25837798-EVOLIUM-Base-Station-Subsystem-Multilayer-GSM-Network[1].pdf

All rights reserved 2005, Alcatel

Multilayer GSM Network Radio Optimization / B9

EVOLIUM Base Station Subsystem

Multilayer GSM Network Radio Optimization / B9

TRAINING MANUAL

3FL12033ABAAWBZZAEdition 01 - January 2006

Copyright 2005 by Alcatel - All rights reservedPassing on and copying of this document, use and communication of its contents

not permitted without written authorization from Alcatel

All rights reserved 2005, AlcatelMultilayer GSM Network Radio Optimization / B9

2

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Product Line EVOLIUM Base Station Subsystem

Course Title Multilayer GSM Network Radio Optimization / B8

Course Reference 3FL 12033 ABAA - AUE

Audience

Radio Network Engineers (operator or Alcatel staff) in charge of optimizing a hierarchical network.

Objectives

During the course, the trainee will be able to describe the specific radio algorithms in multi-layer networks in order to enhance the offered QoS.

By the end of the course, the participant will be able to:

- Describe the concepts and strategy of hierarchical networks.

- Describe the specific type of cells implemented in hierarchical networks.

- Describe the specific radio algorithms used in the Alcatel BSS in a hierarchical network.

- Propose default parameter values for the cells of a hierarchical network using these algorithms.

- Propose a list of specific indicators to monitor QoS and traffic in a hierarchical network.

Note: Radio Network Planning issues like micro site detection, site planning, frequency planning are not included.

Prerequisites

Training module Introduction to GSM QoS and Traffic Load Monitoring (3FL 10491 ABAAAUE) and Introduction to Radio Fine Tuning (3FL 10493 ABAAAUE) or equivalent level.

Training Methods

Theory / Practice.

Language

English, French

Duration

3 Days

Location

Alcatel University or Customer Premises.

Number of participants

Maximum 8

Course content

1 Multi-layer Network Architecture

1.1 Concepts and strategies

1.2 Cellular network architecture

1.3 Choosing a relevant architecture

1.4 Requirements

2 Algorithms and Associated Parameters

2.1 Introduction

2.2 Idle mode selection and reselection

2.3 Call setup

2.4 Handover strategies

2.5 Main standard handover algorithms

2.6 HO algorithms for multi-layer networks

2.7 Candidate cells evaluation

3 Creating a Multi-layer Network

3.1 Adding a micro cellular layer in an existing network for traffic and coverage increase

3.2 Adding hot spot microcells for traffic

3.3 Adding indoor microcells for coverage

3.4 Monitoring QoS in a multi-layer network

4 Case studies

4.1 Radar cell

4.2 Symmetric microcells at street corner

4.3 Asymmetric microcells at street corner

4.4 Indoor microcell within a monolayer network

4.5 Trilayer network: indoor cell within a multi-layer network

4.6 Indoor cell congestion

4.7 Transforming a microcell into an indoor cell

4.8 Picocells in skyscrapers


4

Table of Contents [cont.]

Switch to notes view!

This page is left blank intentionally


5

1 MULTI-LAYER NETWORK ARCHITECTURE


6


Session presentation

Objective: to be able to define relevant architectures for

multi-layer networks design

Program:




1.4 Requirements


7




8

Multi-layer network: a powerful solution for:

Network capacity enhancement

extra capacity provided by new cells / new TRXs

specific radio algorithms send MSs to these new cells

Coverage increase

when introducing microcells (better indoor penetration, even for outdoor

microcells)

While keeping a good QoS

confined coverage for microcells, with less interference

less congestion


Introduction to multi-layer networks

Since B7:

new HW capabilities with Cell split support

enhancement of QoS monitoring capabilities with counters split per TRX


9

Alcatel is providing multi-layer solutions

Since R3.1: mini & microcells

Improvements in B3.1 (smart speed discrimination)

Improvements in B6.2 (external Directed Retry)

Improvements in B7 (indoor layer introduction)


Support of multi-layer features


10

Multi-layer networks can be introduced as continuous layer or hotspots, for:

Capacity increase

Coverage increase

Indoor solution

All types of mobiles can use both layers


Network strategy

If the speed discrimination process is activated then Phase 2 MSs will be sent more or less quickly according to the

load of the umbrella cell.


11




12

Conventional

Single cell

Concentric cell

Extended cell

Multi-band cell

Hierarchical: introducing Upper and Lower cell layers

Indoor cell

Micro cell

Mini cell

Umbrella cell


Cell environment


13

One unique combination of the five parameters

CELL_DIMENSION_TYPE: macro, micro

CELL _LAYER_ TYPE : single, upper, lower, indoor

CELL _PARTITION_ TYPE : normal, concentric

CELL _RANGE: normal, extended inner, extended outer

FREQUENCY_RANGE : PGSM(GSM900); DCS1800; EGSM;

