighbor cells.

Serving cell Neighbour cell

The downlink measurement report of the neighbour cell (BCCH)

The downlink measurement report of the serving cell

The uplink measurement report of MS

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Measurement Report Preprocess

• MR interpolation Every time BSC receives a measurement report,

there will be an update to the basic rank of the cells.

BTS may fail to receive the measurement report from MS. Before the rank-update, BSC needs to recover the lost measurement reports according to Filter Table. If the lost MR amount is within the allowed range, then recovers the lost MR according to the algorithm.

13

How to interpolate MR?

MR MR MR MR MR

Measurement report No. n

Measurement report No. n+4

Continuous MR flow

Measurement Report Preprocess

15




• Basic ranking and secondary ranking

• HO judgment


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Penalty Processing

• There are altogether four types of penalty process (second step of HO algorithm process )

Penalty on the target cell when a HO fails. Penalty on the original serving cell when an emergen

cy HO ( base on BQ and TA ) is performed. Penalty on other high priority layer cells after a fast m

oving HO is performed. A new HO attempt is prohibited within the penalty ti

me after an overlaid/underlaid HO fails.

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BTS

HO failure

BSC

Cell A

Cell B

Penalty Processing

• Penalty on the target cell: Punish the target cell when a HO fails. This is to avoid

the MS to select this cell again in next HO judgment.

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BTS

BQ& TA HO

BSC

Cell A

Cell B

Penalty Processing

• Penalty on the serving cell: Punish the original serving cell when an emergency HO

( due to BQ and TA) occurs.

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Back? No way!Back? No way!

Umbrella

Micro cell

Penalty Processing

• Giving penalty on the other three layers after MS handovers to Umbrella cell by fast-moving-HO. This is to keep MS staying in the umbrella cell and avoid frequent HO.

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Underlaid

Overlaid Do not attempt

again after a

failed HO!

Penalty Processing

• A new Overlaid/underlaid HO is prohibited within a penalty time after an Overlaid/Underlaid HO failure.

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• General HO process• Measurement report preprocessing• Penalty processing• Basic ranking and secondary ranking • HO judgment

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Basic Ranking and Secondary Ranking

• Basic ranking and secondary ranking of cells are major parts of the HO judgment. Ranking is made through 16bits-algorithm. The serving cell and the neighbor cells will be listed in a cell list according to their 16bits value. The ranking processes include:

M rule

K rule

16bits ranking

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M rule:

Only the cells with received signal level satisfy the following conditions can be put into t

he candidate cell list.

For serving cell: RX_LEV (o) >MSRXMIN(o) + MAX(0,Pa(o))

i.e : RX_LEV(o) – MSRXMIN(o)-MAX(0,Pa(o)) > 0 ……….. ( 1 )

For Neighbor cell: RX_LEV (n) > MSRXMIN(n)+ MAX(0,Pa(n))+ OFFSET

i.e : Having the same formula as above

Pa(0) : MS_TXPWR_MAX(0) – P

Pa(n) : MS_TXPWR_MAX(n) – P

MS_TXPWR_MAX( ) : The appointed MS transmitting power by the BSS.

P : Max_Power_of_MS

Max_Power_of_MS : MS maximum transmitting power

Basic ranking and Secondary ranking

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• K rule Criterion: After the M rule , the serving cell and candidate neighb

or cells are ranked in descending order according to the receiving level only.


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• The 16bits rule Both the serving cell and the neighbor cells have

their own 16bits value. The smaller the value is, the higher the priority and position the cell is in the cell list.

The 1st-3rd bits: bit value is decided according to the cell signal level and the penalty process taking place beforehand.

• The values come from max. 6 candidate cells and 1 serving cell according to the level ranges from 000~110. The value for the cell with the strongest signal level is 000.

16 9101112131415 12345678


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The 4th bit: bit value is determined by inter-cell HO ( of the same layer ) hysteresis.

• The 4th bit of the serving cell is always 0,

• The receiving signal level of the neighbor cell >= The receiving level of the serving cell + Inter-cell HO ( of the same layer ) hysteresis, bit 4th is set to 0.

• The receiving level of the neighbor cell < The receiving level of the serving cell + Inter-cell HO ( of the same layer ) hysteresis, bit 4th is set to 1.

