Alcatel Ho 2g Preparation

Handover PreparationED 01 RELEASED

MCD 276_01RL.DOC13/11/1998 3BK 11202 0276 DSZZA 1/5

All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.

SiteVELIZY MOBILE COMMUNICATION DIVISION

Originator(s)

P-J PIETRIHANDOVER PREPARATION

RELEASE B6.2

Domain : Alcatel 900/BSSDivision : PRODUCT DEFINITIONRubric : SYS-TLAType : SYSTEM FUNCTIONAL BLOCKSDistribution Codes Internal : External :

PREDISTRIBUTION:

MCD - Velizy MCD - Colombes MCD - BerlinJY. AMAUDRUT M. DELPRAT U. Klingner (for Tel par)O. BESSET M. DOBROSIELSKIF. COLIN JP. JARDELL. CRUCHANT JL. LEKMOULI SSD - VelizyJ. ACHARD A. PECHP. FOUILLAND B. LANDAIS MCD - KontichM. WU B. BEN SALEM G. VAN DIJCK (ffd)S. BOURDEAUT N. De BODEM. ROBERTSR. FORNIP.DUPUY MCD Stuttgart SSD - StuttgartE. DESORBAY G. HOEN

J.F. MAILLARD (ffd)

PREDISTRIBUTION: DOC. CENTRES

MCD VELIZY MCD STUTTGART MCD ANTWERPB. Marliac I. Lentzsch L. Van Eyck

ABSTRACT

This document specifies the algorithms to be implemented in this release of the Alcatel BSS for :

- Handover preparation,- Directed retry preparation.

Approvals

Name

App.

D.BerthoumieuxAM

M. BIALOBRODAS.S.A.M. - BTS_SW

M. ROELANDTSS.S.A.M. - BSC

Name

App.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.

REVIEW

Ed 01 P01 10/11/98 TD/SYT/PJP/1159.98

HISTORYRelease 2 : S/P2/3.4.1.4.3

Version Date Author Reasons for update

2.0.0.0 18/05/92 B. Maier First working version for phase 2 based on the document:- TLA/148 V 1.2.0.0 written by P. GUILLIER and D.VERHULST- CRQ/757- TLA/SN/3 v.2.1.0.0 and TLA/SN/30 v.2.2.0.0.

2.0.0.1 19/06/92 B. Maier Second working version.

2.0.0.2 10/03/93 B. Maier Third working version.The document is reviewed according to the new templatefor phase 2 documents.

2.0.1.0 14/05/93 L. Cruchant First TLA approved version for phase 2.This version takes into account remarks made duringTLA review (see RSG/160).DCS-1800 features are introduced in the document.

2.1.0.0 27/08/93 L. Cruchant First RSG approved version for phase 2.This version takes into account remarks made duringRSG/TLA review (see TLA/153).

Release 3 : 3BK 11202 0014 DSZZA

3.0.0.0 15/12/93 L. Cruchant First working version for release 3 based on thedocuments :- Power Control and Handover Algorithms v.2.1.0.0,- TLA/152 improvements, v 2.0.0.5 : PCHO 002, PCHO 005, EXH 003.- FD/3/10.6 : Support of microcellular environment v 3.0.0.1,- FD/3/10.7.1 : Concentric cells v 3.0.0.1,- FD/3/10.8 : Directed Retry v 3.0.0.0,

3.0.0.1 04/03/94 L. Cruchant Second working version for release 3. This documenthas been updated after the meeting TLAr3#1 (seeTLA/171).Additional information has been added based ondocuments SYS/006 : definition of parameters for cellenvironments (H. Brinkmann, G. Kreft).SYS/014 : Handover in a microcellular environment (C.Cherpantier).

3.0.1.0 11/04/94 L. Cruchant First Level 1 approved version for release 3, updatedafter the meeting TLAr3#4 (see SYS/030).



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.

3.1.0.0 11/05/94 L. Cruchant Level 2 approved version, updated after the meetingTLAr3#7 (see SYS/051).


4.0.0.0 04/11/94 L Julia First working version for release 4 based on thedocuments- Power Control and Handover Algorithms v 3.1.0.0- MFD 11.5 : Power control and handover algorithmimprovements- ITCC/TELACT/TEL/PP/006 : remarks made by ITC onspecifications for rel 3

4.0.0.1 26/01/94 L Julia Updated after the TLAr4#4 review ,based on thedocuments- SYS/111Minutes of the TLA review TLAr4#4- CRQ/729 Expand of POWER_INC_STEP range forDCS 1800

4.0.0.2 23/02/95 L Julia Updated after the TLAr4#8 review, based on the writtencomments form S. De FOORT and A. KADELKA andthe minutes SYS/142 of the TLAr4#8 meeting

4.0.1.0 03/04/95 L Julia Level 1 approved version, Updated after the TLAr4#9review, written comments by N. De BODE, minutesSYS/149 of the TLA review.

4.1.0.0 05/05/95 L Julia Level 2 approved version, Updated after writtencomments by N. De BODE and C. CHERPANTIER.approved Release 3 CRQ taken into account : CRQ 924,CRQ 1153, CRQ 1173, CRQ 1258, CRQ 1279, CRQ1281, CRQ 1282, CRQ 1283, CRQ 1294, CRQ 1312


Ed. 01 Proposal 01 08/03/96 F Colin First working version for release 5 based on the documents:- Power Control and Handover Algorithms v 4.1.0.0 (This document has been split in two : the present document resumes the part ’Handover algorithms’)- TFD 11.22 a : Handover algorithms improvements

Multiband Handover- Approved Release 4 CRQs : CRQ 1428, CRQ 1705, CRQ1806, CRQ 2027, CRQ 2093, CRQ 2109, CRQ 2144, CRQ2234Moreover, the original document has been partly modified :- Mode A has been removed- Section 3 has been reorganised, section 2.2 removed- Appendix B and F have been removed, Appendic C is newMinor changes are listed in Appendix D

Ed. 01 Proposal P1 30/04/96 F Colin Document updated after the internel review TLAr5#9according to the minutes in ref. TD/SAS/LCR/747.96



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.

Ed. 01 Proposal R1 14/06/96 F Colin Document updated after the prereview TLAr5#12 accordingto the minutes in ref. TD/SAS/LCR/1062.96, based on thecomments of N. de Bode and G. Van DijckIntroduction of DCS1900 supportIntroduction of approved Release 4 CRQs : CRQ 1971,CRQ 2408 and CRQ 2472.

Ed. 01 Released 23/07/96 F Colin Document updated after the external review TLAr5#15according to the minutes in ref. TD/SAS/LCR/1377.96,based on the comments of N. de Bode.Creation of Section 5 ’Release changes’Introduction of approved Release 4 CRQs : CRQ 2504,CRQ 2505

Release 6.1 : 3BK 11202 0170 DSZZA

Ed. 01 Proposal 01 29/08/97 PJPIETRI

First working version for release 6 based on the documents:- Handover preparation release 5 Ed. 01- TFD 11.31: general handover algorithms improvements- TFD 10.8b: external directed retry- TFD 11.22.e controlled handover in multilayer/multivendorenvironment- TFD 11.30: traffic management in handover algorithms- TFD 3.19: HSCSD- TFD 11.32: improvements in radio channel selection- Approved Release 5 CRQs 18579, 3028, 2736, 10645,19733The section 2 is reorganised. Some descriptions have beenput in a new step 1 document (refer to [21]).The section Active channel preprocessing is in the newdocument Radio measurements data processing [20].A new handover alarm management is specified in section3.2.4.


Document updated after the review TLAr6#15 according tothe minutes in ref. TD/SAS/LCR/1218.97Modification of the directed retry management.

Ed. 01 Released 15/10/97 PJPIETRI

Approved version, updated following TLA review TLAr6#17,as detailed in TD/SAS/EDE/1317.97


Second working version for release 6 based on the followingmodifications :- Suppresion of the handover cause 24- HSCSD calls are allowed in the inner zone of a concentriccell.-Inhibition of the filtering process for the handovers cause20.


Approved version, updated following TLA review TLAr6#20,as detailed in TD/SAS/EDE/0104.98


Updated after inclusion of approved Crqs: Crq 29140, Crq29147 and Crq 30481


Updated after inclusion of approved Crqs: Crq 30932, Crq32529, Crq 33156 and Crq 40894.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.



First working version for release 6 based on the documents:- Handover preparation release 6.1 Ed. 04- TFD GPRS


Approved version, updated as detailed inTD/SYT/PJP/1159.98

INTERNAL REFERENCED DOCUMENTS

[i1] 3BK 10204 0347 DRZZA - HSCSD[i2] 3BK 10204 0327 DTZZA - General handover improvements[i3] 3BK 10204 0326 DTZZA - Traffic management in handover algorithms[i4] 3BK 10204 0363 DTZZA - Improvements in radio channel selection[i5] 3BK 10204 0364 DTZZA - Controlled handover in multilayer/multivendor environment[I6] 3BK 10204 0165 DRZZA - External directed retry

FOR INTERNAL USE ONLY

By derogation to the QS recommendation (see document 8BL 14106 0000 BGZZA - TDdocumentation layout) more than 3 levels used in the table of contents with agreement of the PQE.

END OF DOCUMENT


MCD 276_01RL.DOC13/11/98 14:48 3BK 11202 0276 DSZZA 1/94

All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.

SYSTEM FUNCTIONAL BLOCKS

TABLE OF CONTENTS

HISTORY.......................................................................................................................................... 2

REFERENCED DOCUMENTS.......................................................................................................... 2

RELATED DOCUMENTS ................................................................................................................. 2

PREFACE......................................................................................................................................... 2

1. SCOPE .......................................................................................................................................... 5

2. FUNCTIONAL DESCRIPTION....................................................................................................... 52.1 Overview ............................................................................................................................. 52.2 Cell configuration............................................................................................................... 5

2.2.1 Cell Environments ..................................................................................................... 52.2.1.1 Conventional cell environment ........................................................................ 62.2.1.2 Hierarchical cell environment .......................................................................... 82.2.1.3 Multiband cell environment ............................................................................. 9

2.2.2 Cell profiles ............................................................................................................... 92.3 Handover preparation ...................................................................................................... 12

2.3.1 Functional entities of handover preparation ............................................................. 122.3.2 Specific cases of application.................................................................................... 142.3.3 Handover detection.................................................................................................. 14

2.3.3.1 Emergency intercell handovers ..................................................................... 152.3.3.1.1 Quality and Level causes ................................................................... 152.3.3.1.2 Too long MS-BS distance cause......................................................... 152.3.3.1.3 Too short MS-BS distance cause ....................................................... 152.3.3.1.4 “Consecutive bad SACCH frames” and “level dropping under high

threshold”.................................................................................................. 152.3.3.2 Better cell handovers .................................................................................... 15

2.3.3.2.1 Power budget cause........................................................................... 162.3.3.2.2 Better cell cause specific to hierarchical network................................ 172.3.3.2.3 Preferred band cause......................................................................... 172.3.3.2.4 Traffic handover ................................................................................. 17

2.3.3.3 Emergency intracell handovers ..................................................................... 182.3.3.4 Better zone handovers.................................................................................. 18

2.3.4 Handover candidate cell evaluation ......................................................................... 192.3.4.1 Cell ordering according to target layer and target band ................................. 192.3.4.2 Filtering process............................................................................................ 192.3.4.3 Candidate cell ranking................................................................................... 19

2.3.5 Inhibition of handover .............................................................................................. 202.3.6 Functional diagram of Handover preparation ........................................................... 22

2.4 Directed retry preparation................................................................................................ 262.4.1 System aspects ....................................................................................................... 262.4.2 Functional description.............................................................................................. 272.4.3 Directed retry on handover alarms........................................................................... 282.4.4 Forced directed retry................................................................................................ 282.4.5 Inhibition of directed retry ........................................................................................ 28

3. DYNAMIC BEHAVIOUR .............................................................................................................. 313.1 Functions linked to handover preparation ..................................................................... 31

3.1.1 Concentric cell and multiband cell............................................................................ 313.1.1.1 Allocation in the inner zone in case of Normal Assignment............................ 313.1.1.2 Allocation in the inner zone in case of incoming handover ............................ 313.1.1.3 Handover in a concentric or multiband cell .................................................... 32

3.1.2 MS speed discrimination.......................................................................................... 33



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.

3.1.2.1 Basic principle............................................................................................... 333.1.2.2 Required parameters and variables............................................................... 333.1.2.3 Parameter initialisation and modification ....................................................... 34

3.1.3 Load management in hierarchical environment........................................................ 363.2 Handover preparation ...................................................................................................... 38

3.2.1 General ................................................................................................................... 383.2.1.1 HO preparation configuration ........................................................................ 383.2.1.2 HO preparation enabling and disabling.......................................................... 383.2.1.3 HO preparation function ................................................................................ 38

3.2.2 Handover detection.................................................................................................. 413.2.2.1 Handover causes.......................................................................................... 41

3.2.2.1.1 Intercell handover causes................................................................... 423.2.2.1.1.1 Emergency intercell handover causes ............................................. 423.2.2.1.1.2 Forced intercell handover cause on quality...................................... 443.2.2.1.1.3 Better cell handover causes ............................................................ 453.2.2.1.2 Intracell handover causes................................................................... 483.2.2.1.2.1 Emergency intracell handover causes ............................................. 483.2.2.1.2.2 Better zone handover cause............................................................ 49

3.2.2.2 Handover causes priority............................................................................... 533.2.2.3 Indication of raw cell list and preferred layer ................................................. 53

3.2.3 HO Candidate Cell Evaluation ................................................................................. 563.2.3.1 Filtering process............................................................................................ 593.2.3.2 ORDER cell evaluation process .................................................................... 593.2.3.3 GRADE cell evaluation process .................................................................... 603.2.3.4 Calculation of LOADfactor, FREEfactor ........................................................ 62

3.2.4 Handover alarm management ................................................................................. 633.3 Directed retry preparation................................................................................................ 64

3.3.1 General ................................................................................................................... 643.3.1.1 Directed retry preparation enabling and disabling.......................................... 643.3.1.2 Directed retry preparation function ................................................................ 64

3.3.2 Alarm Detection ....................................................................................................... 643.3.3 Candidate cell evaluation......................................................................................... 65

4. INTERFACES DESCRIPTION ..................................................................................................... 694.1 GSM interfaces/Physical interfaces................................................................................. 694.2 Internal interfaces............................................................................................................. 694.3 Timers list ......................................................................................................................... 694.4 Parameters and variables list .......................................................................................... 69

4.4.1 Handover................................................................................................................. 704.4.2 Directed retry........................................................................................................... 794.4.3 Relationships between parameters .......................................................................... 81

5. RELEASE CHANGES.................................................................................................................. 85

6. FEATURES.................................................................................................................................. 86

7. GLOSSARY................................................................................................................................. 877.1 Abbreviations ................................................................................................................... 877.2 Definitions......................................................................................................................... 88

APPENDIXES

A: Power budget equation

B: Recapitulation of the cell types allowed for the serving and the candidate cell for eachhandover cause

C: Compliancy with the GSM requirements

Han

do

ver Prep

aration

ED

01 R

EL

EA

SE

D

MC

D276_01R

L.DO

C13/11/98 14:48

3BK

11202 0276 DS

ZZ

A3/94

All rights reserved. Passing on and copying of this document, use and communication of its contents

not permitted without written authorization from Alcatel.

0110/11/98

MC

D/T

DM

CD

/TD

/SY

TE

DD

AT

EC

HA

NG

E N

OT

EA

PP

RA

ISA

L A

UT

HO

RIT

YO

RIG

INA

TO

R



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.

HISTORY


Ed. 01 10/11/98 First edition

REFERENCED DOCUMENTS

GSM references

[1] 04.08 MS-BS Layer 3 Specifications.[2] 05.08 Radio Subsystem Link Control.[3] 08.58 BSC-BTS Layer 3 specification.

Version numbers of the GSM Technical Specifications are given in ref [15].