DCS1900; PGSM-DCS1800; EGSM-DCS1800 and GSM 850

based on BCCH frequency


Cell profile


14


Mono-band Cell profiles

DCS1800 or DCS1900DCSNormalNormalIndoorMicroDCS indoor micro cell

PGSM or EGSMGSMNormalNormalIndoorMicroGSM indoor micro cell

DCS1800 or DCS1900DCSNormalConcentricUpperMacroDCS concentric umbrella

PGSM or EGSMGSMNormalConcentricUpperMacroGSM concentric umbrella

DCS1800 or DCS1900DCSNormalConcentricSingleMacroDCS concentric cell

PGSM or EGSMGSMNormalConcentricSingleMacroGSM concentric cell

DCS1800 or DCS1900DCSExtended-outerNormalSingleMacroDCS extended outer cell

PGSM or EGSMGSMExtended-outerNormalSingleMacroGSM extended outer cell

DCS1800 or DCS1900DCSExtended-innerNormalSingleMacroDCS extended inner cell

PGSM or EGSMGSMExtended-innerNormalSingleMacroGSM extended inner cell

DCS1800 or DCS1900DCSNormalNormalUpperMacroDCS umbrella cell

PGSM or EGSMGSMNormalNormalUpperMacroGSM umbrella cell

DCS1800 or DCS1900DCSNormalNormalLowerMacroDCS mini cell

PGSM or EGSMGSMNormalNormalLowerMacroGSM mini cell

DCS1800 or DCS1900DCSNormalNormalLowerMicroDCS micro cell

PGSM or EGSMGSMNormalNormalLowerMicroGSM micro cell

DCS1800 or DCS1900DCSNormalNormalSingleMacroDCS single cell

PGSM or EGSMGSMNormalNormalSingleMacroGSM single cell

Frequency rangeCell band

type

Cell

range

Cell partition

type

Cell layer

type

Cell dimension

type

Parameters

Cell Profile


15


Multi-band Cell profiles

PGSM-DCS1800 or

EGSM-DCS1800DCSNormalConcentricIndoorMicroDCS multiband indoor micro cell

PGSM-DCS1800 or

EGSM-DCS1800GSMNormalConcentricIndoorMicroGSM multiband indoor micro cell

PGSM-DCS1800 or

EGSM-DCS1800DCSNormalConcentricUpperMacroDCS multiband umbrella cell

PGSM-DCS1800 or

EGSM-DCS1800GSMNormalConcentricUpperMacroGSM multiband umbrella cell

PGSM-DCS1800 or

EGSM-DCS1800DCSNormalConcentricLowerMacroDCS multiband mini cell

PGSM-DCS1800 or

EGSM-DCS1800GSMNormalConcentricLowerMacroGSM multiband mini cell

PGSM-DCS1800 or

EGSM-DCS1800DCSNormalConcentricLowerMicroDCS multiband micro cell

PGSM-DCS1800 or

EGSM-DCS1800GSMNormalConcentricLowerMicroGSM multiband micro cell

PGSM-DCS1800 or

EGSM-DCS1800DCSNormalConcentricSingleMacroDCS multiband single cell

PGSM-DCS1800 or

EGSM-DCS1800GSMNormalConcentricSingleMacroGSM multiband single cell

Frequency rangeCell band typeCell

rangeCell partition typeCell layer typeCell dimension type

Parameters

Cell Profile


16


Cell profiles: example


17




18

Multi-layer concept: 3 available layer types

All these cells can be or not operating in the same band and defined as

concentric cells


Concept

mini

umbrella

micro

indoor

micro micro

umbrella

micro

indoor

single

mini

umbrellaUPPER

SINGLE

LOWER

INDOOR

3 layers are defined in the system, but more layers can be created by parameter tuning. For example, skyscrapers

specific configuration is made up of several consecutive layers designed with cells of the same system layer.

Indoor layer has been introduced in B7.


19

Microcells configuration will depend on their position in the lower layer

Microcell classes are introduced to deal with typical parameters settings

in each of these cases


Microcell classes

Indoor Microcell

Border Microcell

Inner MicrocellHotspot Microcell

Defining microcell classes is a very efficient way to set network parameters. It avoids defining a specific configuration

for each cell.


20


1.4 Requirements


21

A multi-layer architecture can be built over all types of Hardware

Since R3.1

Microcell feature is NOT reserved to micro BTS!

Improvement in B6.2 with external Directed Retry

From R3.1 to B4.1, since Directed Retry was only Internal:

microcells had to be introduced within umbrella BSC

OR microcells were barred (traffic allocation was done by handover from

umbrella cells)

Since B6.2, External Directed Retry is available

Microcells and Umbrella cells can belong to different BSCs

1.4 Requirements

Software & Hardware requirements


22

2 ALGORITHMS AND ASSOCIATED PARAMETERS


23


Session presentation

Objective: to be able to describe algorithms dedicated to

multi-layer networks management

Program:

2.1 Introduction


2.3 Call setup



2.6 Handover algorithms for multi-layer networks

2.7 Candidate cell evaluation


24


2.1 Introduction


25

With the introduction of new feature and algorithms:

Multi-layer

Designing, managing and monitoring complex networks is more difficult,

as all these features will interact

An in-depth knowledge of all available algorithms is necessary to understand

all possibilities and difficulties. A relevant choice of architecture and

parameters settings will precede the introduction of a new layer in the existing

network

2.1 Introduction

Justification


26

In all this document

System parameters (can be set at the OMC-R level) will always be written in

BLUE BOLD FONT

Variables (averages, internal system variables, etc.) will be typed in NORMAL

FONT

Light blue font highlights important points

2.1 Introduction

Typing conventions


27




28

Adding a new layer is a powerful way of increasing network capacity if

the MS can be sent to the preferred cell

In dedicated mode: see next sections

But also in idle mode, so that the call is established directly in the preferred

cell

Really increase capacity

Maintain high QoS level, without creating extra HO


Strategy


29

At startup (IMSI Attach), the MS is selecting cell with

Defined priorities with CELL_BAR_QUALIFY

Best C1 amongst highest priority cells (using CBQ)

Once camped on one cell (in idle mode)

The MS can decide to reselect another one if:

C1 criterion 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 criterion


Selection and reselection principles

Note:

Cell selection (first selection) is performed using C1 criterion only (the chosen cell is the one with the best C1)

Reselection is done using the mechanisms referenced above.

e.g., the MS cannot access the cell.

It can be linked to SDCCH congestion, filtering of CHARQD due to TA greater than RACH_TA_FILTER, radio access

problem during the Radio Link Establishment phase.

If SDCCH is to be seized for LU purpose, the MS will reselect on another cell.

If SDCCH is seized for something else (e.g., MOC), the MS may reselect (this is up to the MS vendor

choice!!!). Some MSs do nothing. Call will never be possible. Some others do reselect. In that case, the user

has to reattempt his call (after the reselection, but before the MS is back to the original cell due to better C2,

etc. (done after 5 s, etc.)).


30

Cell selection, use of CELL_BAR_QUALIFY:

set on a per cell basis

broadcast on the BCCH

2 possible values:

0 = normal priority (default value)

1 = lower priority

The MS selects the suitable (C1 > 0) cell with the highest C1 belonging to the

list of highest priority


Cell Selection with CBQ (1/3)


31

Example: highest priority set on microcell

The MS will select the microcell (if available, C1>0), whatever the level of the

macrocell



2525microcell

CELL_BAR_QUALIFY = 0

2020

macrocell

CELL_BAR_QUALIFY = 1


32

WARNING: usage of CELL_BAR_QUALIFY:

interacts with CELL_BAR_ACCESS

A cell with low priority (CELL_BAR_QUALIFY = 1) cannot be barred

Some MSs will be able to access it, whatever the value of CELL_BAR_ACCESS




33

C1

ensures that, if a call was attempted, it would be done with a sufficient

downlink and uplink received level

based on 2 parameters, broadcast on the BCCH

RXLEV_ACCESS_MIN [dBm]

- Minimum level to access the cell- Default value (for Evolium): -103 dBm

MS_TXPWR_MAX_CCH [dBm]

- Maximum level for MS emitting- Default value: 33 dBm


C1 criterion (1/2)


34

C1

evaluated every 5 s (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


C1 criteria (2/2)


35

C2 If 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 a 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 comparison with C2

C2neighboring > C2current if cells belong to the same LA

C2neighboring > C2current+CELL_RESELECT_HYSTERESIS if cells from

different LA


C2 criterion

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 neighboring cells. To penalize a cell

compared to one neighboring cell, one should better boost the neighboring cell (using first formula).