– Note: In PBGT HO, whichever the greater of the inter-cell ( of the same layer ) hysteresis and PBGT threshold, that value will be used in the PBGT HO.

16 9101112131415 12345678


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The 5th-10th bits: bit value is decided according to their position in Huawei hierarchical network structure.

• When the signal level of the neighbor cells or the serving cell is lower than the layer HO threshold and hysteresis, this function is turned off and all bits are set to 0.

• That is to say only when the above criterions are met, then this function take effect.

• Huawei cell layers can be divided into 4 layers and each layer can be further divided into 16 different priorities. So there are 64 different priorities in Huawei hierarchical cell structure.

16 9101112131415 12345678


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GSM900 Cell

Micro Cell

Umbrella Cell GSM 900

GSM1800 GSM1800GSM1800

GSM 900 GSM 900 GSM 900

GSM900GSM900

GSM1800GSM1800

GSM900 GSM900

GSM1800 GSM1800

GSM1800 Cell

• Hierarchical cell structure


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The 11th bit: bit value is decided by cell-load-sharing criterion.

• Serving cell: if Cell Load>= Start threshold of load HO, bit 11th is set to 1, otherwise is set to 0.

• Neighbor cell: if Cell Load>=Receive threshold of load HO, bit 11th is set to 1, otherwise is set to 0.

• Refer to Load HO Table for the load HO threshold and load req. on candidate cell.

– Clue : When the cell load is higher than the threshold, then the bit 11th is set to 1.This is done in order to put the cell in a lower part of the cell list.

16 9101112131415 12345678


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12th bit: bit value is decided by co-BSC criterion.

• Serving cell: is always set to 0.

• Neighbor cell: if co-BSC with the serving cell, 12th bit is set to 0, otherwise is set to 1.

• When the signal level from the neighbor cell or the serving cell is lower than layer HO threshold and hysteresis. This function is turned off and the value is set to 0.

• If the parameter – “Co-BSC/MSC Adj.” in the HO control table is set to “No”, then this function is turned off and the value is 0.

13th bit : Bit value is decided by Co-MSC parameter, having the same concept as the 12th bit.

16 9101112131415 12345678


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The 14th bit: Layer HO threshold adjustment bit• Serving cell criterion:

– Receive level >= layer HO threshold – layer HO hysteresis, bit 14th is set to 0. At the same time, bit 13th, 12th and 10th—5th bits are set to 0.

– If the above criterion is not met, then bit 14th is set to 1.

– Example : 20-5 = 15 ( -95 dBm )

16 9101112131415 12345678


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• Neighbor cell criterion: – Receive level >=layer HO threshold + layer HO hyste

resis, bit 14th is set to 0. At the same time, bit 13th, 12th and 10th—5th bits are set to 0

– If the above criterion is not met, then bit 14th is set to 1.

– Example : 20+5 = 25 ( -85 dBm )• note :

– The layer HO threshold and hierarchical hysteresis correspond to the value of that individual cell’s value.

– Usual situation : When the neighbor cells are of the same layer, each of the neighbor cell’s layer HO threshold value will be the same. Same concept goes for the layer HO hysteresis. This can maintain the entire hierarchical layers of the cell.

16 9101112131415 12345678

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The 15th bit: Bit value is decided by cell type

• Serving cell or Neighbor cells:

• When cell type is extension cell 1.

• When cell type is normal cell 0.

The 16th bit: Reserved bit

16 9101112131415 12345678


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• General HO process• Measurement report preprocessing• Penalty processing• Basic ranking and secondary ranking • HO judgment


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HO Algorithm

Initializing

M rule

K rule

16bits rule

Emergency HO judgment

Load-HO judgment

Normal HO judgment

Fast moving HO judgmentLayer HO judgment

PBGT HO judgment

Send HO command

Send HO command

Send HO command

Overlaid/underlaid HO judgment

Edge HO judgment

Forced HO Direct re-tryO&M reason

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Types of HO

• Types of HO : Emergency HO

• TA & BQ HO, interference HO, Rx_Level_Drop HO Load HO Normal HO

• Edge HO, layer cell HO and PBGT HO Fast moving HO Overlaid/underlaid HO

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Emergency HO

• TA HO criterion : TA of the serving cell > TA Thrsh.