Doctree references

[4] 3BK 11202 0194 DSZZA - Application document 05.xx.[5] 3BK 11204 0176 DSZZA - OMC BSS MIB specification.[6] 3BK 11202 0154 DSZZA - Radio & link establishment.[7] 3BK 11202 0155 DSZZA - Normal Assignment[8] 3BK 11202 0166 DSZZA - Radio measurements.[9] 3BK 11202 0217 DSZZA - Internal channel change.

[10] 3BK 11202 0216 DSZZA - External channel change.[11] 3BK 11202 0157 DSZZA - Call release.[12] 3BK 11202 0175 DSZZA - BSS initialisation of the telecom part.[13] 3BK 11202 0209 DSZZA - BSS Telecom parameters.[14] 3BK 11202 0215 DSZZA - Handover management[15] 3BK 11203 0012 DSZZA - Alcatel BSS Application document to GSM - General Overview.[16] 3BK 11202 0214 DSZZA - Resource allocation and management.[17] 3BK 11202 0185 DSZZA - Extended Cell[18] 3BK 11202 0169 DSZZA - Power Control & Radio link supervision[19] 3BK 11202 0199 DSZZA - System Information management[20] 3BK 11202 0168 DSZZA - Radio Measurements Data Processing[21] 3BK 11203 0042 DSZZA - Radio link and radio resource management

RELATED DOCUMENTS

[22] CCITT Z100. Structured Definition Language.[23] GEODE user manual. VERILOG.[24] ART/DST/PFK/20 - ALCATEL_BSS phase 1 description of radio link control algorithms and

guidelines for setting parameters values. ART/DST/PFK/20

Note : most of the SDL diagrams have been produced with the software tool GEODE which is atrademark of VERILOG ([0]). The SDL standard is defined in [22].

PREFACE

Not Applicable



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.

1. SCOPE

This document specifies the algorithms to be implemented in this release of the ALCATEL BSS for :- handover preparation,- directed retry preparation,- GPRS redirection preparation.

Handover preparation consists of two functions which are considered separately in this document :- detection of the need to handover a radio connection,- candidate cell list evaluation.

Directed retry and GPRS redirectionpreparation are specified along with handover preparation.

2. FUNCTIONAL DESCRIPTION

2.1 Overview

The main objective of the handover preparation, in connection with power control (see [18]), is toallow a maximum number of MS to operate in the network while maintaining a minimum interferencelevel. The algorithms shall ensure that any mobile is connected with the cell in which the outputpowers from the MS and the BS are as low as possible (to reduce MS power consumption andinterference in the network) while keeping a satisfactory link quality.

When on a sufficient duration the propagation conditions keep worsening, then action must be taken.The first action is to increase the output power levels at the MS or the BS (for further details, see[18]). When the maximum allowed value has been reached, a handover may become necessary.

To reflect this philosophy in macrocells (not in microcellular environment), the algorithm allows forhandover on quality and strength reasons only when the last step of power control has been reached.

Great care must be taken in choosing the relative values of the thresholds for power control andhandover as well as the averaging window sizes (smaller window size and higher threshold for powercontrol than for handover). It must be remembered that, although it is desired that the MS transmitswith the lowest possible power, it is more important not to lose a call. Thus early triggering for thepower control is possible, by choosing small values for the averaging window sizes and highercomparison thresholds.

For further description about handover preparation refer to [21].

The GPRS redirection consists, when a MS asks for a GPRS service and the selected cell does notsupport GPRS, to sent a cell change order to the MS indicating a cell supporting GPRS. For that afterreception of a packet request, a SDCCH is assigned to the MS in a way to collect measurements onthe neighbour cells and so to be able to select a target cell supporting GPRS.

2.2 Cell configuration

2.2.1 Cell Environments

Three types of cell environments are supported : conventional cell environment, hierarchical cellenvironment and multiband cell environment.In the conventional cell environment, the cell planning is made so as to obtain a continuousgeographical coverage .The hierarchical cell environment corresponds to a layout of two cell layers with different cell sizes.The large cells layer is called "upper layer" and the small cells layer "lower layer". This environment ismeant to be used in advanced networks.

The interest of the lower cell layer is twofold:



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.

- densify the traffic by providing a smaller frequency reuse distance in the lower layer- compensate traffic density unbalance by using small cells located at traffic "hot spots"

The interest of the upper cell layer is to :- provide continuous geographical coverage- handle fast moving mobiles in order to avoid high handover rate- provide overflow and rescue channels for the lower cell layer

Reflecting this representation, the upper layer cells are often called "umbrella cells".

The multiband cell environment consists in two layers of cells using different frequency band. Theinterest of the multiband network is to increase the capacity or the coverage of the network.

2.2.1.1 Conventional cell environment

Three different layouts are provided for conventional cell environment , in order to adapt to the trafficdensity :

- single cellThe figure 2.2-1 represents the possible geographical layouts with single cells.

- concentric cell : a macrocell with two frequency groups covering two concentric zones. Thisallows to use a smaller reuse distance for the inner zone frequencies and hence to densify anexisting network by introducing a small number of frequencies at the needed places.The figure 2.2-2 shows the smaller reuse factor (here 3) for the inner zone frequencies in atraditional 9 cell cluster.

- multiband cell : a concentric cell in which:the outer zone, that includes the BCCH, the SDCCH and several TCH channels, will usefrequencies from the classical band.The inner zone, that includes only TCH, will all use frequencies from the preferred band.

- extended cell where two cells with collocated antennas provide coverage up to 70 km. Theapplication fields are both the low density areas and the off-shore coverage for coastal radiocommunications.The figure 2.2-3 illustrates the layout of two associated cells making an extended cell. Forreference information on that feature, see[17].

sectorized cell for site reductionomnidirectional macrocell

figure 2.2-1 : normal cell environment with one cell layer

Han

do

ver Prep

aration

ED

01 R

EL

EA

SE

D

MC

D276_01R

L.DO

C13/11/98 14:48

3BK

11202 0276 DS

ZZ

A7/94

All rights reserved. Passing on and copying of this document, use and communication of its contents

not permitted without written authorization from Alcatel.

f1f1

f3

f2

f2

f3

f3f1

f2

Inner zone

Outer zone

One concentric cell

figure 2.2-2 : concentric cell frequency planning

figure 2.2-3a : extended cell with directional antennas

inn

er cell

ou

ter cell

50 km radius

outer limit

inner limit

outer limit

figure 2.2-3b : extended cell with om

nidirectional antennas

outer cell

inner cell

Highw

ay

70km

35 km



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.

2.2.1.2 Hierarchical cell environment

In much denser traffic areas, depending on the required traffic capacity, the operator may wish tohave a hierarchical network, where continuous coverage is provided by a standard macrocell, andtraffic hot spots are covered with dedicated cells of limited range.The solution for medium density areas is to have small macrocells (called mini cells) , to handlepedestrian traffic, overlapped with one big umbrella macrocell , to handle fast moving mobiles.The solution for higher traffic densities will be to install microcells in all the streets where verydense traffic occurs. Umbrella macrocells will be providing the continuous coverage and the trafficchannels for saturated microcells and "emergency" handovers.

- mini cells with umbrella macrocells

This configuration will be of main interest for dense urban areas where some hot-spots arecovered by very small macrocells (less than 500 m radius) and continuous coverage is providedby a big macrocell (5 to 10 km radius).The figure 2.2-4 presents a possible application of the two-layer hierarchical network withmacrocells for both layers, in a middle size town.

Super umbrella cellR~10 km

mini cells0.5<R<1 km

pedestrian areafigure 2.2-4 : cell layout with mini cells below one umbrella cell

- microcells with umbrella cells

One layout is provided for microcellular applications, that should apply to very highly dense trafficareas or when the available spectrum is very reduced. The figure 2.2-5 presents the cell layout formicrocells covered by an umbrella cell to provide continuous coverage and decreased blockingrate.The densification strategy for microcellular enables to use the already existing macrocell layer forthe umbrella cells.Therefore, it may be possible for the operator to use already installed single (or concentric ormultiband) cells as umbrella cells for a microcellular network.

existing cells1<R<2 km

microcellsR < 300 m



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.

figure 2.2-5 : typical microcellular layout

2.2.1.3 Multiband cell environment

An operator with licenses in the different frequency bands (GSM and DCS) can mix in its networkcells which use GSM frequency band with cells using DCS frequency band. This case is referred to asmultiband cell environment.

Multiband cell environment is supposed to be made out of a main part with cells of same frequencyband. This band is the oldest one acquired by the operator and it is the most used in its network : it iscalled the classical band. As this band was first used alone, there is no doubt that cells of classicalband ensure the coverage of the network.

With the other frequency band, the operator will add new cells to its network. As the cells of theclassical band guarantee a sufficient coverage, the assumption is made that these new cells areadded in order to increase the traffic capacity of the network rather than to improve the coverage.

This assumption determines the handover strategy in multiband cell environment. This strategymainly consists in preferably redirecting multiband mobiles (mobiles with capability in both frequencybands) in the new cells which use the frequency band different from the classical one. That is whythis band is called the preferred band.

Multiband cell environment can be applied to conventional cell environment as well as hierarchicalcell environment. In this last case, the multilayer structure will interact with the multiband concept.

2.2.2 Cell profiles

The optimisation of the use of the frequency resources is a main concern for network operators.The Alcatel BSS provides a span of cell environments that allows to cover the whole range of trafficdensity requirements : from very dense urban centres with microcells up to very low traffic areas(desert or off shore) with extended cell sites.These different types of cell environment must be controlled and administered in a flexible way by theoperator.For this purpose, the Alcatel BSS provides a set of cell profiles, which enable the operator to make astarting point configuration by just applying the default values of the profile. Each profile provides allthe configuration data associated to one given cell as default settable values. This includes handoverparameters, but also power control settings, timers .

Eight main profiles are defined : single cell, micro cell, mini cell, umbrella cell, extended inner cell,extended outer cell, concentric cell, concentric umbrella cell. These profiles are duplicated by theinternal parameter cell_band_type which can have two different values for each profile. In order togive the operator the possibility to have its personal usage of the ALCATEL parameters, the profilesare user-editable. This means that all default values associated to one given profile can be modifiedto reflect the standard usage of the operator.

These cell profiles correspond to one unique combination of the five parameters :- Cell dimension type : this parameter identifies the cell size in a finite set of cell dimensions(macro or

micro).- Cell layer type : this parameter defines the layer type of a cell in connection with other cells and with

itself. In single layer cell environment, all cells have the same layer type (single). In a hierarchicalcell environment, two cell layer types distinguish the upper layer cells and the lower layer cells.

- Cell_partition type : this parameter defines the type of frequency partitioning that is used in the cell.- Cell range : this parameter identifies the cell as a normal cell or a part of an extended cell- Cell_band_type : this parameter defines the type of frequency band used in the cell

The first three parameters are settable on a per cell basis and changeable on-line by O&M.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.

The cell_range parameter is set at BTS initialisation time and only changeable off-line.Cell_band_type is an internal parameter derived from the BCCH frequency of the serving cell(BCCH_FREQ) or from the BCCH frequency index of the neighbour cells n (FREQ(n)), reported bythe mobile.

Cell dimension typeTwo values are possible : ### Macrocell.

### Microcell.

Future envisaged value : picocell for Personal Communication Services.

Cell layer typeThree values are possible : ### Single : this applies to all cells in normal environment (1 cell layer)

### Upper : this indicates the upper layer cells in a hierarchical cellenvironment with two layers. These cells are also called "umbrella cells" andthey will have at least one associated lower layer cell, otherwise they aresingle cells.

### Lower : this indicates the lower layer cells in a hierarchical cellenvironment with two layers. Each lower layer cell will have one associatedumbrella cell, otherwise it is deemed "single".

A single cell has no cells included within its coverage area.

Cell partition typeTwo values are possible : ### Normal partition.

### Concentric partition.

The concentric partition corresponds to the concentric or multiband cell case. In this case, thefrequency carriers are assigned to one or the other of the two concentric zones : inner and outer.

Future envisaged values : Cell with dynamic frequency use partitioning based on Space DivisionMultiple Access (SDMA).

Cell rangeThree values are possible : ### Normal

### Extended inner### Extended outer

Cell band typeTwo values are possible : ### GSM

### DCS

Cell_band_type is an internal parameter whose value depends on the BCCH frequency of the servingcell (BCCH_FREQ) or on the BCCH frequency index given by the mobile for every reportedneighbour cells (FREQ(n), refer to [20]).

For the serving cell :

Cell_band_type = GSM if BCCH_FREQ corresponds to GSM900 frequency band (extended bandincluded).Cell_band_type = DCS if BCCH_FREQ corresponds to DCS1800 or DCS1900 frequency band.

For neighbour cell n :



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.

Cell_band_type(n) = GSM if FREQ(n) corresponds to GSM900 frequency band (extended bandincluded).Cell_band_type(n) = DCS if FREQ(n) corresponds to DCS1800 or DCS1900 frequency band.

Note : the correspondence between FREQ(n) and the frequency band of the neighbour cell n isperformed through the neighbour cell list (for further details see [19]).

Cell configurationIn the following "Cell configuration" will refer to the combination of the five parameters :- Cell dimension type,- Cell layer type,- Cell partition type,- Cell range,- Cell band type.

In this release of the ALCATEL BSS, all the possible cell configurations are given in table 2.2-1.All the other cell configurations are forbidden as they are not relevant for operation.The O&M functions shall ensure that the cell configurations managed by the handover preparationare authorised. The selection of one given cell profile for applying default values will force the valueof the cell configuration.

Cell Profile Cell dimensiontype

Cell layer type Cell partitiontype

Cell range Cell bandtype

GSM single cell Macro Single Normal Normal GSM

DCS single cell Macro Single Normal Normal DCS

GSM micro cell Micro Lower Normal Normal GSM

DCS micro cell Micro Lower Normal Normal DCS

GSM mini cell Macro Lower Normal Normal GSM

DCS mini cell Macro Lower Normal Normal DCS

GSM umbrella cell Macro Upper Normal Normal GSM

DCS umbrella cell Macro Upper Normal Normal DCS

GSM extended inner cell Macro Single Normal Extended-inner

GSM

DCS extended inner cell Macro Single Normal Extended-inner

DCS

GSM extended outer cell Macro Single Normal Extended-outer

GSM

DCS extended outer cell Macro Single Normal Extended-outer

DCS

GSM concentric cell Macro Single Concentric Normal GSM

DCS concentric cell Macro Single Concentric Normal DCS

GSM concentricumbrella

Macro Upper Concentric Normal GSM

DCS concentric umbrella Macro Upper Concentric Normal DCSTable 2.2-1 : Allowed cell configurations

A multiband cell is declared by setting the FREQUENCY_RANGE to “GSM-DCS”. TheCELL_PARTITION_TYPE of the cell is then forced to CONCENTRIC.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.

Note : - The duplication of the main profiles according to the values of the cell band type isperformed for every main profile. It gives a few cell profiles not really relevant (such as DCSextended outer cell profile) but it prevents from dealing with exceptions.

The figure 2.2-1 depicts the configurations of table 2.2-1 for cell_range = normal and with differentvalues of cell band type.

Cell_dimension type : macroCell_layer_type : upperCell_partition_type : concentricCell_band_type : GSM

Cell_dimension type : macroCell_layer_type : upperCell_partition_type : normalCell_band_type : GSM

Cell_dimension type : macroCell_layer_type : singleCell_partition_type : concentricCell_band_type : DCS

Cell_dimension type : macroCell_layer_type : lowerCell_partition_type : normalCell_band_type : GSM

Cell_dimension_type : macroCell_layer_type : singleCell_partition_type : normalCell_band_type : DCS

Cell_dimension type : microCell_layer_type : lowerCell_partition_type : normalCell_band_type : DCS

Figure 2.2-1 : Allowed cell configurations for cell_range = normal and different values of cell band type

2.3 Handover preparation

This function can also be named "handover algorithms" as the algorithms described in section 3 arethe "heart" of this function. In the following the word "handover preparation" will be preferred to"handover algorithms".

The ALCATEL handover preparation is derived from the basic algorithm found in Annex A of theGSM Technical Specification 05.08 ([2]). The main differences between both algorithms aredescribed in [4].