The first formula is very useful to favor an indoor cell or a microcell.


36

CELL_RESELECT_PARAM_IND C2 parameters are broadcast if = 1 (default)

otherwise C2 = C1

PENALTY_TIME

0 to 31, =20s + 20s step, default value = 0

From 0=20s to 30=620 s, plus 31: infinite penalty

CELL_RESELECT_OFFSET

0 to 63, 2 dB step, default value = 0

From 0 dB to 126 dB

TEMPORARY_OFFSET

0 to 7, 10 dB step, default value = 0

From 0 dB to 60 dB, plus 7: infinite dB


C2 parameters


37


Application

MINIMINI

MINI 900

CELL_RESELECT_OFFSET = 20

dB

TEMPORARY_OFFSET = 0 dB

PENALTY_TIME = 0 (20 s)UMBUMB

UMBRELLA 900

CELL_RESELECT_OFFSET = 0 dB

TEMPORARY_OFFSET = 0 dB

PENALTY_TIME = 0 (20 s)

C2(MINI) = C1(MINI) + 20

C2(900) = C1(900)

=> the reselection of the mini cell is favored


38


2.3 Call setup


39

Call setup is to be made on the cell selected in idle mode

Priorities have been defined with idle mode parameters

MSs are sent to the preferred cell

Lower layers

What is the risk??

2.3 Call setup

Principles


40

The risk is to have congestion in the preferred cell!

Old cells (old layer capacity) are unloaded

as all MSs are sent to new cells

This phenomenon is amplified by handovers behavior

Dual layer algorithms are based on CAPTURE mechanisms

Send the MS in the preferred cell as soon as it is OK

Without comparing serving and preferred cells

to reach the maximum capacity increase

See handover parts for details

2.3 Call setup

Congestion in the preferred cell


41

2.3 Call setup

Algorithms principles (1/3)

new

capacity

Traffic

increase

old

capacity


42

2.3 Call setup


new

capacity

Water Valve with filter:

Dual layer algorithms

Traffic

increase

old

capacity


43

2.3 Call setup


new

capacity

Water Pump:

Forced

Directed Retry

Traffic

increase

old

capacity


44

A Directed Retry:

Is an SDCCH to TCH intercell handover

Is triggered during a 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 a 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)

2.3 Call setup

Directed Retry principles


45

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 (intracell HO))

candidate cell evaluation process: same as for TCH HO

2.3 Call setup

Directed Retry


46

CAUSE 20: Forced Directed Retry

AV_RXLEV_NCELL_DR(n) > L_RXLEV_NCELL_DR(n)

And EN_FORCED_DR = ENABLED

EN_FORCED_DR value is only relevant if EN_DR = true

AV_RXLEV_NCELL_DR(n) is calculated with the A_PBGT_DR window

if less than A_PBGT_DR samples are available, the average value is

calculated with the available samples and the averaging window is filled in

with -110 dBm

2.3 Call setup

Forced Directed Retry: cause 20


47

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)

The remaining cells are sorted according to 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)

2.3 Call setup

FDR: Candidate cell evaluation


48

L_RXLEV_NCELL_DR(n): level required in the neighboring cell n

The parameter considered is the one set in the neighboring cell

The default value depends on the network architecture

See the next slide

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

neighboring cell n

The parameter considered is the one set in the neighboring cell

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

A_PBGT_DR: average window

Default value = 4 SACCHs

2.3 Call setup

FDR: parameters


49

DR on usual HO alarms does not create any radio problems as mobiles

remain within the service area of the new serving cell

Forced DR can introduce severe interference problems because MSs

are outside the cell normal service area

Forced directed retry between one

micro cell and its umbrella macro cell

OK: same service area

Simple parameters settings

Forced directed retry between 2

micro or macro cells

according to the frequency plan

2.3 Call setup

Managing DR parameters

Umbrella cell

microcell

FDRcapture


50

Thanks to idle mode parameters, Access to one preferred cell

Micro / Indoor layer: layer with very good QoS

For a better capacity increase and to avoid QoS degradation that may be

induced by an increase in HO attempts

Prevention of congestion in the preferred cell Forced Directed Retry to the old cells

Prevention of congestion in the old cells MSs are sent in idle mode to the preferred cell

HO strategy favoring the preferred cell in dedicated mode

2.3 Call setup

Access strategy


51

2.3 Call Setup

Exercise

Time allowed:

10 minutes

A dual layer network is considered

Umbrella cells 900

Micro cells 900

Set FDR parameters to avoid interference and allow

a powerful TCH resource usage

Umbrella cells

microcells

FDRcapture


52




53

Maximizing capacity

Intelligent MS sharing between available resources

Avoid congestion of historical band (for old MS)

Consider traffic conditions of all layers

Consider MS speed for layer discrimination

Keep mobiles in the same layer as long as possible


Objectives (1/2)


54

Assuring good quality communications and avoiding call drops

Send MS towards the layer that will provide the best QoS

Minimize the number of HO between cells for good speech Quality

Fast moving mobiles are handled by the macrocell layer

Identify a best target for emergency handovers cases

The tuning of the parameters will result in trade-offs


Objectives (2/2)


55

Next parts will detail available HO causes for multi-layer network

management

Mainly, HO performed between cells of the same layer are the same as for

standard networks

New handover causes are mandatory to manage HO between cells of

Different layers


Handover algorithms


56


Functional Entities

Radio

Link

Measurements

Active

Channel

Pre-processing

Assignment of HO functions in the ALCATEL BSS

BTS BSC

HO DetectionHO Candidate

Cell Evaluation

HO

management

MSC

HO

protocol


57

HO causes for standard networks

cause 2 : too low quality on the uplink

cause 3 : too low level on the uplink

cause 4 : too low quality on the downlink

cause 5 : too low level on the downlink

cause 6 : too large distance between the MS and the BTS

cause 15 : high interference on the uplink (intra-cell HO)

cause 16 : high interference on the downlink (intra-cell HO)

cause 26 : AMR channel adaptation HO (HR to FR)

cause 12 : power budget evaluation

cause 23 : traffic

cause 27 : AMR channel adaptation HO (FR to HR)

cause 28 : Fast traffic HO

cause 29 : TFO HO

cause 20 : FDR


Handover causes (1/2)