• BQ HO criterion : The average value of the uplink quality of the

serving cell >

UL Qual. Thrsh.

The average value of the downlink quality of the serving cell > DL Qual. Thrsh.

• Requirements on the target cell (same as the above two types of HO):

Select the first cell in the neighbor cell list i.e. lowest 16bits value.

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Emergency HO

• Rx_Level_Drop HO: Due to downlink signal level drop Triggered upon detecting rapid level drop during MS

busy mode.

• Requirements for the target cell: The target cell is the first cell in the neighbor cell list.

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Emergency HO

• Interference HO (DL&UL) : When the receiving level > receiving threshold

level. But Receiving quality < threshold of quality interference.

• Requirements for the target cell: The target cell is in the cell list.

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Cell Load HO

• Cell Load HO Criterions : System load of BSC < Permissible load of HO

threshold

Load of serving cell > Load HO threshold

• Requirements for the target cell Load of target cell < Load HO threshold

BTS

BSC

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Normal HO

• Edge HO Criterion: In N seconds, when there are P seconds that neighbor

cell’s DL or MS’s UL signal level is lower than the Edge HO threshold. Then the criterion is met and Edge HO occurs. This method utilizes the P/N rule.

• Requirements for the target cell: The target cell should be ranked in front of the serving

cell.

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Normal HO

• Layer HO criterions: Serving cell :

• No requirement.

Target cell :

• Layer of the target cell is lower than the serving cell.

• Receive level of the target cell > layer cell threshold + layer cell hysteresis.

• Target cell should be ranked in front of the serving cell. The priority of target cell should be higher than the serving cell’s.

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• PBGT HO Criterions : Target cell’s path loss is smaller than the serving

cell’s path loss by the PBGT threshold value.

Satisfying the P/N rule.

Target cell should be ranked in front of the serving cell.

• Note : PBGT HO can only occur between same-priority

cell. If the system permits PBGT HO for the cell, PBGT HO can occur in either inter-BSC or inter-MSC.

PBGT HO

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Fast-Moving HO

• When the serving cell is micro cell : When the MS has traveled through P numbers of

cell, and there are Q (=<P) numbers of cell that the MS has traveled in high speed, the criteria is satisfied. MS will be handed over to umbrella cell.

• When the serving cell is umbrella cell : When the MS is traveling high speed in umbrella

cell, a greater penalty can be given to the micro cell for a duration of time (penalty time). In this way, the MS will not use the micro cell. Note :In this case, the micro cell is only used under urgency conditions( Poor TA and BQ ).

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underlaid

overlaid

• Overlaid/underlaid : Division of underlaid and overlaid is decided by MS downlin

k receive level and TA value.

Overlaid/Underlaid HOOverlaid/Underlaid HO

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• Criterion for HO from overlaid to underlaid: TA value => TA threshold + TA hysteresis Or RX_LEV <= RX_LEV threshold － RX_LEV hysteresis Satisfying P/N rule

• Criterion for HO from underlaid to overlaid: TA value =< TA threshold － TA hysteresis and RX_LEV =< RX_LEV threshold + RX_LEV hysteresis Satisfying P/N rule

Overlaid/Underlaid HOOverlaid/Underlaid HO

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QuestionQuestion

• Can you list the function of each bit in 16bit ranking?

• What is the period of measurement report?

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Course Contents

49

Major HO Parameters Configuration

• Major HO parameter configuration 1.[Handover Control Table]

2.[Cell Description Table]

3.[Adjacent Cell Relation Table]

4.[Penalty Table]

5.[Emergency Handover Table]

6.[Load Handover Table]

7.[Normal Handover Table]

8.[Fast-Moving Handover Table]

9.[Concentric Cell Handover Table]

• HO data lookup process

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[Handover Control Table] -1Parameter

name Meaning Value range Recommen

ded value Co-BSC/MSC Adj.

It means whether the 12th and 13th bits acts in the 16bit order. “Yes” means handover in the same BSC/MSC is preferred. “No” means that the 12th and 13th bits are shielded and set to “0”.

Yes, No Yes

Penalty allowed

It determines whether to punish the target cell of handover failure, or the original served cell of handover upon too big TA or bad quality. The penalty measures can apply to cells in or out of the same BSC.