2.3.1 Functional entities of handover preparation

The handover preparation is in charge of detecting a need for handover and proposing a list of targetcells. Therefore it can be divided into two processes : handover detection and handover candidatecell evaluation.

The handover detection process analyses the radio measurements reported by the BTS and triggersthe candidate cell evaluation process each time a handover cause (emergency or better cell type) isfulfilled.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.

The handover candidate cell evaluation works out a list of possible candidate cells for the handover.

This list is sorted according to the evaluation of each cell as well as the layer they belong to (in ahierarchical network) and the frequency band they use (in a multiband network).Once the handover preparation is completed, the handover decision and execution (handovermanagement entity refer to [14]) is performed under the MSC or BSC control. The directed retrypreparation (see definition in section 2.4) is performed by the handover preparation function.

Once the directed retry preparation is completed, the directed retry is performed either under the BSCcontrol (internal directed retry) or under the MSC control (external directed retry). These proceduresuse signalling protocols described respectively in [9] and [10].

An example of implementation of these functions except for directed retry is given in the GSMTechnical Specification 05.08 [2].

The handover preparation requires indirectly (see below) input parameters provided by the function incharge of the radio link measurements. This function is described in [8].

Most of the input data required by the handover functions are provided by a function called : Activechannel pre-processing. This function is described in [20]. It processes raw data given by the radiolink measurements (quality, level and distance) through the A-bis interface in compression mode ornon compression mode. The compression mode uses two functions: Radio measurements datacompression in the BTS and Radio measurements data decompression in the BSC. They aredescribed in [20].

The functions handover detection and handover candidate cell evaluation are specified in thisdocument.

The figure 2.3-1 depicts in a general way :- the interconnections between these functions,- the implementation of these functions in the ALCATEL BSS. The functions which are specified inthis document are represented in bold type.

BTS BSC

MSC

RadiolinkMeasurements

ActiveChannelPreprocessing

HOdetection

HOcandidatecellevaluation

HOmanage-ment

BTS

RadioMeasurementsData Compression

RadioMeasurementsData Decompression

EN_MEAS_COMPRESSION

YES

NO

Figure 2.3-1: Assignment of HO functions in the ALCATEL BSS.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.

2.3.2 Specific cases of application

The handover preparation applies both for TCH and SDCCH , i.e. it uses the same messages andparameters. Whenever a different handling is necessary, it is indicated in the text. These few casesare :- counting of free channels and load of cells (section 3.2.3),- number of frames in reporting period (102 for SDCCH, 104 for TCH),- weighting in case of DTX on TCH/FS. DTX is not allowed on SDCCH (refer to [20]).- inhibition of SDCCH handover when SDCCH_COUNTER is running (see section 3.2.1.2).- inhibition of SDCCH handover in case of GPRS redirection procedure.- inhibition of better cell handovers from SDCCH to SDCCH except for the cause power budget (seesection 3.2.2.1.1.3). In case of directed retry from SDCCH to TCH on handover alarms the better cellhandover causes are not inhibited.

However it does not apply to all the channels in a multislot configuration. In fact, in this case thehandover preparation applies only to the main channel. The handover preparation takes only intoaccount the measurements reported for the main channel.

2.3.3 Handover detection

Note first that this process may be sometimes named ’HO threshold comparison’.

The process is achieved in the BSC.

Each time a set of preprocessed (averaged) measurements is available, this process checks whethera handover is needed. If the need for a handover is detected, the target cell evaluation process istriggered.

In case of a handover alarm, the handover detection process gives to the cell evaluation process :- the preferred target cell layer : lower, upper or none- the raw candidate cell list, which can be either all neighbours, or the subset which verify thehandover causes (plus other specific cells in particular cases). With each cell is given one of thehandover causes which have been verified.

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

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

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

The table 2.3-1 represents the four handover categories.

Handover Cause -> Situation of Emergency Existence of Better conditionsIntracell handover Emergency Intracell Handover Better Zone HandoverIntercell handover Emergency Intercell Handover Better Cell Handover

Table 2.3-1 : Categories of handover

The following paragraphs detail the different categories of handover according to the context ofapplication (inter or intracell) and the handover cause.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.

2.3.3.1 Emergency intercell handovers

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

2.3.3.1.1 Quality and Level causes

The aim of these causes is to keep the call going when the radio link is degrading otherwise the radiolink failure might be detected and the call released. These causes wait generally for the power controlprocess to increase the BS and MS power to their maximum values, except for the causes specific tomicrocellular environment.Handover on "too low level" is used to avoid situations where the interference level is low, while theattenuation is quite high. These conditions may appear for example in big city streets which enable aline of sight propagation from the BTS antenna. There is in this case a risk of abrupt qualitydegradation, if the MS moves away from the line of sight street.

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

2.3.3.1.2 Too long MS-BS distance cause

This cause is used when a dominant cell provides a lot of scattered coverages inside other cells, dueto propagation conditions of operational network. These spurious coverages have the consequenceof producing a high level of co-channel interference probability ([24]).

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

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

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

2.3.3.1.3 Too short MS-BS distance cause

This cause is used for handovers from an extended outer cell (the MS comes closer to the inner-outercell limit).

2.3.3.1.4 “Consecutive bad SACCH frames” and “level dropping under high threshold”

"Bad SACCH frames" and "level dropping under high threshold" are provided to support the rapidlyvarying radio conditions of microcellular environment (e.g. street corner effect). In order to have asufficient reaction time these causes are independent of the power used by the MS or BTS.

2.3.3.2 Better cell handovers

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

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



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.

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

2.3.3.2.1 Power budget cause

In this case, there is another cell with a better power budget i.e. the link quality can be improved ormaintained with a reduced transmission power of both the MS and the BTS. The radio link is notdegraded but there is the opportunity to decrease the overall interference level by changing theserving cell of the given MS.In conjunction with power control it presents the advantage to keep the interference as low aspossible, since it minimises the path loss between the BTS and MS.

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

The power budget calculation is described in details in appendix A.This power budget gives the difference in path loss between the current cell and the adjacent cellsreported by the mobile.When PBGT(n) is greater than 0, then the path loss from cell n is less than the path loss from theserving cell and thus the radiated power in the downlink direction, and therefore in the uplinkdirection as well, will be lower in cell n than in the current cell.

However it would not be advisable to hand over the MS to another cell as soon as PBGT is greaterthan 0, because the MS would probably oscillate between the two adjacent cells as the propagationconditions vary. A hysteresis mechanism is implemented to avoid this undesirable effect.

The MS may be handed over from the serving cell indexed 0 to a neighbour cell indexed n only if thepower budget exceeds the handover Margin(0,n). The handover Margin(0,n) can be modifiedaccording to the traffic situation in the serving cell and the neighbour cell n. In this way, power budgethandover can be delayed towards a loaded cell and traffic load handover can be triggered from aloaded cell (see section 2.3.3.2.4.). Once the MS is handed over, the same algorithm is applied in thenew cell, and a new PBGT is computed (which will be close to the opposite value of PBGT in the oldcell) and compared to a new HOMargin. (Thus, the global hysteresis (from cell 0 to cell n and back tocell 0) is the sum of the two HOMargins).

However, It is still possible that a ping-pong mechanism is created by different handover causes, forinstance a handover may be triggered towards a neighbour cell for bad quality, but in the neighbourcell, a handover back may be triggered for power budget reasons. In order to avoid this, an additionalanti-ping-pong mechanism is implemented in the power budget calculation. It enables to penalise fora certain time the cell on which the call has precedently been (see Appendix A).

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

In multiband cell environment, the mobile can operate in a different band than the frequency band ofthe BCCHs. This can lead to circular ping-pong handovers from the inner zone if the new band isDCS 1800 or to the impossibility to trigger PBGT handovers from the inner zone if the preferred bandis GSM 900.To avoid this problem, when the MS is in the inner zone of a multiband cell, it may be handed overfrom the serving cell indexed 0 to a neighbour multiband cell indexed n only if the power budgetexceeds the handover Margin(0,n) plus the offset handover margin which allows to handicap orfavour the PBGT (In the inner zone, the cause “power budget” is only checked between multibandcells, in a way to maintain the MS in the preferred band).



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.

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

2.3.3.2.2 Better cell cause specific to hierarchical network

In a hierarchical cell environment, advantage can be taken of the upper layer to separate the slowmoving MS from the fast moving MS.The detection of a short residence time in a lower layer cell will enable to detect fast moving mobilesand to hand them over to the upper layer.Additionally, it is possible that GSM Phase 1 slow moving mobiles get connected on the umbrella cell,e.g. for signal level reasons.For this reason, handovers are triggered towards neighbour lower layer cells, for slow mobiles whichare in the coverage area of the lower layer.

Therefore, the algorithms will insure that most of the slow moving mobiles are handled in the lowerlayer, while the fast moving mobiles are handled in the upper layer.With this policy, signalling overhead and speech breaks due to repetitive handover are avoided forfast moving MS.

Another advantage of the hierarchical cell structure is that the umbrella cell can offer a number ofoverflow channels, for calls which are queued in the lower layer (see directed retry).This allows a much better usage of the traffic capacity of the lower layer cells, when they have 1 or 2TRX, at a constant grade of service (typically 2% blocking).

On the other hand, frequencies on the upper layer can not be reused within a small range and willtherefore be a critical resource in hierarchical cell structures. Therefore, the load of the umbrella cellmay be a critical problem and a mechanism is forecast to stop handovers into the upper layer when itbecomes overloaded.This cause is inhibited for handover from SDCCH to SDCCH.

2.3.3.2.3 Preferred band cause

If cells of different frequency bands (GSM900 and DCS1800) coexist in the same network, anoperator can define a preferred band (PREFERRED_BAND parameter adjustable on a per BSSbasis) where the multiband mobiles (mobiles with the both frequency bands capability) should betransferred in case of too much traffic load in the classical band (the opposite of the preferred band)and no high load in the preferred band.

This is achieved by monitoring the traffic load of the cells which use the classical band and thepreferred band. If a multiband mobile is connected to a cell in the classical band where a specificcondition on the traffic load is verified, and if this mobile receives good signal level from oneneighbour cell which uses the preferred band and where the traffic load is considered as not high, thepreferred band cause will be verified for this mobile.

Then, an intercell multiband handover will be performed towards the neighbour cell. The onlyrequirement for this handover is that the serving cell uses the classical band and the target cell, thepreferred band.This cause is inhibited for handover from SDCCH to SDCCH.

2.3.3.2.4 Traffic handover

The principle of this handover is to reduce the size of the serving cell when it is high loaded relativelyto a low loaded cell.When the mobile moves away from the BTS, the power budget will increase and a better cellhandover will be triggered earlier.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.

It is recommended to inhibit Traffic handover towards 1 TRX cells. These cells do not have enoughresources to receive incoming handovers due to congestion of neighbour cells. Moreover because ofthe 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.

2.3.3.2.5 General capture handover

In hierarchical network where cells use different frequency bands, a general capture handover isrequired to manage, on a per cell adjacency basis, the possibility for the mobiles to be captured. Thisis needed in order to synchronise the capture from a macrocell to a microcell (as described in2.3.3.2.2) or from the same macrocell to another cell of preferred band (as described in 2.3.3.2.3).This general capture handover takes into account the load in the serving and in the target cell.This cause is inhibited for handover from SDCCH to SDCCH.

2.3.3.3 Emergency intracell handovers

The causes specifics to emergency intracell handovers are: “too high interference level”, “too lowlevel in the inner zone”.

Emergency handover is triggered for intracell application when the radio link is deemed to suffer ahigh level of interference. In this case, the channel assigned to the call is changed for anotherchannel in the same cell, on which the measured interference level is the smallest possible.

In the case of concentric cell or multiband cell environment, emergency intracell handovers concernhandovers from the inner to the outer zone of the same cell (they are called interzone handovers) aswell as handovers performed within one zone (they are called intrazone handovers).

2.3.3.4 Better zone handovers

For concentric cells, the "outer zone uplink and downlink level too high" cause forces an intracellhandover from an outer zone TCH to an inner zone TCH. This handover is considered as interzonehandover.Then the MS can operate on frequency channels with lower BS and MS maximum powers. If theinner zone is congested, the MS will stay on the outer zone.

For multiband cells, this same cause forces an intracell handover from an outer zone TCH in theclassical band to an inner zone TCH in the preferred band.

The handover detection is made on signal levels coming from the serving cell and possibly from theneighbour cells.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.

2.3.4 Handover candidate cell evaluation

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

2.3.4.1 Cell ordering according to target layer and target band

In hierarchical or multiband environment, cells are characterised by the layer they belong to or/andthe frequency band they use. The candidate cell evaluation process takes into account thesecharacteristics in the candidate cell ordering.

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

After this possible distinction, in each part of the list, the candidate cell evaluation sorts the candidatecells according to the parameter PRIORITY(0,n) (parameter on line changeable from the OMC-R).The cells having the highest priority are put in the first place of the list. They are followed by the cellshaving lowest priorities. The PRIORITY(0,n) is only used when the flag EN_PRIORTY_ORDERING isset to enable.

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

The cell evaluation function (see section 3.2.3.) is then applied to the different candidate cell listsdefined from the preferred layer indication, the PRIORITY(0,n) parameter and the frequency band ofthe serving cell (only in case of emergency handover).

2.3.4.2 Filtering process

The filtering process allows to filter out cells from the target list before sending them to the ORDER orGRADE evaluation process.It can be enabled/disabled on-line on a per cell basis from the OMC-R with the flagEN_PBGT_FILTERING.The candidate cells are filtered on their power budget in relation to a handover margin thresholdbased on the handover cause.

2.3.4.3 Candidate cell ranking

Two types of cell evaluation algorithms can be used : ORDER and GRADE.ORDER and GRADE are two different methods of cell ranking. They both consist in giving a mark or’figure of merit’ to each candidate cell.

The basic differences between ORDER and GRADE are that :

with ORDER

- The candidate cell evaluation process interacts with the handover detection by use of causedependent handover margins.

- The candidate cell evaluation process takes into account the number of free TCH in the candidatecells.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.

with GRADE, :- The candidate cell evaluation process does not interact with the handover detection.- The candidate cell evaluation process takes into account the relative load of traffic channels in the

candidate cells.

The type of cell evaluation is chosen by the operator on a (serving) cell basis and is provided to theBSC with the parameter CELL_EV (see [5])

Each algorithm uses the following parameters to compare candidate cells:

ORDER GRADEPower budget X XNumber of free TCH/FS X(1)Cell load (%) X(1)

Emergency handover type XTable 2.3-2: Comparison of candidate cell evaluation algorithms

(1) The number of free TCH in the calculation of ORDER and the cell load in the calculation ofGRADE will only be used in case of an internal candidate cell and when the flag EN_LOAD_ORDERis set to ENABLE. Otherwise, there is no offset due to load information in the candidate cellevaluation.

Note : When the preferred candidate cell belongs to the serving BSC, the BSC can autonomouslydecide and execute intra-BSC HO. But if the preferred cell is outside the BSC (or in any casedepending on the system parameter EXT_HO_FORCED set by the operator) the BSC sends its list ofpreferred cells to MSC for inter-BSC HO decision and execution. This is the task of the entityhandover management (refer to [14]).

2.3.5 Inhibition of handover

The operator has the possibility to inhibit selectively the different handover causes via O&Mcommands on a cell basis.

Inhibition and control of handover management

The following flags are set per cell and are on-line changeable.These flags are used by the handover management entity(see [14]). They are not used by thehandover preparation function , except for HO_INTERCELL_ALLOWED andEN_INTRACELL_REPEATED. They are mentioned only for information with respect to the flagsdescribed in the next paragraph.

The following flags can be used to inhibit and control the execution of a handover in the BSC :- HO_SDCCH_INHIBIT : inhibition of all outgoing handovers on SDCCH (external and internal)- HO_INTERCELL_ALLOWED : enable/disable intercell handover,- EXT_HO_FORCED : forcing of all internal intercell BSC handovers (TCH and SDCCH) to be

external handovers (i.e. controlled by the MSC).- HO_INTRACELL_ALLOWED : inhibition of all intracell (BSC internal) handovers (TCH and

SDCCH). This flag does not control the inhibition of interzone handover (see below).- EN_IC_HO : inhibition of all incoming handovers- EN_INTRACELL_REPEATED : inhibition of repetition of intracell handover , by triggering an

intercell handover with cause "Quality too low".