58

HO causes for multi-layer networks

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

cause 14 : high level in the neighboring cell of a lower or indoor layer for

slow mobile

cause 24 : general capture


Handover causes (2/2)


59

cause 7 : consecutive bad SACCH frames received in a microcell cause 17 : too low level on the uplink in a cell compared to a high threshold cause 18 : too low level on the downlink in a cell compared to a high threshold cause 2 : too low quality on the uplink cause 3 : too low level on the uplink cause 4 : too low quality on the downlink cause 5 : too low level on the downlink cause 6 : too large distance between the MS and the BTS cause 10 : too low level on the uplink in the inner zone cause 11 : too low level on the downlink the in inner zone cause 26 : AMR channel adaptation HO (HR to FR) cause 15 : high interference on the uplink (intra-cell HO) cause 16 : high interference on the downlink (intra-cell HO) cause 21 : high level in the neighboring cell in the preferred band

cause 14 : high level in neighboring cell of a lower or an indoor layer cell for slow mobile

cause 24 : general capturecause 12 : power budget evaluationcause 23 : traffic

cause 13 : too high level on the uplink and downlink in the outer zone cause 27 : AMR channel adaptation HO (FR to HR) cause 20 : Forced Directed Retry DR cause 28 : Fast traffic HO


Handover causes priority


60




61

Emergency intercell handovers

cause 2 : too low quality on the uplink

cause 3 : too low level on the uplink

cause 4 : too low quality on the downlink

cause 5 : too low level on the downlink

cause 6 : too large distance between the MS and the BTS

May be triggered

From any cell type / band / layer / zone

Towards any cell except the serving one


Emergency Intercell Handovers


62

CAUSE 2: too low quality on the uplink

AV_RXQUAL_UL_HO > L_RXQUAL_UL_H + OFFSET_RXQUAL_FH

and AV_RXLEV_UL_HO


63

CAUSE 3: too low level on the uplink

AV_RXQUAL_UL_HO


64


Handover Cause 4: DL Quality

CAUSE 4: too low quality on the downlink

AV_RXQUAL_DL_HO > L_RXQUAL_DL_H + OFFSET_RXQUAL_FH

and AV_RXLEV_DL_HO


65


Handover Cause 5: DL Level

QUAL

LEV

CAUSE 5: too low level on the downlink

AV_RXQUAL_UL_HO


66


Handover Cause 6: Distance

CAUSE 6 : Too long distance

AV_RANGE_HO > U_TIME_ADVANCE

and EN_DIST_HO = ENABLED

Size of window for distance average: A_RANGE_HO

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. 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. For these reasons also, this cause does not wait for

the power control to react.


67

Emergency intracell handovers

cause 15 : high interference on the uplink (intra-cell HO)

cause 16 : high interference on the downlink (intra-cell HO)

May be triggered

From any cell type / band / layer / zone

Towards the same cell


Emergency Intracell Handovers


68

CAUSE 15: High interference on the uplink

Intra-cell HO

AV_RXQUAL_UL_HO > THR_RXQUAL_CAUSE_15 +

OFFSET_RXQUAL_FH

and AV_RXLEV_UL_HO > RXLEV_UL_IH

and EN_CAUSE_15 = ENABLED

and [ no previous intracell handover for this connection

failed

or EN_INTRACELL_REPEATED = ENABLED ]

Size of window for averaging quality: A_QUAL_HO

Size of window for averaging level: A_LEV_HO


Handover Cause 15: UL Interference

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


69

CAUSE 16: High interference on the downlink

Intra-cell 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 = ENABLED ]

Size of window for averaging quality: A_QUAL_HO

Size of window for averaging level: A_LEV_HO


Handover Cause 16: DL Interference

THR_RXQUAL_CAUSE_16 and EN_CAUSE_16 are not parameters but variables defined after.


70


New 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 = DISABLED, when a HO CAUSE 15 (or 16) fails, it can be modified

as UPLINK (or DOWLINK) QUALITY, HO CAUSE 2 (respectively HO CAUSE 4).


71

CAUSE 12: Power budget

Normal handover type, no matter of emergency

Checked between

Cells of the same layer only

Specific case of Fast MSs: after detection of cause 12 in the lower or indoor layer,

they can execute cause 12 HO towards the upper layer

Cells may be of different cell_band_type, depending on parameter

EN_MULTIBAND_PBGT_HO

if EN_MULTIBAND_PBGT_HO = DISABLED and if the MS is located in the inner

zone of a multi-band cell, it can only go to another multi-band cell


Handover Cause 12: Power Budget (1/5)


72

CAUSE 12:

Based on 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)

Size of window for level averaging: A_PBGT_HO



The value of PBGT(n) is calculated every SACCH period for each neighboring cell n whose measures are kept in the

book-keeping list


73


if EN_TRAFFIC_HO(0,n)=ENABLED

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

+ max(0, DELTA_HO_MARGIN(0,n))

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

and AV_RXLEV_PBGT_HO RXLEV_LIMIT_PBGT_HO

and EN_PBGT_HO = ENABLED

Size of window for level averaging: A_PBGT_HO



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

cause 23 HO (EN_TRAFFIC_HO).


74


DELTA_HO_MARGIN(0,n): evaluated according to the traffic situation of the

serving cell and the neighboring 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.