Yes, No No

Load HO allowed

It determines whether to perform the handover to share traffic load. Load sharing can lower the channel assignment failure ratio caused by cell congestion, so as to make evener allocation of the service in respective cells, and lower the cell congestion rate, and improve network performance. It only applies in the same BSC or cells at the same level.

Yes, No No

MS Fast moving HO allowed

It determines whether to handle the fast moving MS with the algorithm. It is only recommended in special areas (such as a highway), to lower CPU load. This algorithm should only be used in suitable conditions, and usually it is not applied.

Yes, No No

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[Handover Control Table] -2Parameter name Meaning Value range Recommended

value RX_Level_Drop HO allowed

It means whether RX_Level_Drop emergency handover algorithm is allowed, handover the MS which receiving signal level is dropping quickly in advance to avoid potential call drop. This algorithm should be applied in suitable conditions, and usually it is not used. To apply the handover algorithm, BSC must have original measurement report.

Yes, No No

PBGT HO allowed

It means whether PBGT handover algorithm is allowed. PBGT handover algorithm currently is processed on LAPD board. To avoid Ping-pang handover, PBGT handover is only performed between cells at the same layer and with the same priority, and meanwhile it is only triggered on TCH.

Yes, No Yes

MS power prediction after HO

It means after a handover whether MS is to use proper predicted transmitting power to access the new channel. This can reduce system interference and improve service quality (this parameter acts when intra BSC handover occurs).

Yes, No Yes

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Parameter name

Meaning Value range Recommended value

MR. Preprocessing

“Yes” means perform measurement report preprocessing on BTS; “No” means preprocessing on BSC, then the two parameters of “Send original measurement report” and “Send BS/MS power level” do not act. “Yes” means decreasing of Abis interface signaling and BSC load, and improving of network response time performance. The switch determines where to perform power control. When it is set to “Yes”, power control is performed at BTS side. When it is set to “No”, power control is performed at BSC side. When setting this parameter, first be clear whether BTS supports the power control algorithm to set or not.

Yes, No Yes

[Handover control table] -3

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Parameter name


Transfer original MR.

It means whether to send the original measurement report to BSC after measurement report preprocessing on BTS. When it is set to “Yes”, BTS sends not only processed measurement report but also original measurement report to BSC.

Yes, No No

Transfer BS/MS power class

It means whether to send BS/MS power level from BTS to BSC. This function is used to view the effect of power control on BTS. Meanwhile, when preprocessing is available, if BS/MS power level is not reported, the uplink and downlink balance measurements will be affected, and handover types such as PBGT handover and overlaid/underlaid handover needing power compensation will be abnormal.

Yes, No Yes


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Parameter name


Sent Freq. of preprocessed MR.

It indicates the time interval at which a measurement report is preprocessed at BTS side and sent to BSC the Preprocessed measurement report. This parameter acts only when “Measurement report pre-processing” is enabled. For 15:1 link configuration, the report frequency should be as low as once per second due to limited link resource. At this time, for handover needing P/N judgment such as edge handover, layer handover, PBGT handover and overlaid/underlaid handover,

Twice per second, Once per second

According to concrete conditions



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[Cell Description Table] -1

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[Cell Description Table] -2

57


[Adjacent Cell Relation Table] -1

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[Adjacent Cell Relation Table] -2


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[Penalty Table] -1


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[Penalty Table] -2


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[Emergency Handover Table] -1

Parameter name


TA Thrsh.

When TA≥this value, emergency handover is triggered

0~63 bit period

63

DL QUAL. Thrsh

The downlink receiving quality threshold for BQ emergency handover. When frequency hopping or DTX is enabled, RQ becomes worse (normal phenomenon), this value should be set to 70. The adjustment should also base on the current network quality and handover statistics. When triggering emergency handover, the first to select is the inter-cell handover, the intra-cell handover is only triggered when there is no candidate cell and the intra-cell handover is allowed in the serving cell.

0~70, corresponding to BQ levels of 0~7

60

UL QUAL. Thrsh.

The uplink receiving quality threshold for BQ emergency HO.

corresponding to BQ levels of 0~7

60


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63



64



65

[Load Handover Table] -1


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[Load Handover Table] -2


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[Normal Handover Table] -1Parameter

nameMeaning Value range Recommended value

Edge HO UL RX_LEV Thrsh.