Inhibition of the handover preparation

The following flags can be used to inhibit the detection of a handover cause.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.

- HO_INTERCELL_ALLOWED : enable/disable intercell handover causes,- EN_INTRACELL_REPEATED : enable/disable repetition of intracell handover causes,- EN_RXQUAL_UL : enable/disable too low quality uplink cause,- EN_RXQUAL_DL : enable/disable too low quality downlink cause,- EN_RXLEV_UL : enable/disable too low level uplink cause,- EN_RXLEV_DL : enable/disable too low level downlink cause,- EN_PBGT_HO : enable/disable power budget cause,- EN_DIST_HO : enable/disable too long MS-BS distance cause,- EN_INTRA_UL : enable/disable too high interference uplink cause,- EN_INTRA_DL : enable/disable too high interference downlink cause,- EN_MCHO_H_UL : enable/disable level uplink, high threshold, microcell cause,- EN_MCHO_H_DL : enable/disable level downlink, high threshold, microcell cause,- EN_MCHO_RESCUE : enable/disable microcell to macrocell handover on missing MS

measurement reports,- EN_MCHO_NCELL : enable/disable upper to lower layer handover cause.- EN_PREFERRED_BAND_HO : enable/disable multiband handover cause.- EN_BETTER_ZONE_HO : enable/disable too high level on the uplink and the downlink, outer zonecause.- EN_TRAFFIC_HO(0,n) : enable/disable traffic HO cause from the serving cell to the cell n.- EN_GENERAL_CAPTURE_HO : enable/disable general capture handover cause.

When these flags are set to DISABLE, the corresponding handover alarms are not checked by thehandover detection function.

For the flags controlling handover cause :- If the flag is set to "ENABLE", the checking of the handover cause is enabled.- If the flag is set to "DISABLE" the checking is disabled.

Note : For the multiband handover cause, the enabling of the flag EN_PREFERRED_BAND_HOdoes not imply automatically the execution of multiband handovers. It depends also on the flagEN_INTERBAND_NEIGH used on a per BSS basis (see [19]).

The flags are per cell and on-line changeable, this means that for each cell the operator can enable ordisable some handover causes without releasing active calls in the cell.Consistency checks are performed by the OMC-R, in order to maintain the overall coherence of allflags with the type of the cell.

Particular cases for concentric or multiband cells

In the case of concentric or multiband cells, a handover cause due to high interference level (causes15 or 16, see 3.2.2) triggers an intrazone or an interzone handover. An intrazone handover is aparticular case of intracell handover.

A handover cause due to too low level in the inner zone (causes 10 or 11) or the better zone cause(cause 13) triggers an interzone handover (see section 3.2.2.1.2). An interzone handover is aparticular case of intracell handover.

The two HO causes (10, 11) cannot be enabled or disabled individually. These causes are enabledand disabled when the parameter CELL_PARTITION_TYPE = CONCENTRIC and = NORMALrespectively (see sections 2.2 and 3.2.2). Moreover the HO cause 13 must not be disabled in case ofallocation in the inner zone during Normal Assignment (the flag EN_BETTER_ZONE_HO should notbe looked at when deciding whether the MS should go to the inner zone or outer zone).

Therefore, HO_INTRACELL_ALLOWED flag does not control the enabling/disabling of the interzonehandover, but only of the intrazone handover (or interzone handover causes 15 or 16).



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.

In the same way, the flag EXT_HO_FORCED has no influence on the interzone handover operation.Finally , the flag EN_INTRACELL_REPEATED does not control the repetition of the interzonehandover.

2.3.6 Functional diagram of Handover preparation

The figure 2.3-2 is the SADT diagram of the handover functions in the BSC. This diagram is just afunctional description. It does not constrain the implementation.

The BSC receives raw measurement data from the BTS in the message MEASUREMENT RESULT ifEN_MEAS_COMPRESSION=DISABLE or compressed measurement data in the messagePREPROCESSED MEASUREMENT RESULT every SACCH multiframe period (see radio linkmeasurements, ref. [8] and Radio measurements data processing, ref[20]). The BSC pre-processesthat data to detect HO threshold conditions. The preprocessed measurement reports are thereforegenerated internally by the BSC which uses them also for candidate cell evaluation.

The Active Channel Preprocessing function is not specified in this document (refer to [20]). That iswhy it is not represented in bold type.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

Figure 2.3-2 : SADT diagram of handover functions in the BSC

Active channelpreprocessing

Handoverdetectionaveraged measurements

for handover detection

P

MS & BSparameters

HO candidatecell evaluation

LOADfactor(n), FREEfactor(n), AV_LOAD

CELL_EV

candidate cell evaluation parameters

T_FILTER

Candidate cells list,HO cause

HO and DRenabling flags

HO detection parameters

HO cause,raw cell list,

"Enable directed retry" EN_LOAD_ORDER

MS speed discrimination parameters

PREF_LAYER

cellconfigurationparameters

T_HCP

"Start T_HCP"

Traffic_load(n)

“MS Zone Indication Request”

“MS Zone Indication ACK (ZONE)”

"Enable GPRS redirection"



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

Flows descriptionThe description is done at BSC level (see Figure 2.3-2).

Input flows

- FREEfactor(n), LOADfactor(n), AV_LOAD, t(n): respectively correction factor of ORDERdepending on free level of cell n, correction factor of GRADE depending on load of cell n, averagedtraffic load (refer to [16]) and absolute number of free TCH in the cell n. These flows are BSCinternal.

- Traffic_load(n): situation of the traffic in the cell n (refer to [ 16]).

- Averaged measurements for handover detection :* AV_RXQUAL_UL_HO, AV_RXQUAL_DL_HO, AV_RXLEV_UL_MCHO,* AV_RXLEV_UL_HO, AV_RXLEV_DL_HO, AV_RXLEV_DL_MCHO,* BS_TXPWR, MS_TXPWR, AV_RANGE_HO, AV_RXLEV_PBGT_DR,* AV_BS_TXPWR_HO, AV_BS_TXPWR_DR,* AV_RXLEV_PBGT_HO, AV_RXLEV_NCELL(n), AV_RXLEV_NCELL_BIS(n).* AV_RXLEV_NCELL_DR(n), n=1..BTSnum.* BFI_SACCH

Control flows

- Cell configuration parameters : CELL_DIMENSION_TYPE, CELL_LAYER_TYPE,CELL_PARTITION_TYPE, CELL_BAND_TYPE, ZONE_TYPE, CELL_RANGE,FREQUENCY_RANGE.

- MS and BS parameters : Maximum and minimum MS/BS powers allowed in the cell :MS_TXPWR_MAX, BS_TXPWR_MAX, MS_TXPWR_MIN, BS_TXPWR_MIN,Maximum MS power in the inner zone of a concentric or multiband cell :MS_TXPWR_MAX_INNER,Maximum BS power in the inner zone of a concentric or multiband cell :BS_TXPWR_MAX_INNER.

- T_FILTER : Time after which a “no alarm” message (an alarm message with no candidate cell, seesection 3.3.) is sent to the handover management entity, if no new alarm has been detected whilstrunning.

- T_HCP : time during which penalty PING_PONG_HCP is applied to the preceding cell (cause 12);time during which penalty is applied to the preceding inner zone (cause 13).

- P : MS classmark (maximum MS power) for the concerned frequency band(s) (GSM900, DCS1800,DCS1900). In case of multiband mobiles, both MS classmark for GSM900 and MS classmark forDCS1800 band are considered.

- Candidate cell evaluation parameters :* MS_TXPWR_MAX(n) : n=1..NBR_ADJ,* HO_MARGIN(0,n) : n=1..NBR_ADJ,* HO_MARGIN_LEV(0,n) : n=1..NBR_ADJ,* HO_MARGIN_QUAL(0,n) : n=1..NBR_ADJ,* HO_MARGIN_DIST(0,n) : n=1..NBR_ADJ,* PRIORITY(0,n) : n=1..NBR_ADJ,* EN_PRIORITY_ORDERING,* OFFSET_HO_MARGIN_INNER,* RXLEV_MIN(n) : n=1..NBR_ADJ,* LINKFACTOR(0,n) : n=1..NBR_ADJ,* T1 thresholds : LOADlevel_i i=1..5, T1 factors : LOADfactor_i i=1..5,



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

* T2 thresholds : FREElevel_i i=1..5, T2 factors : FREEfactor_i i=1..5,* NBR_ADJ : number of adjacent cells.* identity (BSIC + BCCH ARFN) of the preceding cell if internal to the BSC* EN_SPEED_DISC : flag enabling the sending of fast MS to the umbrellas* EN_PBGT_FILTERING : flag enabling/disabling the filtering process* L_LOAD_OBJ : maximum load on the umbrella to hand over a fast moving mobile* PING_PONG_HCP : handicap applied to the preceding cell for power budget calculation orhandicap applied to the preceding inner zone in the cause 13.See definition of these parameters in section 3.2.2.

- CELL_EV : indicator of GRADE/ORDER handover (cell evaluation indicator).

- "Enable directed retry" : indication to the handover preparation to start the preparation for directedretry.

- "Enable GPRS redirection" : indication to the handover preparation to start the preparation forGPRS redirection.

- “MS zone Indication Request” : Request from the allocation function (refer to [16]) to the handoverpreparation for determining the zone location of the mobile in a concentric or multiband cell (seesection 3.1.1) in case of allocation during Normal assignment in the concentric or multiband cell.

- HO and DR enabling flags : HO_INTERCELL_ALLOWED, EN_INTRACELL_REPEATED,EN_DR, EN_FORCED_DR, EN_EXT_DR,EN_RXQUAL_UL, EN_RXLEV_UL,EN_RXQUAL_DL, EN_RXLEV_DL,EN_DIST_HO, EN_PBGT_HO,EN_INTRA_UL, EN_INTRA_DL,EN_MCHO_H_UL, EN_MCHO_H_DL, EN_MCHO_RESCUE,EN_MCHO_UL, EN_MCHO_DL,EN_MCHO_NCELL,EN_PREFERRED_BAND_HO,EN_GENERAL_CAPTURE_HO,EN_TRAFFIC_HO(0,n),EN_BETTER_ZONE_HOEN_GPRS_REDIRECTION.

- EN_LOAD_ORDER : flag controlling the use of the FREEFACTOR and LOADFACTOR in thecalculation of candidate cell list (ORDER and GRADE modes).

- HO detection parameters :* RXLEV_UL_ZONE, RXLEV_DL_ZONE, ZONE_HO_HYST_UL, ZONE_HO_HYST_DL,* L_RXQUAL_UL_H, L_RXLEV_UL_H, RXLEV_UL_IH,* L_RXQUAL_DL_H, L_RXLEV_DL_H, RXLEV_DL_IH,* U_TIME_ADVANCE, L_TIME_ADVANCE,* N_BAD_SACCH,* L_RXLEV_CPT_HO(0,n), n=1..NBR_ADJ,* U_RXLEV_UL_MCHO, U_RXLEV_DL_MCHO,* L_RXLEV_NCELL_DR(n), n = 1..NBR_ADJ,* EN_BI-BAND_MS(n),* EN_GPRS(n),* OUTDOOR_UMB_LEV(0,n), n ### { neighbour umbrella cells}* PREFERRED_BAND : Frequency band type preferably used by multiband mobiles.

* MULTIBAND_TRAFFIC_CONDITION : Condition on traffic load in the serving cell for amultiband handover.* CAPTURE_TRAFFIC_CONDITION : Condition on traffic load in the serving cell for a generalcapture handover.* NEIGHBOUR_RXLEV(0,n),



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

* RXLEV_LIMIT_PBGT_HO,* DELTA_INC_HO_margin, DELTA_DEC_HO_margin.

- Speed discrimination parameters and variables* MS_SPEED* PREC_LAYER_TYPE* C_DWELL* L_LOAD_OBJ, H_LOAD_OBJ* MIN_DWELL_TIME, MIN_CONNECT_TIME* L_MIN_DWELL_TIME, H_MIN_DWELL_TIME, DWELL_TIME_STEP

Internal flows

- Candidate cell evaluation input* HO cause* raw cell list of potential candidate cells* PREF_LAYER : preferred target cell layer

- "Start T_HCP" : This timer is started in the target cell after an incoming internal handover. Thistimer is also started after an intracell handover in a concentric cell when the preceding zone is theinner zone.

Output flows

- Candidate cells list (with the MS Zone Indication for each concentric cell of the candidatecells list), HO cause: provided to the Handover management entity.

- “MS Zone Indication ACK(ZONE)” : Indication to the allocation function (refer to [16]) of the zonein the concentric or multiband cell where the mobile is situated.

2.4 Directed retry preparation

2.4.1 System aspects

The directed retry consists in an SDCCH to TCH intercell handover during the call set-up process.The directed retry is triggered when given radio conditions are met and the serving cell is congested.The handover to TCH in another cell reduces the call set-up time (queuing phase) and allows thesharing of resources from one cell with another, thus overcoming traffic load unbalance.In this release of the ALCATEL BSS, the directed retry can be internal or external to the BSS (see [9]and [10]).

The start and stop of the directed retry preparation are described in section 3.3.1.1.

The directed retry may be performed :- either on handover alarms : If a handover alarm is detected during queuing, and the candidate cell

evaluation process indicates at least an internal or external cell, then the BSS will perform adirected retry .

- or on alarm of forced directed retry : If during queuing, an internal or external neighbour cell isreported with a sufficient level and has free TCH, then the BSS will perform a directed retry .The expression "Forced directed retry" refers to this case, because the radio conditions in theserving cell do not represent a need for handover. The cause which leads to forced directed retry isassimilated to a "better condition cause" in the handover preparation.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

2.4.2 Functional description

The directed retry preparation is supported :- by the same processes as the handover preparation for directed retry on handover alarms,- by a specific condition in the alarm detection process (new cause pertaining to forced directed retry)and a specific candidate cell list evaluation process for forced directed retry.

This is depicted in figure 2.4-1.

Directed Retry preparation

DetectionCandidate cell list evaluation

Intercell Emergency Handover Causes (7,17,18,2,4,3,5,6,22)

ORDER/GRADEevaluationprocess

Intracell HandoverCauses (15, 16)

Priority checking

Interzone Emergency Handover Causes (10, 11)

evaluationprocess forforced directedretry

Intercell Better Cell Handover Causes (21, 14, 12, 23)

ORDER/GRADEevaluationprocess

Interzone Better ZoneHandover Cause (13)

Forced DirectedRetry Cause (20)

Figure 2.4-1 : Functional diagram of directed retry preparation function

The detection process for directed retry consists in the checking of the handover alarms and of theforced directed retry alarm.

If an alarm for forced directed retry is raised, then the target cell evaluation is performed by thecandidate cell evaluation process for forced directed retry.For all other alarms, the target cell evaluation is performed by the candidate cell evaluation processfor handover (see section 3.2.3.).Note : The intracell handover alarms (interzone or due to interference) are ignored by the cellevaluation process.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

For further details about this process and the alarm priority order, refer to section 3.2.2.2.

2.4.3 Directed retry on handover alarms

The preparation of directed retry on handover alarms is performed by the handover preparationfunction. All the processes of this function operate in the same way as for preparation of SDCCH orTCH handover at the exception of the candidate cell evaluation process.

The candidate cell evaluation process (see section 3.2.3.) looks for target cells so as to do an SDCCHto TCH handover.TCH load (i.e. Freelevels and Loadlevels related to TCH) in neighbour cells may be used for targetcell evaluation and ranking (the TCH load is not known in case of external cells).

Note : in case of handover preparation, the candidate cell evaluation process looks for target cells soas to do a SDCCH handover. The SDCCH load is not taken into account (see section 3.2.3).

2.4.4 Forced directed retry

The preparation of forced directed retry is composed of two processes :- forced directed retry detection,- candidate cell evaluation.