HIGH LOW


75


Traffic_load() is managed for every cell of a BSC

Traffic_load() can have three values:

HIGH: cell is loaded

LOW: cell is unloaded

INDEFINITE: cell load is neither loaded nor unloaded, or unknown

The 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 modified (5 s)



Annex 1

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


76

HO_MARGIN(0,n)

A high value is usually used to avoid ping-pong HO in urban environment

where signal strength varies rapidly due to fading

Default value: site dependent (but 10 dB observed for dense urban microcellular

area)

To be optimized: can be reduced to 5dB and even 0 dB when applying an anti ping-

pong mechanism

A_PBGT_HO

To find a compromise with HO_MARGIN(0,n)

Default value: 8 SACCHs for urban microcells, 6 for dense urban


Cause 12: tuning of microcells parameters


77

HO_MARGIN(0,n) optimization

Not triggering too many HOs (ping-

pong)

Not triggering HO to a bad

target cell (for example, the

perpendicular cell at a crossroads)

Not favoring emergency HO (towards the

umbrella cell) with respect to power budget HO

between 2 micro cells (for example when turning

at a street corner)



Micro 1Micro 2

Micro 3

PBGT HO between micro cells 1, 2


78

HO_MARGIN(0,n) optimization

A high value of HO_MARGIN(0,n)

will delay the HO, thus it may

create interference problems in

case of adjacent frequencies

between 2 neighboring microcells

If HO_MARGIN(0,n) is reduced

(5dB or 0 dB), it allows adjacent

frequencies between neighboring

microcells, BUT the average

window should be increased to

reduce ping-pong HO risks or the

anti ping-pong mechanism should

be applied.



BTS1

BTS2

Building

Interferer

fn

fn+1

Area of potential interferences: (C/I)adj < -

9dB


79

Transfer of fast MSs from lower or indoor layers to upper layer

If EN_SPEED_DISC = ENABLED


Cause 12: speed discrimination in microcells (1/2)

Traffic Load = low Traffic Load low

HOHO HO HO

HO

MIN_CONNECT_TIME


80

Speed discrimination process in micro cells:

speed estimation based on the connection time in the cell

speed is estimated from the last handover from another microcell

if this connect time is below MIN_CONNECT_TIME, MS_SPEED is set to

FAST. Consequently the MS will be sent to an unloaded umbrella cell.

C_DWELL is a counter measuring the number of SACCH periods of monitoring

serving micro cell

if the call has been established after an intra-BSC handover from another micro cell

then C_DWELL is compared to the threshold 2*MIN_CONNECT_TIME in order to

determine MS speed

if C_DWELL < 2*MIN_CONNECT_TIME then MS_SPEED is set to FAST

MIN_CONNECT_TIME is not modified according to the load of the micro or

umbrella cells


Cause 12: speed discrimination in microcells (2/2)

Initialization of C_DWELL in serving micro cells

after call setup or incoming inter-cell handover

C_DWELL = 0

after intra-cell handover

C_DWELL is unchanged


81


Handover Cause 23: Traffic (1/2)

CAUSE 23: Traffic Handover

The aim of this cause is to speed HO detection when

The serving cell is loaded

The target cell is unloaded

When traffic distribution is taken into account for handover detection,

this cause reacts in the opposite way of cause 12, to maintain an

equivalent ping-pong static hysteresis

Checked between

Cells of the same layer only

If EN_MULTIBAND_PBGT_HO = disabled

Cells of the same cell_band_type only

if the MS is located in the inner zone of a multi-band cell, it can only go to

another multi-band cell

Else any other cells whatever their cell_band_type

HIGH LOW

In some multi-band networks, the radio coverage is ensured by DCS cells in one geographical area and by GSM cells

in another geographical area. As these cells form a multi-band and mono-layer network, the capture handovers

between cells of different bands will be inefficient to regulate the CS traffic load in the serving cell neighboringhood.

The solution consists in allowing intra-layer traffic handovers (Cause 23) based on a power budget evaluation

between cells of different bands.


82


Handover Cause 23: Traffic (2/2)

CAUSE 23: Traffic Handover

DELTA_HO_MARGIN(0,n) < 0 dB

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

+ DELTA_HO_MARGIN(0,n)

and EN_TRAFFIC_HO(0,n) = ENABLED

Size of window for level average: 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 neighboring 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

neighboring cells 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

neighboring cells without any cell frequency band restriction.


83


Handover Cause 28: Fast Traffic HO (1/3)

CAUSE 28: Fast Traffic Handover Push out of a cell a mobile in dedicated mode to allow a queued request

to be served in the serving cell

May be triggered From any non concentric cell OR concentric outer zone


HO

New call attempt Most appropriate MS to be pushed out

Congested cell

New call attempt

HO

Most appropriate MS

to be pushed out

Upper Layer Cell


84



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

FR (whatever the TRX

type)FR

HR

or

FR on dual rate TRX

HR

Candidate MSQueued Request


85



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_FAST_TRAFFIC_HO = ENABLED

Size of window for averaging level: A_PBGT_DR

Same thresholds and window as Cause 20 (FDR)

EN_CAUSE_28 is an internal HOP process variable, ENABLED when a

request is queued

HO cause 28 process:

If EN_FAST_TRAFFIC_HO = enabled, 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=enabled).

Once an HO alarm for cause 28 is triggered, the flag EN_CAUSE_28 is set to disabled 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 it is so, RAM asks HOP 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.


86


Exercise (1/2)

Detection of cause 12

Parameters settings

No Power Control DL, no anti ping-pong

EN_PBGT_HO = enabled

EN_TRAFFIC_HO(0,n) = disabled

HO_MARGIN(0,n) = 5 dB

RXLEV_LIMIT_PBGT_HO = -47 dBm

In each case, determine if cause 12 is detected or not

Time allowed:

15 minutes


87

Is cause 12 triggered?


Exercise (2/2)

9009001800900Band

FastFastSlowIndMS speed

Cause 12 ?

PBGT ?

-80 dBm-65 dBm- 65 dBm-80 dBmRx_Lev(n)

HIGHLOWLOWINDTraffic(n)

MicroUmbrellaUmbrellaSingleType

Target

-90 dBm-90 dBm- 90 dBm-85 dBmRx_Lev(0)

NoYesYesNoEN_SPEED_DISC

900900900900Band

MiniMicroMicroSingleType

Source

Case 4Case 3Case 2Case 1Inputs


88




89

An MS is located in a lower or an indoor layer of a hierarchical network

A problem is detected on the radio link between the MS and the BTS,

this problem is reported with an alarm cause:

Identical to standard networks

cause UL or DL quality (cause 2 and 4)

cause UL or DL Level - Low threshold (cause 3 and 5)

cause Distance (cause 6)

Specific to microcells or indoor cells

cause UL or DL for Microcell - High threshold (cause 17 and 18)

cause consecutive bad SACCH frames (cause 7)


Emergency handovers: introduction (1/2)