During the statistics time, if the time in which the uplinkreceiving level is lower than the value is longer thancertain time called continuous time, edge handoverwill be performed. If PBGT handover is enabled,Corresponding edge handover threshold will be setlower.

0~63 25 (without PBGThandover, downtown),15 (single station onoutskirts), 15 (withPBGT handover,downtown)

Edge HO DLRX_LEV Thrsh.

Downlink consideration for edge HO. 63 30 (without PBGThandover, downtown),20 (single station onoutskirts), 20 (withPBGT handover,downtown)


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name Meaning Value range Recommended

value Edge HO watch time

It means that within the time statistics, if the time in which the signal level is lower than threshold is higher than the continuous time, then margin HO is to be triggered.

1~16 seconds 5

Edge valid time

See the above. 1~16 seconds 4


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[Normal Handover Table] -3

Parameter name


PBGT watch time

Statistics time for PBGT HO signal level judgment. 1~16 seconds 5

PBGT valid time

Continuous time for PBGT HO signal level judgment. 1~16 seconds 4


70


name Meaning Value range Recommended

value Layer HO watch time

Statistics time for Layer HO judgment 1~16 seconds 5

Layer HO valid time

Continuous time for Layer HO judgment. 1~16 seconds 4


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[Fast-Moving Handover Table]


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[Concentric Cell Handover Table] -1Paramete

r nameMeaning Value range Recommended

value

UO signal intensity difference

BTS transmitting Power difference between underlaid and overlaid may cause MS receiving signal intensity difference in underlaid and overlaid . The parameter uaually indicates the antenna EIRP difference in dB between underlaid cell and overlaid cell. According to field measurement, multi-point measurement is necessary if the underlaid and overlaid use different antenna.

0~63db Set according to actual conditions


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[Concentric Cell Handover Table] -2Paramete

r nameMeaning Value range Recommende

d value

RX_LEV Thrsh

Rx level hysteresis, TA threshold and TA hysteresis jointly define underlaid area and overlaid area. It must be bigger than edge handover threshold, and the recommended value is: edge handover threshold + signal intensity difference between underlaid and overlaid .

0~63 25

RX_LEV hysteresis

Works with Rx threshold. 0~63 5

TA Thrsh.

It must be bigger than TA emergency handover threshold.

0~63 bit period, with 1 bit period corresponding to 0.55km

TA hysteresis

Works with TA threshold. 0~63 bit period


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[Concentric Cell Handover Table] -3Parameter name Meaning Value

range Recommended

value UO HO watch time P/N judgment statistics time for U/O HO judgment. 0~16

seconds 5

UO HO valid time P/N judgment continuous time for U/O HO judgment. 0~16 seconds

4


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[Concentric Cell Handover Table] -4Parameter

nameMeaning Value range Recommended

value

Assign optimum layer

In Overlaid/Underlaid, the following selection are available for TCH assignment: (1) The system judges according to the measurement report on SDCCH and assign to the best sub-cell. (2) Select the overlaid first for TCH assignment. (3) Select the underlaid first for TCH assignment. (4) Do not give extra priority.

System optimization, overlaid , underlaid , no preferential

System optimization

Assign-optimum level Thrsh.

If system optimization is selected, estimate (interpolate, filter) current SDCCH level value through uplink measurement value in the former SDCCH measurement report, and compare with “ Assign-optimum Level threshold”, so as to assign overlaid or underlaid channel.If SDCCH is in the overlaid : edge handover threshold + signal intensity difference between underlaid and overlaid + uplink and downlink balance allowance + SDCCH and TCH difference allowance. If SDCCH is in the underlaid : edge handover threshold + uplink and downlink balance allowance + SDCCH and TCH difference allowance.

0~63


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[Concentric Cell Handover Table] -5

Parameter name

Meaning Value range

Recommended value

Pref. subcell in HO of intra-BSC

When the cell is configured into a Overlaid/Underlaid, there are two processing methods for incoming handover request in BSC: (1) No special processing for channel assignment. (2) Add BCCH signal level value of the target cell in inter-cell handover request message to BSC to make BSC allocate optimum channel for MS from underlaid or overlaid .