The forced directed retry detection requires specific preprocessed measurements(refer to [20]).The detection is performed every SACCH measurement reporting period when preprocessedmeasurements are available.The averaged received levels of all neighbour cells are compared to a threshold. If one or severalcells are found with a received level higher than the threshold, an alarm of forced directed retry israised : high level in a neighbour cell for forced directed retry. This cause is included in the "bettercondition causes" of the handover preparation.

When detected, this alarm is sent , with the list of internal and external cells fulfilling the condition, tothe candidate cell evaluation process for forced directed retry if there is no handover alarm raised atthe same time. A handover alarm raised at the same time is prior and is sent to the candidate cellevaluation process (see section 3.2.3.).

Then, the candidate cell evaluation process looks for cells :a. where the MS can communicate,b. where the received level at MS is higher than a given threshold,c. and which have a minimum number of TCH channels free (in case of internal cell).The condition b. allows the control of the interference level in the network.The condition c. is a means to forbid "retry traffic" from a congested cell to a neighbour cell if theneighbour cell has less than a minimum number of channels free. This condition controls the amountof "retry traffic" and therefore the additional interference generated by this type of traffic.

2.4.5 Inhibition of directed retry

Outgoing directed retryThe directed retry from a serving cell is inhibited by an O&M flag :

EN_DR : DISABLE = directed retry disabled,ENABLE = directed retry enabled.

This flag is settable on a per cell basis and is on-line changeable.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

The flag EN_DR is handled by the handover management entity (see [14]) and not by the directedretry preparation function (see section 3.3.1.1).

The external directed retry from a BSC is inhibited by the flag EN_EXT_DR.

EN_EXT_DR: DISABLE = external directed retry disabled,ENABLE = external directed retry enabled.

The flag EN_EXT_DR is only relevant when EN_DR = ENABLE.The flag EN_EXT_DR is handled by the handover management entity (see [14]]) and not by thedirected retry preparation function (see section 3.3.1.1).

When EN_DR = ENABLE, the type of directed retry is determined by the combination of all inhibitionflags for handover (see section 2.3.5) and forced directed retry detection :

The forced directed retry is enabled/disabled on a per cell basis with the O&M flag EN_FORCED_DR.EN_FORCED_DR : DISABLE = forced directed retry disabled.

ENABLE = forced directed retry enabled.

The flag EN_FORCED_DR is only relevant when EN_DR = ENABLE as the detection of forceddirected retry may operate only when the directed retry function is enabled. On the opposite, thehandover alarm detection operates whatever the value of EN_DR flag as this detection is used notonly for directed retry but also for SDCCH handover.

Interaction with handover inhibition flags :- The flags EXT_HO_FORCED and HO_SDCCH_INHIBIT are not checked by the directed retrypreparation function.- The flag HO_INTERCELL_ALLOWED applies to the cause of forced directed retry as for the otherhandover causes (see section 2.3.5).

Incoming directed retry

### Forced directed retry : the incoming retry traffic in a cell n can be forbidden by setting theparameter FREElevel_DR(n) to its maximum value i.e. 255 (see section 3.3.3).

### Directed retry on handover alarms : the incoming retry traffic in a cell can be forbidden by settingthe parameters FREEfactors_i and LOADfactors_i to their minimum values.

2.5 GPRS redirection preparation

2.5.1 System aspects

The GPRS redirection consists in a cell change order to a MS connected to a cell not supportingGPRS. The GPRS redirection is enabled with the flag EN_GPRS_REDIRECTION (see ref [6]). TheGPRS redirection is triggered when given radio conditions are met and the target cell is supportingGPRS.

The start of the GPRS redirection preparation is described in section 3.4.1.1.

The GPRS redirection is performed on an alarm of GPRS redirection : If during SDCCH period, aneighbour cell is reported with a sufficient level and is supporting GPRS, then the BSS will perform aGPRS redirection.The cause which leads to GPRS redirection is assimilated to a "better condition cause" in thehandover preparation.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

2.5.2 Functional description

The GPRS redirection preparation is supported by a specific condition in the alarm detection process(new cause pertaining to GPRS redirection) and a specific candidate cell list evaluation process forGPRS redirection.

The detection process for GPRS redirection consists in the checking of the GPRS redirection alarm.

If an alarm for GPRS redirection is raised, then the target cell evaluation is performed by thecandidate cell evaluation process for GPRS redirection.

2.5.3 GPRS redirection

The preparation of GPRS redirection is composed of two processes :- GPRS redirection detection,- candidate cell evaluation.

The GPRS redirection detection requires the same preprocessed measurements as for forceddirected retry(refer to [20]).The detection is performed every SACCH measurement reporting period when preprocessedmeasurements are available.The averaged received levels of all neighbour cells are compared to a threshold. If one or severalcells supporting GPRS are found with a received level higher than the threshold, an alarm of GPRSredirection is raised : high level in a neighbour cell for GPRS redirection. This cause is included in the"better condition causes" of the handover preparation.

When detected, this alarm is sent , with the list of internal and external cells fulfilling the condition, tothe candidate cell evaluation process for GPRS redirection.

Then, the candidate cell evaluation process sorts cells :a. where GPRS is supported,b. and where the received level at MS is higher than a given threshold.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

3. DYNAMIC BEHAVIOUR

3.1 Functions linked to handover preparation

3.1.1 Concentric cell and multiband cell

A concentric cell is identified in the BSS by setting its attached flag CELL_PARTITION_TYPE toCONCENTRIC.

A multiband cell is identified in the BSS by setting its FREQUENCY_RANGE to GSM-DCS(CELL_PARTITION_TYPE is forced to concentric).

Each frequency carrier of the cell is allocated to either the inner zone or the outer zone. Thisallocation is indicated by the flag ZONE_TYPE (OUTER ZONE or INNER ZONE) on a per frequencycarrier basis.Any SDCCH connection is always allocated to the outer zone (ZONE_TYPE = OUTER ZONE).

3.1.1.1 Allocation in the inner zone in case of Normal Assignment

In order to assign from the start a TCH in the zone corresponding to the MS location, the informationon the measured level gathered by the handover detection function is used.The TCH allocation function (refer to [16]) during Normal Assignment in a concentric cell or in amultiband cell will request to the handover detection function (with the indication “MS Zone IndicationRequest”, see section 2.3.6) the zone where the MS is deemed to be : inner or outer zone.If the MS is in a multiband cell and the MS is not a multiband one, the indication is always OUTER.

To this avail, the handover detection function will check all the relations in the cause "outer zone toohigh” (cause 13) except (EN_BETTER_ZONE_HO=ENABLE) using- the AV_RXLEV_UL/DL averages , if A_LEV_HO measurements have been received- the average of the RXLEV_UL/DL measurements already received.

The average of the RXLEV_NCELL(n) measurements is computed for each neighbour cell with asame window whose size is determined by the number of MEASUREMENT RESULT messageswhich have already been received since the first received MEASUREMENT RESULT message with aLayer 3 info present.As long as this number is lower than A_PBGT_HO, it is used as window to calculate these averages.When this number becomes higher than A_PBGT_HO, then A_PBGT_HO is used as window tocalculate these averages.

If the cause 13 is satisfied, then the handover detection function will answer that the MS is in theinner zone, otherwise in the outer zone with the indication “MS Zone Indication ACK(ZONE)”, seesection 2.3.6.

3.1.1.2 Allocation in the inner zone in case of incoming handover

In case of an incoming intercell handover on SDCCH a channel of the outer zone of the concentric ormultiband cell is always assigned to the mobile station.

In case of an incoming intercell handover on TCH, the MS will be handed over in the zonecorresponding to its location if the flag EN_BETTER_ZONE_HO is set to enable (ifEN_BETTER_ZONE_HO is set to disable the MS is handed over in the OUTER ZONE).For that the information on the downlink measured level of the target cell RXLEV_NCELL is used.Each time, a candidate cells list is provided to the handover management entity, it must indicate foreach concentric or multiband cell, the zone where the MS is deemed to be: inner or outer zone. If theMS is in a multiband cell and the MS is not a multiband one, the indication is always OUTER zone.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

So each time a concentric or multiband cell is in the candidate cells list, the handover detectionfunction checks the following equation in a way to determine the MS zone location in this concentricor multiband cell.

IF AV_RXLEV_NCELL(target cell) > RXLEV_DL_ZONE + ZONE_HO_HYST_DL+BS_TXPWR_MAX - BS_TXPWR_MAX_INNER, the mobile is in the inner zone

ELSE the mobile is in the outer zone.

The equation is checked using:- the AV_RXLEV_NCELL(target cell) average, if A_LEV_HO measurements have been received fromthis target cell.- the average of the RXLEV_NCELL(target cell) measurements already received from the neighbourcell target cell (if between two measurements, in which the neighbour cell is reported, a measurementcomes in, in which the neighbour cell is not reported, a 0 will be used to calculate the average).

RXLEV_DL_ZONE, ZONE_HO_HYST_DL, BS_TXPWR and BS_TXPWR_MAX_INNER are theparameters of the target concentric or multiband cell. They are available only if the intercell handoveris performed in the same BSC.

3.1.1.3 Handover in a concentric or multiband cell

For concentric cell environment, the cause "power budget" is applied in the inner zone as well as inthe outer zone.

For multiband cell environment, the cause "power budget" is applied in the inner zone as well as inthe outer zone. In the inner zone, the cause “power budget” is only checked between multiband cells,in a way to maintain the MS in the preferred band.

In order to avoid unnecessary handover alarms on SDCCH for all mobiles geographically located inthe inner zone, the handover alarms cause 13 on SDCCH (from outer zone towards inner zone) mustbe filtered by the handover preparation function.

For initiation of an intercell handover between a concentric or multiband cell (inner and outer zone)and the defined adjacent cell, the same handover criteria and handover strategies hold true as fornon-concentric cells.

The criteria for handover between the inner and outer zones is based either on the received signallevel or on the interference level (see section 3.2.2.1.2). This kind of handover is called "interzonehandover".

A handover due to interference (cause = 15 or 16) will change, when it is possible, the frequency ofthe radio channel in case of non-hopping channels.As the inner zone contains only a few frequencies, this will give the opportunity to make an interzonehandover from the inner to the outer zone in case of interference problems in the inner zone.In case of interference problems in the outer zone, the MS will always make an intrazone handover (itwill stay connected to the outer zone).In case of hopping channels an interzone handover may occur from the inner to outer zone but neverin the reverse direction (as with non-hopping channels).

Both intrazone and interzone handovers are intracell handovers.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

3.1.2 MS speed discrimination

3.1.2.1 Basic principle

The speed discrimination procedure can only be activated in a hierarchical cell environment, i.e.when the serving CELL_LAYER_TYPE = "Upper" or "Lower". It is based on the dwell time in the lowerlayer cells, either as serving or neighbour cells.

The knowledge of the speed of a MS is indicated with a flag MS_SPEED that has the values "fast","slow" and "indefinite". The value of this flag is kept for the whole call duration, once it has been set to"fast". This choice relates to the assumption that a prediction is possible on the MS speed. Wheneverthe MS moves into another cell and was not recognised "fast" at this occasion, or at a precedentoccasion, the MS_SPEED is reset to "indefinite".

The time experienced in a serving lower layer cell is kept in a counter C_DWELL (in SACCHmultiframes).

When a handover cause "power budget" is triggered, and the preceding cell was already a lower layercell, this time is compared to a threshold MIN_CONNECT_TIME.If it is found smaller than the threshold, this indicates that the MS has crossed the serving lower layercell in less than MIN_CONNECT_TIME seconds. In this case , the MS is considered to be movingfast and the handover is directed towards the upper layer preferentially.If it is found bigger than the threshold, this indicates that the MS has not yet been recognised as fastand the handover is directed towards the neighbour lower layer cell.

The handover cause power budget is used because it is assumed that in any cell environment thiscause will indicate that the MS is leaving the "better cell" zone of the serving cell, and not because ofinterference, shadowing, or street corner effect.

The MS speed discrimination can only happen when the preceding cell is already a lower layer cell,this ensures that the MS has entered the cell at its edge and not at an arbitrary position inside the cell.This would be the case after call setup, or after a handover from an umbrella cell.Because the measured dwell time in the serving lower layer cell is taken between two points locatedat the edge of the cell, the time interval can be related to the MS speed, assuming that the main roadon which fast moving mobiles are, is known beforehand.

The MIN_CONNECT_TIME shall be set to the value necessary for a fast moving car (mean speed vabout 40 km/h) necessary to travel along the cell on the main road.If there is no information available about a privileged direction of fast MS, then the

MIN_CONNECT_TIME shall be set to the value 2xCell_ Diameter

v∏ × where v represents the average

speed of fast moving mobiles.

The speed discrimination function can be enabled/disabled on a per cell basis, using a flag :EN_SPEED_DISC.If EN_SPEED_DISC is set to DISABLE, then the dwell time in a serving lower layer cell is not used todetermine if an MS is fast. Nevertheless, when the MS is on the upper layer, the dwell time in theneighbour lower layer cells is used to decide a handover to the lower layer, after a fixed period oftime.

3.1.2.2 Required parameters and variables

For each call a variable PREC_LAYER_TYPE is used to store the cell layer type of the precedingcell. It has four values : single, upper, lower, indefinite.

For each call, a variable MS_SPEED is used to store the already determined mobile speed, if any. Ithas three values : "fast", "slow" and "indefinite".



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

The initialisation of the parameters will occur at call set-up and after external handover.After internal handover, the variables MS_SPEED and PREC_LAYER_TYPE will be transferred tothe new call context, after possible modification.

For each call on the upper layer,for each neighbour lower layer cell n

a counter C_DWELL(n) measures the number of SACCH periods of monitoring the neighbourcell n over a threshold L_RXLEV_CPT_HO(0,n) (see 3.1.2.3)

each time the cell n is monitored, C_DWELL(n) is compared to threshold 2*MIN_DWELL_TIME(n)

For each call on the lower layera counter C_DWELL measures the number of SACCH periods of connection to the serving cell(see 3.1.2.3).a threshold MIN_CONNECT_TIME is used at PBGT handover to decide on the MS speed

3.1.2.3 Parameter initialisation and modification

###CELL_LAYER_TYPE = lower

After call set-up or inter-cell handoverC_DWELL = 0.After an intra-cell handover, C_DWELL is kept unchanged.

After call set-up or external handover

PREC_LAYER_TYPE = indefiniteMS_SPEED = indefinite

After an internal handover :MS_SPEED is kept to the preceding value. PREC_LAYER_TYPE is set to the precedingCELL_LAYER_TYPE (upper or lower or single). Both values are transmitted to the new call context.

Each time a MEASUREMENT RESULT is received for a call in a lower layer cellC_DWELL is incremented by 1. When it reaches the maximum value of 255, it is no moreincremented.

When a handover cause "power budget" is triggered in a lower layer celland PREC_LAYER_TYPE is lowerand the parameter EN_SPEED_DISC = ENABLE for the serving celland C_DWELL < 2*MIN_CONNECT_TIME ,

then MS_SPEED is set to "fast".

Note : C_DWELL is expressed in SACCH periods and MIN_CONNECT_TIME in seconds. Hence, anapproximation of the SACCH period to 0.5 s is made in the above equation. This will have no impacton the behaviour of the speed discrimination process.

###CELL_LAYER_TYPE = upper

After call set-up, intra-cell or inter-cell handover

for all neighbour lower layer cells n :if EN_SPEED_DISC = ENABLE

Phase 1 MS : C_DWELL(n) = (MIN_DWELL_TIME - L_MIN_DWELL_TIME)*2Phase 2 MS : C_DWELL(n) = 0

else if EN_SPEED_DISC = DISABLE



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

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

After call set-up

PREC_LAYER_TYPE = indefiniteMS_SPEED = indefinite

After external handover

PREC_LAYER_TYPE = indefiniteIf A interface cause = ‘rise to upper layer’then MS_SPEED = fastelse MS_SPEED = indefinite

After internal handoverMS_SPEED is turned to "indefinite" if it was not precedently "fast", otherwise it is kept to "fast".PREC_LAYER_TYPE is set to the preceding CELL_LAYER_TYPE (upper or lower or single) andtransmitted to the new call context.