90

An MS is located in a micro or an indoor cell

During an emergency HO, the MS is directed preferably towards an upper or

a single cell

An MS is located in a mini cell

During an emergency HO, the MS is directed preferably towards neighboring

mini cells


Emergency handovers: introduction (2/2)

in

umbrella

mini

umbrella

mini

single


91

Emergency handovers specific to microcells

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

May be triggered

From microcells only (cell_dimension_type = micro)

Outdoor microcell (micro layer)

Indoor microcell (indoor layer)


If the MS is connected to the inner zone of a multi-band cell, the serving cell

is a candidate


Emergency Handovers specific to microcells


92

CAUSE 7: consecutive bad SACCH frames received in a microcell

Last N_BAD_SACCH frames received are not correct

and EN_MCHO_RESCUE = ENABLED

N_BAD_SACCH

Default value: 4 SACCHs

Rule:

N_BAD_SACCH > RADIOLINK_TIMEOUT_BS - N_BSTXPWR_M

to be sure that Radio Link Recovery in the microcell will be triggered before trying to

make a handover towards the umbrella

RADIOLINK_TIMEOUT_BS = 18 SACCH

N_BSTPWR_M = 15 SACCH


Cause 7: consecutive bad SACCH frames received in a microcell


93

CAUSE 17: too low level on the UL in a microcell compared to a high

threshold

AV_RXLEV_UL_MCHO(i) U_RXLEV_UL_MCHO

and EN_MCHO_H_UL = ENABLED

Averaging window: A_LEV_MCHO


Cause 17: too low level on the UL in a cell compared to high thr.


94

CAUSE 18: too low level on the DL in a microcell compared to a high

threshold

AV_RXLEV_DL_MCHO(i) U_RXLEV_DL_MCHO

and EN_MCHO_H_DL = ENABLED

Averaging window: A_LEV_MCHO


Cause 18: too low level on the DL in a cell compared to high thr.


95

High threshold (U_RXLEV_XX_MCHO)

the HO is triggered when the signal drops under the threshold

the corresponding HO causes consist in comparing, at 2 successive SACCH periods, the

DL and UL levels in the serving microcell with a high threshold

Beginning a call under the threshold does not trigger an HO


Cause 17 & 18: comparison to high threshold (1/4)

ii-1

t

AV_RXLEV_XX_MCHO

High

Threshold

HO alarm

ii-1

t

AV_RXLEV_XX_MCHO

High

Threshold

no HO alarm


96

High threshold (U_RXLEV_XX_MCHO)

With high value, mobiles will be sent too early to the macro layer

With low value, mobiles turning at a street corner will be maintained in the

microcell layer during a longer period

In theory, there is risk of call drop

In practice, with appropriate parameters,

- A PBGT HO should be triggered before (speed < 40 km/h)

- Low Threshold for safety

Problems of indoor mobiles with a signal strength level close to the high

threshold that should be kept as long as possible in the micro-layer




97

U_RXLEV_XX_MCHO compared to L_RXLEV_XX_H

typical gap taken: 2dB

for DL:

L_RXLEV_DL_H = -93 dBm

U_RXLEV_DL_MCHO = -91 dBm

for UL:

L_RXLEV_UL_H = -95 (M2M), -98 (M4M), -102 (Evolium) dBm

U_RXLEV_UL_MCHO = -93 (M2M), -96 (M4M), -100 (Evolium) dBm




98

A_LEV_MCHO

The averaging window size shouldnt be too small in order to:

avoid triggering too easily an HO on fading and overloading needlessly the macrocell

favor as much as possible between 2 micro cells PBGT HO

Typical value: 10 SACCHs

The high threshold is used to modelize a slow decrease of the signal level at microcell

border

Really urgent handovers will be triggered using the Low Threshold (cause 3 & 5) with a

short averaging window size

A_LEV_HO

Default value: 6 SACCHs for urban micro cells, 4 for dense urban ones




99

CAUSE 14: high level in a neighboring cell of a lower or an indoor layer

for slow mobiles

historical capture handover

Introduced in R3

Improved in B4 (enhanced speed disc.)

Improved in B4.1 (dual band MS support)

Improved in B7 (indoor & anti ping-pong)

May be triggered

From upper layer cells

Towards lower or indoor layer cells

From lower layer cells

Towards indoor layer cells


Cause 14: high level in a lower or an indoor layer for slow MSs (1/4)

mini

umbrella

micro

indoor


100

CAUSE 14: high level in a neighboring cell of a lower or an indoor layer for slow mobiles

in order to keep dual band MSs in the preferred band, cause 14 is not checked in the following cases, when EN_BI-BAND_MS(n) = DISABLED

The same scheme can be drawn between lower and indoor layers



CELL_BAND_TYPE = Preferred_band

CELL_LAYER_TYPE =

upper

CELL_LAYER_TYPE =

lower or indoor

EN_BI-BAND_MS = DISABLED

CELL_BAND_TYPE = CELL_BAND_TYPE(0)


CELL_BAND_TYPE Preferred_band

CELL_BAND_TYPE = Preferred_bandCELL_BAND_TYPE Preferred_band


101

CAUSE 14: high level in a neighboring cell of a lower or an indoor layer for

slow mobiles

If cell_layer_type (0) = upper

AV_RXLEV_NCELL(n) > L_RXLEV_CPT_HO(0,n)

and MS_SPEED = SLOW

and EN_MCHO_NCELL = ENABLED

Averaging window: A_PBGT_HO

Anti ping-pong: not checked if T_INHIBIT_CPT is running



mini

umbrella

micro indoor


102

CAUSE 14: high level in a neighboring cell of a lower or an indoor layer for

slow mobiles

If cell_layer_type (0) = lower

AV_RXLEV_NCELL(n) > L_RXLEV_CPT_HO(0,n)

and MS_SPEED FAST

and EN_MCHO_NCELL = ENABLED

Averaging window: A_PBGT_HO




mini micro

indoor


103

Speed discrimination objectives

maximize capacity (maximum traffic in microcells)

while optimizing quality (minimize the number of handovers)

Smart speed discrimination:

The higher the load in the umbrella cell, the higher the speed of MSs can be before

being directed to microcells

- to maximize capacity

- to maximize quality (avoid multiple handovers) when the load is low

Fast moving mobiles are directed to umbrella cells

a fast moving MS connected to a microcell or an indoor cell is directed to an

unloaded umbrella cell (see previous part)


Cause 14: speed discrimination (1/6)