Yes, No Yes

Incoming-to-BSC HO optimum layer

If there is a incoming BSC HO, and the target cell is a Overlaid/Underlaid, then, this parameter will show which layer is preferred to provide service for the MS.

overlaid , underlaid , none

None


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HO Parameters Configuration

• HO data lookup process BA2 table defines BCCH frequencies of all

neighbor cells. It is sent to MS by system message 5, system message 5-bis and system message 5ter on SACCH channel.

MS reports the serving cell and BCCH, BSIC and signal levels of 6 strongest neighbor cells to BSS. This is done through SACCH.

MR pre-process is done in BTS. Module number, cell number and CGI of all neighbor cells are derived from Adjacent cell Relation Table, and Cell Description Table (or External Cell Description Table) through BCCH and BSIC in the MR.

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• HO data lookup process BSC performs HO judgment process, such as

basic rank of cells (completed in LAPD board). When BSC finds suitable target, It sends HO request messages containing the target CGI to MPU of BSC. According to CGI, MPU derive the module number of the cell from Cell Module Information Table.

MPU sends a HO command message to the target module and step up the ‘inter-cell/ intra-cell HO request’ counter by one.

Summary of BSC HO

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Course Contents

80


• Intra BSC Handover

• Intra MSC Handover

• Inter MSC Handover

81

Intra-BSC Handover Signaling process

MS MSBTS1 BTS2BSC MSC

Measurement Report from MS

Channel_Active

Channel_Active ACK

HANDOVER COMMAND

Handover Access

Handover_DetectPHY INFO

First SABMEstablish_IND

PHY INFO

Handover Complete

Handover_Performed

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• Attention In asynchronous HO, if MS could not reach the

new TCH channel after the target cell has sent PHY INFO up to max times, the target cell reports CONN FAIL IND to BSC with the reason: HO access failure.

After the above message is received, BSC release the assigned TCH channel in the target cell .

Max resend times of physical information*Radio link connection timer > Time interval between EST IND and HO DETECT (120~180ms). This is to make sure that the physical information reach MS.

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MS BTS BTSBSC MSCMeasurement Report

Measurement Report

Channel_Activate

Channel_Activate ACK

Handover Command (Old FACCH)

Handover Access (New FACCH)

Handover Complete (New FACCH)

RF Channel ReleaseHandover Performed

T09++T12++

T10++T13++

Attempted outgoing internal inter cell handovers

Attempted incoming internal inter cell handovers

Successful incoming internal inter cell handovers

Successful outgoing internal inter cell handovers

(Original) (Target)



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• Handover formula definition Internal inter cell radio handover success rate

=(Successful incoming internal inter cell handovers + Successful outgoing internal inter cell handovers) / (Incoming internal inter cell handovers + Outgoing internal inter cell handovers )

Internal inter cell handover success rate

=(Successful incoming internal inter cell handovers + Successful outgoing internal inter cell handovers) / (Attempted incoming internal inter cell handovers + Attempted outgoing internal inter cell handovers)

• Internal inter cell radio handover success rate >= Internal inter cell handover success rate

Measurement Points of Intra BSC Handover

85


• Intra BSC Handover

• Intra MSC Handover

• Inter MSC Handover

86

MS BTS BTSBSC1 BSC2MSC(original) (Target)

Measurement Report

Measurement ReportHandover Required

Handover Request

Channel_Active

Channel_Active_ACKHandover_Request_ACK

Handover Command

Handover Access

Handover Detect

Handover Complete

Handover Complete

Clear Command (HO Successful)