Each time a MEASUREMENT RESULT is received for a call on the upper layer :

- Each time a measurement is received for the neighbour lower layer cell n (inMEASUREMENT REPORT), with a value RXLEV_NCELL(n) strictly above the thresholdL_RXLEV_CPT_HO(0,n), C_DWELL(n) is incremented by 1. When it reaches the maximumvalue of 255, it is no more incremented.- Each time no measurement is received or the reported level is smaller or equal to thethreshold L_RXLEV_CPT_HO(0,n), C_DWELL(n) is decremented by 1. When it reaches theminimum value of 0, it is no more decremented.

If for one neighbour lower layer cell n, C_DWELL(n) ### 2*MIN_DWELL_TIME,and the MS_SPEED was "indefinite"then MS_SPEED is set to "slow".

Remarks :

For phase 1 MS, or when EN_SPEED_DISC = DISABLE in the umbrella cell, the initialisation ofC_DWELL(n) is done in such way that they will make a handover to the lower layer, afterL_MIN_DWELL_TIME seconds, provided they are under the coverage area of a lower layer cell.This will give an efficient way to reduce the load of the umbrella cell, caused by a large proportion ofPhase 1 MS, which will camp on this cell, because it has the best received level.

For phase 2 MS and when EN_SPEED_DISC = ENABLE in the umbrella cell, the mobiles will have toreceive sufficient level from a lower layer cell during MIN_DWELL_TIME seconds before leaving theupper layer for the lower layer. The variable MIN_DWELL_TIME is modified according to the trafficload in the umbrella cell in order to enable the slow mobiles to leave more easily a loaded umbrellacell (see 3.1.3.).

The "leaky bucket" mechanism on counter C_DWELL(n) allows to do with the statistical shadowingaffecting raw level measurements : if exactly 50% of the measurements are strictly above theL_RXLEV_CPT_HO(0,n) threshold, the value of C_DWELL(n) grows, otherwise it stays at 0.The value for the threshold L_RXLEV_CPT_HO(0,n) should be equal to the measured or plannedmean signal level at the border of the lower layer cells.

The counters C_DWELL(n) only work for neighbour cells, which belong to the lower layer.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

3.1.3 Load management in hierarchical environment

In a hierarchical environment, it is very important to control the traffic load of the umbrella cells. Thereason for this is that the umbrella cell may get saturated very easily, and hence unable to assume itstwo major functionalities : handle fast moving mobiles and provide overflow channels for the lowerlayer, in order to improve the total capacity at a constant grade of service.

Therefore, a control mechanism is forecast, in order to have the averaged traffic load on the umbrellacell held between two limits L_LOAD_OBJ and H_LOAD_OBJ.

This is done by two actions :- not performing handover towards the umbrella cell for power budget cause with fast mobileswhen the umbrella is loaded (see section 3.2.2.3).- reducing the MIN_DWELL_TIME variable, so as to enable slow MS to leave more quickly theumbrella cell (see section 3.1.2. and below).

Thus, the variable MIN_DWELL_TIME is modified according to the averaging of traffic load, calledAV_LOAD (refer to [16]), on the umbrella cell (see figure 3.2-4).

Each time the averaged load on the umbrella is recalculated, AV_LOAD is compared with the valuesL_LOAD_OBJ and H_LOAD_OBJ.

If AV_LOAD > H_LOAD_OBJMIN_DWELL_TIME := max(MIN_DWELL_TIME - DWELL_TIME_STEP, L_MIN_DWELL_TIME)

If AV_LOAD < L_LOAD_OBJMIN_DWELL_TIME := min(MIN_DWELL_TIME + DWELL_TIME_STEP, H_MIN_DWELL_TIME)

The default value of MIN_DWELL_TIME will be H_MIN_DWELL_TIME.

The setting of the DWELL_TIME_STEP parameter will be made using experiences in pilot sites.It will be incorporated in the user-settable default cell profile for umbrella cells, taking advantage ofthe compromise value found between reactivity and oscillating behaviour.

Note : The umbrella load control mechanism can be disabled by setting the L_LOAD_OBJ to 0% andH_LOAD_OBJ to 100%, in this way MIN_DWELL_TIME is blocked to its current value. For settingMIN_DWELL_TIME to H_MIN_DWELL_TIME, the operation (setting L_LOAD_OBJ to 0% andH_LOAD_OBJ to 100%) must be made off-line or with no load in the cell.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

L_MIN_DWELL_TIMEH_MIN_DWELL_TIME

load in umbrella cell

100 %

H_LOAD_OBJ

L_LOAD_OBJ

start : low traffic

end : low traffic

regulation of traffic peak

DWELL_TIME_STEPFigure 3.2-4 : Traffic regulation with MIN_DWELL_TIME modified according to the traffic load



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

3.2 Handover preparation

3.2.1 General

3.2.1.1 HO preparation configuration

At BSS initialisation, the parameters of handover preparation (see control flows of SADT diagrams insection 2.3.6) are contained in the BSC database (for further details on BSS initialisation, see [12]).

Concerning the BSS reconfiguration, all the handover preparation parameters can be modified atOMC side and then provided to the concerned BSS (see messages description in [5]).

For both initialisation and reconfiguration, the algorithms are configured in the BTS by the BSC withthe message PREPROCESS CONFIGURE (see message description in [20]). This message is senton the Abis radio signalling link (see [3]) on a TRX basis.

Note : In case of TCU restart, the message is sent to the BTS (i.e. to the TRX(s) connected to thecorresponding TCU).

3.2.1.2 HO preparation enabling and disabling

Enabling

The enabling may result from :- the establishment of a new connection,- an intracell handover,- an interzone handover,- an intercell handover.

So, the specifications are the following ones :- the BSC enables the algorithms upon receipt of the ESTABLISH INDICATION message from theBTS (except in case of GPRS redirection procedure). During an SDCCH connection except during aGPRS redirection procedure, the BSC filters internally the handover alarms for a given number ofMEASUREMENT RESULT messages (defined by the parameter SDCCH_COUNTER, for furtherdetails refer to [6]).

For further details on the call establishment and handover protocol refer to [7], [9] and [10].

Disabling

- the BSC disables the algorithms whenever it initiates a channel release on the radio interface.

For further details on the call release procedure, refer to [11].

3.2.1.3 HO preparation function

The handover preparation function is completely handled by the BSC. The input parameters of thisfunction are provided by the Active channel preprocessing function every SACCH multiframe (refer to[20]).

The following sections describe the general behaviour of the handover preparation function with itstwo processes :- HO detection : see section 3.2.2,- HO candidate cells list evaluation : see section 3.2.3.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

Handover detection

A handover alarm can be detected every SACCH multiframe upon reception of the averagedmeasurements for handover detection.

Handover candidate cells list evaluation

Once a handover alarm is detected, the HO detection process sends to the HO candidate cellevaluation process the list of the MS neighbouring cells with for each of them one of the handovercauses which have been verified. It is an internal BSC action (implementation dependent).

The handover candidate cells list evaluation builds a cells list which is, according to the case and thevalue of the timer T_FILTER, sent or not to the BSC function in charge of the handover managemententity (see 3.2.4.).

The figure 3.2-1 is the SDL diagram of the HO preparation function.

Note : the event "HO parameters change" corresponds to a on-line reconfiguration (managed by thenetwork operator) of the handover parameters used for HO detection and HO candidate cellevaluation.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

Figure 3.2-1 : SDL diagram - HO preparation/BSC.- partition 1/1.

Document produced by GEODE <VERILOG (C)>

Partition 1/1

1.5

DESCRIPTION: PCHO

PROCESS PCHO/Handover_preparation/Mode_B/BSC

Page: 1

03-Feb-1995

HO thresholdcomparison

HO candidatecell evaluation

idle channel

activate HOpreparation

’init T FILTER’

active channel

active channel

HOparameters

change

active channel

deactivateHO

preparation

idle channel

preproc measfor HO

HO thresholdcomparison

’conditionoccurs?’

(Yes)

HO candidatecell

evaluation

candidate cells ,HOcause TOHO execution

’triggerT FILTER’

Wait T FILTER

(No)

active channel

wait T FILTER

HOparameters

change

Wait T FILTER

T FILTERexpiry

active channel

deactivateHO

preparation

idle channel

for HO

comparison

’conditionoccurs?’

(Yes)

HO candidatecell

evaluation

candidate cells ,HOcause TOHO execution

’restartT FILTER’

Wait T FILTER

preproc meas

HO threshold

(No)

Wait T FILTER

‘Candidate celllist changes?'

(Yes)(No)

Wait T FILTER

'restartT FILTER'



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

3.2.2 Handover detection

This process is also called ’HO threshold comparison’.

Threshold comparisons are performed for every new set of average values AV_xxx_HO (i.e. everySACCH multiframe period) to detect possible need for handover. The detection of a handover causecan be enabled/disabled by flags. For each possible handover cause a flag is foreseen.

Accordingly, HO alarms are sent to initiate the candidate cell evaluation function when a thresholdcondition occurs.

After each handover alarm, the raw list of candidate cells and the preferred target cell layer areindicated to the handover candidate evaluation process.

3.2.2.1 Handover causes

Twenty one different causes can lead the ALCATEL handover algorithm to detect a need forhandover. These causes are identified with a number that is used for performance measurementcounters

Handover causes no

Too low quality on the uplink 2

Too low level on the uplink 3

Too low quality on the downlink 4

Too low level on the downlink 5

Too long MS-BS distance 6

Several consecutive bad SACCH frames received (rescue microcell handover) 7

Too low level on the uplink, inner zone (inner to outer zone handover, concentric or multibandcell)

10

Too low level on the downlink, inner zone (inner to outer zone handover, concentric ormultiband cell)

11

Power budget 12

Too high level on the uplink and the downlink, outer zone (out. to in. zone hand., concentric ormultiband cell)

13

High level in neighbour lower layer cell for slow mobile 14

Too high interference level on the uplink 15

Too high interference level on the downlink 16

Too low level on the uplink in a microcell compared to a high threshold 17

Too low level on the downlink in a microcell compared to a high threshold 18

Forced Directed Retry 20

High level in neighbour cell in the preferred band 21

Too short MS-BTS distance 22

Traffic HO 23

General capture HO 24

GPRS redirection 25Table 3.2-1 : Handover causes

These causes can be sorted into the two categories :



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

- emergency causes : 2,3,4,5,6,7,10,11,15,16,17,18,22- better condition causes : 12,13,14,20,21,23,24,25

Section 2.3.5 describes which causes can be individually inhibited by O&M commands.

Note : the relationships between the handover cause values used on the A interface and the handovercause values used by the ALCATEL BSS are given in reference [9].

In the following, the handover causes will be detailed according to the handover categories, asdefined in 2.3.3. The recapitulation of the cell types allowed for the serving and the candidate cell foreach handover cause can be found in appendix B.

3.2.2.1.1 Intercell handover causes

The equations (HO-1) to (HO-6) and (HO-18) to (HO-25) are checked only ifHO_INTERCELL_ALLOWED = ENABLE.

3.2.2.1.1.1 Emergency intercell handover causes

The various HO causes for emergency intercell handover are :

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

In order to take into account the frequency hopping in the RXQUAL evaluation the variableOFFSET_RXQUAL_FH is introduced (for more information refer to [21]).If on the corresponding channel,

Frequency hopping is applied then OFFSET_RXQUAL_FH = Offset_Hopping_HOotherwise OFFSET_RXQUAL_FH = 0

Offset_Hopping_HO is a parameter defined on a per cell basis.

CAUSE = 2 (too low quality on the uplink)

AV_RXQUAL_UL_HO > L_RXQUAL_UL_H + OFFSET_RXQUAL_FH (HO-1)and AV_RXLEV_UL_HO <= RXLEV_UL_IHand MS_TXPWR = min(P, MS_TXPWR_MAX)and EN_RXQUAL_UL = ENABLE

Note : This handover cause can also be triggered in case of repetitive intracell handover, see section3.2.2.1.1.2

CAUSE = 3 (too low level on the uplink)

AV_RXQUAL_UL_HO <= L_RXQUAL_UL_H + OFFSET_RXQUAL_FH (HO-2)and AV_RXLEV_UL_HO < L_RXLEV_UL_Hand MS_TXPWR = min(P, MS_TXPWR_MAX)and EN_RXLEV_UL = ENABLE

In (HO-1) and (HO-2), MS_TXPWR is the last MS_TXPWR_CONF value reported by the BTS in themessage MEASUREMENT RESULT or PREPROCESSED MEASUREMENT RESULT (refer to[20]).



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

CAUSE = 4 (too low quality on the downlink)

AV_RXQUAL_DL_HO > L_RXQUAL_DL_H + OFFSET_RXQUAL_FH (HO-3)and AV_RXLEV_DL_HO <= RXLEV_DL_IHand BS_TXPWR = BS_TXPWR_MAXand EN_RXQUAL_DL = ENABLE

Note : This handover cause can also be triggered in case of repetitive intracell handover, see section3.2.2.1.1.2

CAUSE = 5 (too low level on the downlink)

AV_RXQUAL_DL_HO <= L_RXQUAL_DL_H + OFFSET_RXQUAL_FH (HO-4)and AV_RXLEV_DL_HO < L_RXLEV_DL_Hand BS_TXPWR = BS_TXPWR_MAXand EN_RXLEV_DL = ENABLE

Note : In case of concentric or multiband cell, if an MS uses a TCH which belongs to the inner zone,MS_TXPWR_MAX must be replaced by MS_TXPWR_MAX_INNER in (HO-1) and (HO-2) andBS_TXPWR_MAX must be replaced by BS_TXPWR_MAX_INNER in (HO-3) and (HO-4).

Note : The case where L_RXQUAL_XX_H + OFFSET_RXQUAL_FH > 7 corresponds in the equationsto L_RXQUAL_XX_H + OFFSET_RXQUAL_FH = 7.

Unlike the previous causes, the five following handover causes do not take into account the increaseof the MS or the BS power to its maximum.

CAUSE = 6 (too long MS-BS distance)

AV_RANGE_HO > U_TIME_ADVANCE (HO-5)and EN_DIST_HO = ENABLE

The following cause is only checked if the Cell range of the cell is set to extended_outer.

CAUSE = 22 (too short MS-BS distance)

AV_RANGE_HO ≤ L_TIME_ADVANCE (HO-23)

- L_TIME_ADVANCE : Minimum distance for handover from the extended outer zone

The three following equations are only used in microcells, i.e. the corresponding flags are set toENABLE if the cell profile is microcell (or CELL_DIMENSION_TYPE = micro) and to DISABLE for allother cell profiles.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

CAUSE = 7 (consecutive bad SACCH frames received in a microcell))

last N_BAD_SACCH consecutive SACCH frames are not correctly received (HO-20)and EN_MCHO_RESCUE = ENABLE

The cause 7 is managed with an internal BSC variable which counts the number of bad SACCHframes consecutively received :- this counter is incremented every time a MEASUREMENT RESULT or PREPROCESSEDMEASUREMENT RESULT message with BFI = 1(Bad Frame Indication) is received,- this counter is reset every time a MEASUREMENT RESULT or PREPROCESSEDMEASUREMENT RESULT message with BFI = 0 is received.The format of these two messages is given in [20].

CAUSE = 17 (Too low level on the uplink in a microcell compared to a high threshold)

AV_RXLEV_UL_MCHO(i) ### U_RXLEV_UL_MCHO (HO-18)and AV_RXLEV_UL_MCHO(i-1) > U_RXLEV_UL_MCHOand EN_MCHO_H_UL = ENABLE

In (HO-18) and (HO-19), ’i’ is the index of the last MS measurement report.

CAUSE = 18 (Too low level on the downlink in a microcell compared to a high threshold)

AV_RXLEV_DL_MCHO(i) ### U_RXLEV_DL_MCHO (HO-19)and AV_RXLEV_DL_MCHO(i-1) > U_RXLEV_DL_MCHOand EN_MCHO_H_DL = ENABLE

3.2.2.1.1.2 Forced intercell handover cause on quality

If on the uplink or on the downlink :i. either the intracell handovers are forbidden in the serving cell (i.e. EN_INTRA_UL/DL = DISABLE),ii. or the repetition of intracell handover is not allowed in the serving cell,the handover detection function will indicate an intercell handover with cause "UL/DL quality too low",so far as the conditions on power level MS/BS_TXPWR_MAX, and on the flags EN_RXQUAL_UL/DLand HO_INTERCELL_ALLOWED are fulfilled.The condition RXLEV_UL/DL=<RXLEV_UL/DL_IH is not checked in this case as it is done for a non-forced quality handover (see equations (HO-1) and (HO-3)).The priority order of UL/DL is UL (uplink) and then DL (downlink).