104

Interlayer HO based on speed discrimination



Lower layer

Upper layer

Indoor layer

Cause12MS_speed = FAST

Cause12MS_speed = FAST

Cause14MS_speed = SLOW

Or INDEFINITE

Cause14MS_speed = SLOW


105

Speed discrimination process in umbrella cells

speed estimation based on the dwell time in the neighboring micro cells

if this dwell time exceeds MIN_DWELL_TIME, the MS is slow and is sent to the microcell

C_DWELL(n) is a counter measuring the number of SACCH periods of monitoring

neighboring cell n over the threshold L_RXLEV_CPT_HO(0,n)

C_DWELL(n) is compared to the threshold 2*MIN_DWELL_TIME in order to

determine MS speed

- MIN_DWELL_TIME is a variable linked to the load of the serving umbrella cell)

if for one neighboring cell n, C_DWELL(n) >= 2*MIN_DWELL_TIME then

MS_SPEED is set to SLOW




106

Initialization of C_DWELL(n) in serving umbrella cells:

for all neighboring cells n of a lower layer

if EN_SPEED_DISC = ENABLED

- C_DWELL(n) = 0

else if EN_SPEED_DISC = DISABLED

- C_DWELL(n) = (MIN_DWELL_TIME - L_MIN_DWELL_TIME)*2

Consequences

if EN_SPEED_DISC = DISABLED

MSs will handover to the lower layer after L_MIN_DWELL_TIME seconds

if EN_SPEED_DISC = ENABLED

MSs will have to receive sufficient level from a lower layer cell during

MIN_DWELL_TIME seconds before leaving the upper layer




107

Example with default values

Initial values

MIN_DWELL_TIME = H_MIN_DWELL_TIME = 20s

L_MIN_DWELL_TIME = 8s

C_DWELL(n) = (MIN_DWELL_TIME - L_MIN_DWELL_TIME)*2

C_DWELL(n) = ( 2 - 8 )*2

C_DWELL(n) = 12*2s

Algorithm

MS is deemed as slow if C_DWELL(n) > MIN_DWELL_TIME



0 2 4 6 8 10 12 14 16 18 20 22

: EN_SPEED_DISC = Disable

: EN_SPEED_DISC = Enable

INDEFINITE or FAST SLOW

Maximum time to reach

MIN_DWELL_TIME

=

L_MIN_DWELL_TIME

C_DWELL MIN_DWELL_TIMEC_DWELL


108

Traffic regulation through the variation of MIN_DWELL_TIME

Parameters: L_MIN_DWELL_TIME, DWELL_TIME_STEP,

H_MIN_DWELL_TIME, H_LOAD_OBJ, L_LOAD_OBJ



100 %

Load in the

umbrella Cell

H_LOAD_OBJ

L_LOAD_OBJ

L_MIN_DWELL_TIME

10 seconds

DWELL_TIME_STEP

5 seconds

H_MIN_DWELL_TIME

40 seconds

end: low traffic

start: low traffic

Regulation of

traffic peak

Default values

dependent on

the number of

TRXs

Default values: 8 seconds 2 seconds 20 seconds

MIN_DWELL_TIME

The initial value of MIN_DWELL_TIME is the H_MIN_DWELL_TIME parameter value.


109

CAUSE 24: general capture

new capture handover

Introduced in B6.2

Improved in B7 (anti ping-pong)

May be triggered

From all cells


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


Cause 24: general capture (1/3)


110


in order to keep dual band MS in the preferred band, cause 24 is not checked

in the following cases, when EN_BI-BAND_MS(n) = DISABLED



CELL_BAND_TYPE = Preferred_band


CELL_BAND_TYPE = CELL_BAND_TYPE(0)


CELL_BAND_TYPE Preferred_band


111


AV_RXLEV_NCELL(n) > L_RXLEV_CPT_HO(0,n) +


and Traffic_load(0) = CAPTURE_TRAFFIC_CONDITION

and Traffic_load(n) HIGH

and EN_GENERAL_CAPTURE_HO = ENABLED

Size of window for averaging level: A_PBGT_HO

CAPTURE_TRAFFIC_CONDITION can take 3 values: ANY_LOAD

(default), HIGH, NOT_LOW





112

Use of cause 21 or 14?

Considering the following network

Which cause has to be used for capture? 14 or 21?

Highlight one complexity linked to causes 14 and

21 interworking when using traffic discrimination


Exercises (1/3)

900

mini1800

Time allowed:

5 minutes

CAUSE 21: high level in the neighboring cell in the preferred band

AV_RXLEV_NCELL(n) > L_RXLEV_CPT_HO(0,n) +


and Traffic_load(0) = MULTI-BAND_TRAFFIC_CONDITION

and Traffic_load(n) HIGH

and EN_PREFERRED_BAND_HO = ENABLED

Size of window for average level: A_PBGT_HO

MULTI-BAND_TRAFFIC_CONDITION can take 3 values: ANY_LOAD (default), HIGH, NOT_LOW


113


Exercises (2/3)

Inputs Case 1 Case 2 Case 3 Case 4 Case 5 Case 6 Case 7 Case 8

Type Single Umbrella Umbrella Umbrella Multiband Multiband Micro Mini

Band 900 900 900 1800 900+1800 900+1800 900 900

Zone --- --- --- --- Outer Inner --- ---

Speed_disc Yes Yes No No No No Yes Yes

Rx_Lev(0) -84 dBm -60 dBm -90 dBm -90 dBm -90 dBm -90 dBm -60 dBm -90 dBm

Source

MS Speed Slow Slow Slow Slow Slow Slow Indefinite Fast

Type Micro Micro Mini Mini Mini Mini Indoor Indoor

Band 900 900 1800 900 1800 1800 900 1800

RxLev(n) -84 dBm -80 dBm -80 dBm -80 dBm -80 dBm -80 dBm -70 dBm -80 dBm

Target

EN_BI-BAND_MS Enable Enable Disable Disable Disable Disable Enable Disable

? Cause 14 ?

Time allowed:

5 minutes

Detection of cause 14

EN_MCHO_NCELL(0) = ENABLED

L_RXLEV_CPT_HO(0,n) = -85 dBm


114


Exercises (3/3)

Time allowed:

5 minutes

Speed discrimination

What is the role of parameter EN_SPEED_DISC?

If EN_SPEED_DISC is disabled, can fast MSs be

directed toward microcells?

What is the difference between EN_SPEED_DISC =

DISABLED and EN_SPEED_DISC = ENABLED when

L_LOAD_OBJ = 0% and H_LOAD_OBJ = 100%?