RF Channel ReleaseClear Complete

Attempted outgoing interBSC inter cell handovers

Attempted incoming interBSC inter cell handovers

Successful incoming inter BSC handovers

Successful outgoing interBSC inter cell handovers

Signaling intra MSC

Intra-MSC HO Signaling process

Intra-MSC HO Signaling process

88


• Intra BSC Handover• Intra MSC Handover• Inter MSC Handover

89

Signaling process between MSC

MSC-BMSC-A VLR-BBSC-A BSC-B

HO-REQUIRED MAP_Prepare_HO

MAP_Prepare_HO_ACK

MAP_Allocate_HO_NUM

MAP_Send_HO_Report

MAP_Send_HO_Report_ACK

MS

HO-REQUEST

HO-REQUEST-ACK

HO-Command

MS

HO-AccessMAP_Process_Access_Signalling

HO-CompleteMAP_Send_End_Signal

Clear-Command

Clear-Complete

MAP_Send_End_Signal_ACK

Some intermediate steps are omitted

IAIACM

Measurement Points of Inter-BSC Handover

90

Signaling process between MSC

MSC-BMSC-A VLR-BBSC-A BSC-B

HO-REQUIRED MAP_Prepare_HO

MAP_Prepare_HO_ACK

MAP_Allocate_HO_NUM

MAP_Send_HO_Report

MAP_Send_HO_Report_ACK

MS

HO-REQUEST

HO-REQUEST-ACK

HO-Command

MS

HO-AccessMAP_Process_Access_Signalling

HO-CompleteMAP_Send_End_Signal

Clear-Command

Clear-Complete

MAP_Send_End_Signal_ACK

Some intermediate steps are omitted

IAIACM

Measurement Points of Inter-BSC Handover

91

Inter-MSC HO Signaling process

• Signaling process – Abnormal conditions The following conditions will cause HO failure

• MSC-B fails to identify the target cell.• MSC-B does not allow HO to the indicated target ce

ll.• The target cell has no channel available.• VLR-B has no HO number available.• HO error or unsuitable data.

92

Roaming

E

MS

MSCa MSCbMSCb'

VLRbVLRb'

BSS2

BSS2'

Radio transmission signal measurementHO REQUIRED (target cell table)

Perform subsequent HO(MAP) (target cell ID, serving cell ID, MSC number)

Perform HO(target cell ID, serving cell ID, channel type)

HO REQUEST (PCM&Channel type)

HO REQUEST ACKNOWLmargin (including New TCH number and HO number)

Allocate HO number

Send HO report(HON)Radio channel ack. (MAP) (includes New TCH number and HON)

IAI

ACM

Subsequent HO ack.

HO COMMAND HO DETECT

HO COMPLETESend end signal (MAP)

ANS

End signal (MAP)Release HO report Release HON

CLEAR COMMAND

CLEAR COMPLETERelease (TUP)

Cut physical connection between MSCa and MSCb

End signal (MAP)

Release (TUP/ISUP)Release HO report Release HON

Cut physical connection between MSCAa and MSCb'

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MS

Inter MSC HO—Subsequent HO process

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Highway

MSC-AMSC-C

MSC-B MSC-C

Inter MSC HO—Subsequent HO process

• Subsequent HO

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Inter MSC HO Signaling process

• Statistics counter—same as Intra MSC HO, Statistics is handled by BSC

• HO formula-- same as Intra MSC HO

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Basic process of HO Signaling process

1. There is no “HO request” information for intra-BSC HO, and all of the HO are analyzed and processed in BSC. Once the target cell as required is found in the BSC, “Channel activation” information is sent to it directly.

2. When the target cell is not in the same BSC, BSC reports CGI numbers of the serving cell and target cell, and HO cause to MSC through “Ho-Required”. When MSC finds the LAC of the target cell is in the MSC, it sends “Ho-Request” to the BSC of the target cell, and the target BSC activates the target cell channel to complete the following procedure.

3. When MSC finds that the target cell LAC does not belong to the MSC, it will query its “LAI and GCI Table” (including LAC and router address of the adjacent MSC), and send “Prepare-HO” message to the target MSC-B according to the router address. The message includes CGI of the target cell and indication whether or not to allocate HO number, etc. According to the message, the target MSC-B sends “HO-Request” message to the target BSC-B after demanding HO number (unless it is not required in the indication) from VLR-B, and sends “Prepare-HO acknowledgement” to serving MSC after received “HO-Request acknowledgement”, to execute the next procedure.

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Intra-BSC HO and Inter-BSC HO

• Major differences: Inter BSC HO transfers “HO-REQ” message through

MSC, with CGI of the serving cell and target cell carried in the message.

Intra BSC HO does not have any CGI in any messages, it is handled inside BSC.

Intra BSC HO only sends “HO-Performed” to MSC upon completion of HO, and MSC is not involved before that time.

In inter BSC HO, MSC is involved since the HO request .

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Question

• What is the content of PHY INFO? When will the system send this message to MS?

• Why Internal inter cell radio handover success rate >= Internal inter cell handover success rate?

Thank You

Date post:	24-Nov-2014
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39034739-Handover-Training

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