The repetition may be inhibited by setting the O&M flag EN_INTRACELL_REPEATED to DISABLE.

Concerning the case ii, the condition ’no previous intracell handover for this connection failed’ is givenby the function handling the call in the BSC. This condition is used to avoid repetitive intracellhandovers. If an intracell handover for a given connection was not successful (handover failure, nofree timeslot, etc...) it is not repeated when the next handover alarm occurs.If an intracell handover is still required for this connection, the handover is turned into an intercellhandover as described above. Then for the same call in the new cell, intracell handover is allowedagain.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel 3.2.2.1.1.3 Better cell handover causes

### The following cause is checked over all the neighbour cells belonging to the same layer . Itmeans that it is checked between cells whose CELL_LAYER_TYPE is single or upper and betweencells whose CELL_LAYER_TYPE is lower. This cause must not be checked between cells which usedifferent frequency band (i.e cells having different CELL_BAND_TYPE)

The cause 12 for handover from TCH to TCH and for directed retry on handover alarms from SDCCHto TCH is:If the MS is in the inner zone of a multiband cell, the cause 12 is checked over all the neighbourmultiband cells (FREQUENCY_RANGE=GSM-DCS) which belong to the same BSC as the servingcell.

CAUSE = 12 (Power budget)

If EN_TRAFFIC_HO(0,n)=ENABLE (HO-6)then PBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGIN_INNER

+ max(0, DELTA_HO_MARGIN(0,n)) (n=1...BTSnum)else PBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGIN_INNER

and AV_RXLEV_PBGT_HO ≤ RXLEV_LIMIT_PBGT_HOand EN_PBGT_HO = ENABLE

with PBGT(n) = AV_RXLEV_NCELL(n) - AV_RXLEV_PBGT_HO (HO-7)- (BS_TXPWR_MAX - AV_BS_TXPWR_HO)- (MS_TXPWR_MAX(n) - MS_TXPWR_MAX)

- PING_PONG_MARGIN(n,call_ref)

OFFSET_HO_MARGIN_INNER is only used in the inner zone of a concentric or multiband cell.

The cause 12 for handover from SDCCH to SDCCH is:

CAUSE = 12 (Power budget)

PBGT(n) > HO_MARGIN(0,n) (n=1...BTSnum) (HO-6)and AV_RXLEV_PBGT_HO ≤ RXLEV_LIMIT_PBGT_HOand EN_PBGT_HO = ENABLE

The equation of PBGT is explained in details in appendix A.

- RXLEV_LIMIT_PBGT_HO : threshold above which it is not necessary to trigger a handover onpower budget.

- AV_RXLEV_NCELL(n) : average of RXLEV_NCELL(n) over A_PBGT_HO measurements(neighbour cell(n)).

- AV_RXLEV_PBGT_HO : average of the received levels RXLEV_DL_FULL or RXLEV_DL_SUBover A_PBGT_HO measurements (serving cell).

- BS_TXPWR_MAX : max power of the BTS in the serving cell (fixed value for each BTS).- AV_BS_TXPWR_HO : Average of BS_POWER over A_PBGT_HO measurements.- MS_TXPWR_MAX(n) : max. power level the MS is allowed to use in its neighbour cell(n).- MS_TXPWR_MAX : max. power the MS is allowed to use in the serving cell.- OFFSET_HO_MARGIN_INNER: offset which allows to take account of the radio differences

between outer and inner zone (especially in case of multiband cell).



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

- PING_PONG_MARGIN(n,call_ref) is a penalty put on the cell n if :it is the immediately precedent cell on which the call has been,this cell belongs to the same BSC as the serving cell,the call has not performed a forced directed retry towards the serving cell,less than T_HCP seconds have elapsed since the last handover.In this case PING_PONG_MARGIN(n,call_ref) = PING_PONG_HCP.If the call was not precedently on cell n, or if the preceding cell was external to theserving BSS, or if the call has just performed a forced directed retry, or if the timerT_HCP has expired, then PING_PONG_MARGIN(n,call_ref) = 0

- DELTA_HO_MARGIN(0,n) is evaluated according to the traffic situation of the serving cell and theneighbour cell n (Traffic_load(n), refer to [16]) in the following way.If Traffic_load(0)=high and Traffic_load(n)=lowDELTA_HO_MARGIN(0,n)= -DELTA_DEC_HO_marginIf Traffic_load(0)=low and Traffic_load(n)=highDELTA_HO_MARGIN(0,n)= DELTA_INC_HO_marginelse DELTA_HO_MARGIN(0,n)=0where DELTA_DEC_HO_margin allows the cause 23 (traffic handover) detectionwhen the traffic in the serving cell is high and is low in the cell n.DELTA_INC_HO_margin allows to penalise the cause 12 detection when thetraffic in the serving cell is low and is high in the cell n.

Note : In the case of concentric or multiband cells, if the channel is in the inner zone (ZONE_TYPE =INNER), BS_TXPWR_MAX and MS_TXPWR_MAX in equation (HO-7) must be replaced byBS_TXPWR_MAX_INNER and MS_TXPWR_MAX_INNER respectively.If the channel is in the outer zone (ZONE_TYPE = OUTER), the formulation of equation (HO-7) is notchanged.

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

The four following equations are only checked for handover from TCH to TCH and for directed retryon handover alarms from SDCCH to TCH. For handover from SDCCH to SDCCH, they are notchecked.

### The following equation is checked if and only if CELL_LAYER_TYPE = upper (this rule isapplied at the OMC by disabling the flag EN_MCHO_NCELL when CELL_LAYER_TYPE is differentfrom ’upper’).

If the MS is in the inner zone of a multiband cell, the cause 14 is checked over all the neighbour cellswith CELL_LAYER_TYPE(n) = lower except the ones with EN_BI-BAND_MS(n)=DISABLE andCELL_BAND_TYPE(n)=CELL_BAND_TYPE(0).

If the MS is not in the inner zone of a multiband cell and the MS is in a cell withCELL_BAND_TYPE(0)=PREFERRED_BAND, the cause 14 is checked over all the neighbour cellswith CELL_LAYER_TYPE(n) = lower except the ones with EN_BI-BAND_MS(n)=DISABLE andCELL_BAND_TYPE(n)<>PREFERRED_BAND.

If the MS is not in the inner zone of a multiband cell and the MS is in a cell withCELL_BAND_TYPE(0)<>PREFERRED_BAND, the cause 14 is checked over all the neighbour cellswith CELL_LAYER_TYPE(n) = lower.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

CAUSE = 14 (high level in neighbour lower layer cell for slow mobile) (HO-

21)

AV_RXLEV_NCELL(n) > L_RXLEV_CPT_HO(0,n) n = (1...BTSnum)and MS_SPEED = slowand EN_MCHO_NCELL = ENABLE

### The following equation is checked if and only if CELL_BAND_TYPE is different from theparameter PREFERRED_BAND (This checking is performed at the BSC). It is checked for allneighbour cells n in the preferred band (i.e. CELL_BAND_TYPE(n) = PREFERRED_BAND). If theparameter PREFERRED_BAND is set to ’none’, the equation is never checked.

CAUSE = 21 (high level in neighbour cell in the preferred band) (HO -22)

Traffic_load(0) = MULTIBAND_TRAFFIC_CONDITIONand Traffic_load(n) <> highand AV_RXLEV_NCELL(n) > L_RXLEV_CPT_HO(0,n) + max(0,[MS_TXPWR_MAX(n)-P])and EN_PREFERRED_BAND_HO = ENABLE

- Traffic_load(0) : situation of the traffic in the serving cell.- MULTIBAND_TRAFFIC_CONDITION : Condition on traffic load in the serving cell for a multibandhandover. This parameter can have three different values:

ANY_LOAD: the condition on traffic load is always fulfilled.NOT_LOW: the condition on traffic load is fulfilled only if Traffic_load(0)<>low.HIGH: the condition on traffic load is fulfilled only if Traffic_load(0)=high.

Note : MS_TXPWR_MAX(n) and P are the powers in the preferred band.

• The following cause is checked over all the neighbour cells belonging to the same layer. It meansthat it is checked between cells whose CELL_LAYER_TYPE is single or upper and between cellswhose CELL_LAYER_TYPE is lower.This cause must not be checked between cells which use different frequency band (i.e cells havingdifferent CELL_BAND_TYPE)

If the MS is in the inner zone of a multiband cell, the cause 23 is checked over all the neighbourmultiband cells (FREQUENCY_RANGE=GSM-DCS) which belong to the same BSC as the servingcell.

CAUSE = 23 (Traffic HO) (HO -24)

DELTA_HO_MARGIN(0,n) < 0dBand PBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGIN_INNER +DELTA_HO_MARGIN(0,n)

(n=1...BTSnum)and EN_TRAFFIC_HO(0,n) = ENABLE

DELTA_HO_MARGIN(0,n) is evaluated as for cause 12.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

### If the MS is in the inner zone of a multiband cell, the cause 24 is checked over all theneighbour cells except the ones with EN_BI-BAND_MS(n)=DISABLE and CELL_BAND_TYPE(n) =CELL_BAND_TYPE(0).

If the MS is not in the inner zone of a multiband cell and the MS is in a cell withCELL_BAND_TYPE(0)=PREFERRED_BAND, the cause 24 is checked over all the neighbour cellsexcept the ones with EN_BI-BAND_MS(n)=DISABLE and CELL_BAND_TYPE(n) <>PREFERRED_BAND.

If the MS is not in the inner zone of a multiband cell and the MS is in a cell withCELL_BAND_TYPE(0)<>PREFERRED_BAND, the cause 24 is checked over all the neighbour cells.

CAUSE = 24 (General capture HO) (HO -25)

Traffic_load(0) = CAPTURE_TRAFFIC_CONDITIONand Traffic_load(n) <> highand AV_RXLEV_NCELL(n) > L_RXLEV_CPT_HO(0,n) + max(0,[MS_TXPWR_MAX(n)-P])and EN_GENERAL_CAPTURE_HO = ENABLE

- Traffic_load(0) : situation of the traffic in the serving cell.- CAPTURE_TRAFFIC_CONDITION : Condition on traffic load in the serving cell for a generalcapture handover. This parameter can have three different values:

ANY_LOAD: the condition on traffic load is always fulfilled.NOT_LOW: the condition on traffic load is fulfilled only if Traffic_load(0)<>low.HIGH: the condition on traffic load is fulfilled only if Traffic_load(0)=high.

3.2.2.1.2 Intracell handover causes

3.2.2.1.2.1 Emergency intracell handover causes

The various HO alarms for intracell handover are :

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

In order to take into account the frequency hopping in the RXQUAL evaluation the variableOFFSET_RXQUAL_FH is introduced (for more information refer to [21]).If on the corresponding channel,

Frequency hopping is applied then OFFSET_RXQUAL_FH = Offset_Hopping_HOotherwise OFFSET_RXQUAL_FH = 0

Offset_Hopping_HO is a parameter defined on a per cell basis.

CAUSE = 15 (too high interference level on the uplink)

AV_RXQUAL_UL_HO > L_RXQUAL_UL_H + OFFSET_RXQUAL_FH (HO-8)and AV_RXLEV_UL_HO > RXLEV_UL_IHand EN_INTRA_UL = ENABLEand ( no previous intracell handover for this connection failed

or EN_INTRACELL_REPEATED = ENABLE ).



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel CAUSE = 16 (too high interference level on the downlink)

AV_RXQUAL_DL_HO > L_RXQUAL_DL_H + OFFSET_RXQUAL_FH (HO-9)and AV_RXLEV_DL_HO > RXLEV_DL_IHand EN_INTRA_DL = ENABLEand (no previous intracell handover for this connection failed

A or EN_INTRACELL_REPEATED = ENABLE )

Note : The case where L_RXQUAL_XX_H + OFFSET_RXQUAL_FH > 7 corresponds in the equationsto L_RXQUAL_XX_H + OFFSET_RXQUAL_FH = 7.

The following handover causes are specific to concentric or multiband cell configurations. They arechecked only if CELL_PARTITION_TYPE = CONCENTRIC and the active channel is a TCH.Furthermore, they are only valid for handover from the inner zone to the outer zone of the concentricor multiband cell. Thus, the following conditions are checked only if ZONE_TYPE = INNER_ZONE (itmeans that the channel is in the inner zone partition).

CAUSE = 10 (too low level on the uplink, inner zone)

AV_RXLEV_UL_HO < RXLEV_UL_ZONE (HO-15)and MS_TXPWR = min(P, MS_TXPWR_MAX_INNER)

CAUSE = 11 (too low level on the downlink, inner zone)

AV_RXLEV_DL_HO < RXLEV_DL_ZONE (HO-16)and BS_TXPWR = BS_TXPWR_MAX_INNER

3.2.2.1.2.2 Better zone handover cause

The following handover cause is specific to concentric or multiband cell configurations. It is checkedonly if CELL_PARTITION_TYPE = CONCENTRIC and the active channel is a TCH.Furthermore, it is only valid for handover from the outer zone to the inner zone of the concentric ormultiband cell. Thus, the following condition is checked only if ZONE_TYPE = OUTER_ZONE (itmeans that the channel is in the outer zone partition).

If the FREQUENCY_RANGE = GSM-DCS (the MS is in a multiband cell), the cause is checked onlyif the MS is a multiband one.

The following cause must be checked for all the neighbour cells in the same layer and the samefrequency band as the serving cell.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

CAUSE = 13 (Too high level on the uplink and the downlink, outer zone)

AV_RXLEV_UL_HO > RXLEV_UL_ZONE + ZONE_HO_HYST_UL + (HO-17)(MS_TXPWR - MS_TXPWR_MAX_INNER) + PING_PONG_MARGIN(0, call_ref)

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

and AV_RXLEV_NCELL_BIS(n) ≤ NEIGHBOUR_RXLEV(0,n)and EN_BETTER_ZONE_HO = ENABLE

ZONE_TYPE = OUTER ZONE means that the channel is in the outer zone partition.RXLEV_DL_ZONE : Threshold of downlink received level for interzone handover,RXLEV_UL_ZONE : Threshold of uplink receive level for interzone handover,ZONE_HO_HYST_UL : Hysteresis uplink for interzone handover from the outer to the inner zone

which also takes account of the propagation difference between GSM900 and DCS1800 in thecase of multiband cell,

ZONE_HO_HYST_DL : Hysteresis downlink for interzone handover from the outer to the inner zonewhich also takes account of the propagation difference between GSM900 and DCS1800 and of thedifference of output power in the BTS in the two bands in the case of multiband cell,

MS_TXPWR_MAX_INNER : Maximum permissible transmission power of the mobile station in theinner zone of the concentric or multiband cell,

BS_TXPWR_MAX_INNER : Maximum permissible transmission power of the base station in the innerzone of the concentric or multiband cell,

AV_RXLEV_DL_HO and AV_RXLEV_UL_HO : see previous sections,MS_TXPWR and BS_TXPWR : last BS_POWER and MS_TXPWR_CONF reported by the BTS in

the MEASUREMENT RESULT (see section 4.1).NEIGHBOUR_RXLEV(0,n) : Threshold of maximum downlink received level from the neighbour cells.PING_PONG_MARGIN(0,call_ref) is a penalty put on the cause 13 if :

the immediately precedent zone on which the call has been is the inner zone ofthe serving cell, the last handover was not an external intracell handover (casewhich can occur in the DCS 1800 inner zone of a multiband cell in case ofemergency handover see 3.2.2.3), less than T_HCP seconds have elapsed sincethe last handover.In this case PING_PONG_MARGIN(0,call_ref) = PING_PONG_HCP.If the call was not precedently on the serving cell’s inner zone (case of intercell orintrazone handover), or if the timer T_HCP has expired, thenPING_PONG_MARGIN(0,call_ref) = 0

Note: For the computation of AV_RXLEV_NCELL_BIS(n) refer to [20].