115




116

As soon as an intercell HO alarm has been detected

HO Detection sends to Candidate Cell Evaluation

the HO cause value

the preferred layer for the target cell indicated by the variable PREF_LAYER (it

depends on the cell network architecture and on the operator strategy)

the list of potential candidates (it depends on type of handover cause)


From HO Detection to Candidate Cell Evaluation

Candidate

Cell

Evaluation

Handover

Detection

Raw cell list

cell 1: cause C1

cell 2: cause C2

cell 3: cause C3

Max 32 cells

PREF_LAYER


117

Standard cell environment

CELL_LAYER_TYPE = SINGLE

Better condition HO cause

Emergency HO cause

* if the MS is in the DCS 1800 inner zone of a multi-band cell then it includes the

serving cell


Raw Cell List and PREF_LAYER (2/4)

upper + singlePREF_LAYE

R

subset of cells verifying the HO

causesRaw cell list


R

all neighboring cells*Raw cell list


118

Hierarchical cell environment

CELL_LAYER_TYPE = UPPER


Emergency HO cause

* if the MS is in the DCS 1800 inner zone of a multi-band cell then it includes the

serving cell



nonePREF_LAYE

R

subset of cells verifying the HO

causesRaw cell list


R

all neighboring cells*Raw cell list


119

CELL_LAYER_TYPE = LOWER or INDOOR


Emergency HO cause

* if the MS is in the DCS 1800 inner zone of a multi-band cell then it includes the serving cell



noneLower + indoorUpper + SinglePREF_LAYER

All neighboring cells* except

umbrella cells which do not

verify AV_Rxlev_Ncell(n) >

OUTDOOR_UMB_LEV(0,n)









Raw cell list

EN_RESCUE_UM = indefiniteEN_RESCUE_UM =

DISABLED

EN_RESCUE_UM =

ENABLED

noneUpperPREF_LAYER

Subset of cells verifying the

HO causes

Subset of cells verifying the HO

causes plus all neighboring

umbrella cells with

Traffic_Load(n) = LOW

Raw cell list

MS_SPEED FAST or

HO Cause 12

MS_SPEED = FAST and

There is a cell in the list

because of cause 12


120

Emergency handovers from lower or indoor layers

behavior depends on EN_RESCUE_UM

Normal parameter settings for minicells

EN_RESCUE_UM = DISABLED

thus PREF_LAYER = lower

Emergency handovers are preferably sent to neighboring minicells

Normal parameter settings for microcells

EN_RESCUE_UM = ENABLED

thus PREF_LAYER = upper + single

Emergency handovers are preferably sent to umbrella cells or neighboring

macrocells




121

MEASUREMENT PREPROCESSING

according

A_LEV_HO

A_QUAL_HO

A_PBGT_HO

A_RANGE_HO

Performed every SACCH

Measurement result

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 SACCH

Preprocess measurement

Raw 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

max EverySACCH

HO CANDIDATE CELLS EVALUATION

Priority (0,n) = 0

cell 2: cause C2

cell 3: cause C3

cell 4: cause C4

Priority (0,n) = 1

cell 1: cause C1

Priority (0,n) = 2

Priority (0,n) = 3

cell 5: cause C5

cell 6: cause C6

cell 7: cause C7

cell 8: cause C8

PRE-RANKING

PBGT_FILTERING

HO_MARGIN_XX(0,n)

Priority (0,n) = 0

cell 2: cause C2

cell 3: cause C3

cell 4: cause C4

Priority (0,n) = 1

-----------------------

Priority (0,n) = 2

Priority (0,n) = 3

----------------------

cell 6: cause C6

-----------------------

cell 8: cause C8

CELLS EVALUATION PROCESS

Order or Grade

Grade

Priority (0,n) = 0

cell 4

cell 2

Priority (0,n) = 1

Priority (0,n) = 2

Priority (0,n) = 3

cell 8

Order

Priority (0,n) = 0

cell 4

cell 3

cell 2

Priority (0,n) = 1

Priority (0,n) = 2

Priority (0,n) = 3

cell 8


Evaluation process

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

In case of intra-cell 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 the 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=ENABLED) 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 multi-band 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=ENABLED).


122


Pre-ranking in standard networks

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 a 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 and PBGT

nevertheless it can be skipped over by filtering processes

low interest for standard networks

Serving cell

Candidate cell 1: RxLev: - 70 dBm, pbgt: + 10 dB

Candidate cell 2: Rxlev: - 90 dBm, PBGT: + 5dB

P0

P1

PRIORITY(0,n) can take 6 different values since B7, to take into account new indoor layers.


123

In hierarchical or multi-band networks, pre-ranking is used

For emergency handovers + Forced Directed Retry

Cell_layer_type: single, upper, lower, indoor

PRIORITY(0,n): 0 to 5

Cell_band_type: GSM or DCS

For better condition handovers

Cell_layer_type: single, upper, lower, indoor

PRIORITY(0,n): 0 to 5

PRIORITY(0,n) are taken into account only if EN_PRIORITY_ORDERING is

set to enabled on the serving cell


Pre-ranking in complex networks (1/3)


124

Pre-ranking in case of emergency HO, plus cause 20 and 28 :



Cell_layer_type = Pref_layer

Cell_layer_type Pref_layer

List of candidate cells n

Cell_band_type = serving cell

Cell_band_type serving cell

Priority(0,n) = 0

Priority(0,n) = 1

Priority(0,n) = 5

Priority(0,n) = 0

Priority(0,n) = 1

Priority(0,n) = 5


125

Pre-ranking in case of better condition HO:



Cell_layer_type = Pref_layer

Cell_layer_type Pref_layer

List of candidate cells n

Priority(0,n) = 0

Priority(0,n) = 1

Priority(0,n) = 5

Priority(0,n) = 0

Priority(0,n) = 1

Priority(0,n) = 5


126


PBGT Filtering

PBGT filtering: process introduced since B5

optional, activated through the flag EN_PBGT_FILTERING

filter out cells from the target list

inhibited for better conditions handovers

based on power budget

Mandatory for multi-band networks

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

HO_MARGIN_XX (0,n) = HO_MARGIN_QUAL (0,n) for causes 2, 4, 7

HO_MARGIN_XX (0,n) = HO_MARGIN_LEV (0,n) for causes 3, 5, 17, 18, 28

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 average 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 pe

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