The figure 3.2-2 is the state diagram of the handover detection process (signal level - signal quality)in case of conventional cell environment. The HO causes for microcellular handover are not shown.The threshold values are only indicative.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

Figure 3.2-2 : State diagram for handover detection (signal level - signal quality)

RXLEV

RXQUAL

605040302010

0

0

1

2

3

4

5

6

7

L_RXQUAL_XX_H

L_RXLEV_XX_H L_RXLEV_XX_IH

(HO-8,HO-9)

Levelintercell HO

(HO-2,HO-4)

Quality intercell HO Intracell HO

(HO-1,HO-3)

Power Control



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

The figure 3.2-3 represents the triggering areas of PBGT and traffic handovers according to the trafficload in the serving cell and in the neighbour cell.

HO_MARGIN(n1,n2)

HO_MARGIN(n1,n2) - DELTA_DEC_HO_margin

Traffic_load

PBGT(n2)

Traffic_load(n1)=lowTraffic_load(n2)=high

Traffic_load(n1)=highTraffic_load(n2)=low

Other cases

PBGT Handover

PBGT Handover

Traffic Handover

Traffic Handover

HO_MARGIN(n2,n1) - DELTA_DEC_HO_margin

HO_MARGIN(n2,n1) + DELTA_INC_HO_margin

PBGT Handover PBGT Handover

PBGT(n1)

2*H

O_M

AR

GIN

2*H

O_M

AR

GIN

+DE

LTA

_IN

C_H

O_m

argi

n-D

ELT

A_D

EC

_HO

_mar

gin

2*H

O_M

AR

GIN

+DE

LTA

_IN

C_H

O_m

argi

n-D

ELT

A_D

EC

_HO

_mar

gin

HO_MARGIN(n2,n1)

HO_MARGIN(n1,n2) + DELTA_INC_HO_margin

Handover from n1 to n2

Handover from n2 to n1

Figure 3.2-3: PBGT(n) according to the traffic load in the serving cell and the neighbour cell.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

3.2.2.2 Handover causes priority

The handover causes are checked with the following priority order :

Emergency causes :

- Consecutive bad SACCH frames Cause = 7- Level uplink microcell - high threshold Cause = 17- Level downlink microcell - high threshold Cause = 18- Too low quality Uplink Cause = 2- Too low quality Downlink Cause = 4- Too low level Uplink Cause = 3- Too low level Downlink Cause = 5- Too long MS-BS distance Cause = 6- Too short MS-BS distance Cause = 22- Inner zone too low level Uplink Cause = 10- Inner zone too low level Downlink Cause = 11

- Too high interference intracell Uplink Cause = 15- Too high interference intracell Downlink Cause = 16

Better condition causes :

- high level in neighbour cell in the preferredband

Cause = 21

- high level in neighbour lower layer cell for slow mobile

Cause = 14

- General capture handover Cause = 24- Power budget Cause = 12- Traffic handover Cause = 23- Outer zone level Uplink & Downlink Cause = 13

- Forced Directed Retry Cause = 20- GPRS redirection Cause = 25

Table 3.2-2 : Priority order of alarms for Handover

The better condition causes 21, 14, 24, 12 and 23 have the same priority. For each cell in the list ofpossible candidate cell is associated a cause.If a cell is in the candidate cell list because of 2 different causes, only the one with the highest priorityin the ordered list (cause 21, cause 14, cause 24, cause 12 and cause 23) in which cause 21 has thehighest priority is kept.

3.2.2.3 Indication of raw cell list and preferred layer

After an inter cell handover alarm has been detected, the candidate cell evaluation receives a rawcell list with for each cell one of the handover causes which have been verified and the indication ofthe preferred layer for the target cell.

###Standard cell environment

When the serving CELL_LAYER_TYPE is single, the following rules are applied :



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

The raw cell list is :for Better cell handover (power budget, forced directed retry, traffic handover, general capturehandover and preferred band handover) : the neighbour cells which verify the cause,for Emergency handover : all neighbour cells; and if the MS is in the DCS 1800 inner zone of amultiband cell, the serving cell must be added to the raw cell list with the MS zone indicationOUTER.However, in both cases, if the serving cell is an extended-inner cell, the extended-outer cell mustbe filtered from the raw cell list except in case of handover cause 6.If the serving cell is an extended-outer cell, the extended-inner cell must be filtered from the rawcell list except in case of handover cause 22.

The indication of the preferred layer is PREF_LAYER = upper+single

###Hierarchical cell environment

When the serving CELL_LAYER_TYPE is lower or upper, the following rules are applied :

The cell raw list is calculated as :

- for "better cell" intercell handover causes (causes 12, 14, 20, 21, 23 and 24)

the subset of neighbour cells which verify the handover causes.

If the serving CELL_LAYER_TYPE = lower, there is a cell in the list because of cause 12 andMS_SPEED = fast, the cell raw list must also contain the whole set of internal neighbourumbrella cells with information Traffic_load(n)=low (they do not need to verify the HO cause)

- for emergency handover causes: the whole set of neighbour cells; and if the MS is in the DCS1800 inner zone of a multiband cell, the serving cell must be added to the raw cell list with the MSzone indication OUTER.

Except if the serving CELL_LAYER_TYPE = LOWER, select the whole set of neighbour cellsexcept the umbrella cells n which do not verify:

AV_RXLEV_NCELL(n)>OUTDOOR_UMB_LEV(0,n)and if the MS is in the DCS 1800 inner zone of a multiband cell, the serving cell must be added tothe raw cell list with the MS zone indication OUTER.

The indication of the preferred layer is calculated on basis of two rules

-"Better cell" handover causes (12, 14, 20, 21, 23 and 24) will indicate :

PREF_LAYER = none

Except if the serving CELL_LAYER_TYPE = lower, there is a cell in the list because of cause12 and MS_SPEED = fast. In this case PREF_LAYER = upper.

- the "Emergency" handover causes will indicate :

- When the serving CELL_LAYER_TYPE is lower :

if EN_RESCUE_UM = ENABLE (used generally for microcells) : PREF_LAYER = upperif EN_RESCUE_UM = DISABLE (used for other cell types ) : PREF_LAYER = lowerif EN_RESCUE_UM = INDEFINITE : PREF_LAYER = none

- When the serving CELL_LAYER_TYPE is upper :



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

PREF_LAYER = upper+single

The tables below resume the indications given to the candidate cell evaluation process in hierarchicalenvironment for serving CELL_LAYER_TYPE = lower.

Indication MS_SPEED = fast andthere is a cell in the listbecause of cause 12

MS_SPEED <> fast orHandover cause <> 12

Raw cell listfor Better cell HO

subset of cells verifyingthe HO causes plus all

neighbour umbrellacells with

Traffic_load(n)=low

subset of cells verifyingthe HO cause

PREF_LAYERfor Better cell HO

upper none

table 3.2-3 : indications to candidate evaluation for better cell handover

Indication EN_RESCUE_UM =ENABLE

EN_RESCUE_UM =DISABLE

EN_RESCUE_UM =indefinite

Raw cell listfor Emergency HO

all neighbour cells (1)except if the serving

CELL_LAYER_TYPE =LOWER, exclude

umbrella cells which donot verify

AV_RXLEV_NCELL(n)>OUTDOOR_UMB_LEV(0

,n).

all neighbour cells (1)except if the serving

CELL_LAYER_TYPE =LOWER, exclude

umbrella cells which donot verify

AV_RXLEV_NCELL(n)>OUTDOOR_UMB_LEV(0

,n).

all neighbour cells (1)except if the servingCELL_LAYER_TYPE= LOWER, excludeumbrella cells which

do not verifyAV_RXLEV_NCELL(n)>OUTDOOR_UMB_

LEV(0,n).PREF_LAYER

for Emergency HOupper lower none

table 3.2-4 : indications to candidate evaluation for emergency handover

(1): if the MS is in the DCS 1800 inner zone of a multiband cell, the serving cell must be added to theraw cell list with the MS zone indication OUTER.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

3.2.3 HO Candidate Cell Evaluation

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 evaluationprocess is skipped: the target cell is the serving cell.

The handover detection gives as indication the raw cell list and the preferred layer for the handover.Incase of emergency handover alarms or cause 20 alarm, the cell evaluation will order the cells givenin the raw list, putting in the first position the cells belonging to the preferred layer, having the highestpriority (if EN_PRIORITY_ORDERING=ENABLE) and/or having the same frequency band type as theserving cell. In case of an intercell handover alarm, if the serving cell belongs to the raw cell list(emergency handover from the DCS 1800 inner zone of a multiband cell), this cell is put at the end ofthe 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 cellsgiven in the raw list, putting in the first position the cells belonging to the preferred layer and havingthe highest priority (if EN_PRIORITY_ORDERING=ENABLE).

Input parametersThis process receives (refer to input flows described in section 2.3.6) :

- measurements of up to 32 neighbour cells (TCU internal indication) handled by the BSC cellbook-keeping function.- the raw cell list of potential candidates to be ordered with for each of them one of the handovercauses which have been verified.- the preferred layer for the target cell indicated by the variable PREF_LAYER- the cell configuration parameters which contains the variable CELL_BAND_TYPE.

Determination of the target cell list

In case of emergency handover alarm or cause 20 alarm, the target cell list is built from the cellordering according to target layer, target band (see 2.3.4.2) and the priority of each cells (ifEN_PRIORITY_ORDERING=ENABLE) and from the cell evaluation function indicated by the flagCELL_EV associated to the serving cell (see 3.2.3.1 and 3.2.3.2).The priority of each cells is defined by the parameter PRIORITY(0,n).

The ordering of the target cell list (from the higher priority to the lower one) is performed according tothe following scheme :

{Candidate cells whose CELL_LAYER_TYPE = PREF_LAYER{

Candidate cells which have the lowest PRIORITY(0,n){

Candidate cells whose CELL_BAND_TYPE = serving CELL_BAND_TYPE{

cell ordering according to cell evaluation function}Candidate cells whose CELL_BAND_TYPE <> serving CELL_BAND_TYPE{

cell ordering according to cell evaluation function}

}Candidate cells which have the next lowest PRIORITY(0,n){




All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel



}...

}Candidate cells whose CELL_LAYER_TYPE <> PREF_LAYER{





}Candidate cells which have the next lowest PRIORITY(0,n){




}...

}Serving cell (MS zone indication = OUTER)}

In case of better condition handover alarm except cause 20, the target cell list is built from the cellordering according to target layer and the priority of each cells (ifEN_PRIORITY_ORDERING=ENABLE) and from the cell evaluation function indicated by the flagCELL_EV associated to the serving cell (see 3.2.3.1 and 3.2.3.2).The priority of each cells is defined by the parameter PRIORITY(0,n).

The ordering of the target cell list (from the higher priority to the lower one) is performed according tothe following scheme :

Candidate cells whose CELL_LAYER_TYPE = PREF_LAYER{





All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

Candidate cells which have the next lowest PRIORITY(0,n){


.

.

.}Candidate cells whose CELL_LAYER_TYPE <> PREF_LAYER{


cell ordering according to cell evaluation function}Candidate cells which have the next lowest PRIORITY(0,n){


.

.

.}

Note : - if PREF_LAYER = none, only the second part of the scheme (i.e. candidate cells whoseCELL_LAYER_TYPE <> PREF_LAYER) is considered.

- if PREF_LAYER = upper+single, the condition for the first part of the scheme will be :CELL_LAYER_TYPE = upper or CELL_LAYER_TYPE = single. The condition for thesecond part will be CELL_LAYER_TYPE <> upper and CELL_LAYER_TYPE <> single.

- if EN_PRIORITY_ORDERING=DISABLE, the priority(0,n) is not taken into account.

The flag CELL_EV is managed by the network operator on a per cell basis. It has two values, whichcorrespond to the two cell evaluation functions ORDER and GRADE (see 3.2.3.1 and 3.2.3.2 ) .A filtering process can be applied to the target list before the ORDER or GRADE evaluation processin case of emergency handovers. The filtering process, the ORDER or GRADE evaluation processare not applied to the serving cell when it is in the target cell list. The serving cell is always at the endof the target cell list.After the cell evaluation processing, the list of candidate target cells with their cause is provided to thefunction in charge of the handover decision and execution.

Output parametersThe Handover candidate cell evaluation function shall provide the BSC entities in charge of HOexecution and channel allocation the following parameters :- list of candidate cells with their cause and with the serving cell at the end of the list in case ofemergency handover from the DCS 1800 inner zone of a multiband cell.

The HO causes together with the CELL_PARTITION_TYPE parameter shall be used by the BSCchannel allocation entity (for further details, see [16]) as described in the next table :



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

CELL_PARTITION_TYPE ###

HO cause ###

Normal Concentric

15, 16Intracell handoverSelect a channel in thesame cell

Intrazone or interzonehandoverSelect a channel in thesame cell

10, 11, 13Not applicable Interzone handover

Select a channel in theother zone

OthersIntercell handoverChannel allocation isdescribed in ref [16].

Intercell handoverChannel allocation isdescribed in ref [16].

Table 3.2-5 : Channel allocation strategy

3.2.3.1 Filtering process

The filtering process allows to filter out cells from the target list before the ORDER or GRADEevaluation process.This process can be enabled or disabled by the flag EN_PBGT_FILTERING.This filtering process is inhibited for better cell handovers (HO causes 12, 14, 20, 21, 23 or 243). It isnot applied to the serving cell when it is in the target cell list.

If EN_PBGT_FILTERING is set to enable, all the cells(n) which do not fulfil the following condition(HO-13) are rejected from the cell list sent to the ORDER or GRADE evaluation process.

PBGT(n) > HO_MARGIN_XX(0,n) + OFFSET_HO_MARGIN_INNER (HO-13)

OFFSET_HO_MARGIN_INNER is only applied when the MS is in the inner zone of a concentric ormultiband cell.

HO_MARGIN_XX(0,n) has the following values:HO_MARGIN_XX(0,n)=HO_MARGIN_QUAL(0,n) If cause =2, 4 or 7HO_MARGIN_XX(0,n)=HO_MARGIN_LEV(0,n) If cause =3, 5, 17 or 18HO_MARGIN_XX(0,n)=HO_MARGIN_DIST(0,n) If cause =6 or 22

If no cell fulfils the condition and the serving cell does not belong to the target cell list, the target celllist is empty and no further action is carried out.If the target list is not empty, it is sent to the ORDER or GRADE evaluation process according toCELL_EV.

3.2.3.2 ORDER cell evaluation process

Note that the word "PATHLOSS" was in the past sometimes used instead of "ORDER".

The value of ORDER(n) for each neighbour cell(n) is computed according to the following formula :

if EN_LOAD_ORDER = ENABLE and cell n is internal to the BSC



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

ORDER(n) = PBGT(n) + LINKfactor(0,n) (HO-10)+ FREEfactor(n) - FREEfactor(0)- HO_MARGIN_XX(0,n)

if EN_LOAD_ORDER = DISABLE or cell n is external to the BSC

ORDER(n) = PBGT(n) + LINKfactor(0,n) - HO_MARGIN_XX(0,n) (HO-10)

For emergency handover causes, HO_MARGIN_XX(0,n) has the following values:HO_MARGIN_XX(0,n)=HO_MARGIN_QUAL(0,n) If cause =2, 4 or 7HO_MARGIN_XX(0,n)=HO_MARGIN_LEV(0,n) If cause =3, 5, 17 or 18HO_MARGIN_XX(0,n)=HO_MARGIN_DIST(0,n) If cause =6 or 22

For better cell handover causes, HO_MARGIN_XX(0,n)=HO_MARGIN(0,n)

- The flag EN_LOAD_ORDER is settable by OMC command.- LINKfactor(0,n), HO_MARGIN_QUAL(0,n), HO_MARGIN_LEV(0,n), HO_MARGIN_DIST(0,n) and

HO_MARGIN(0,n) are parameters set by OMC command for each neighbour cell(n).- FREEfactor(n) : weighting factor that takes into account the number of free traffic channels in a cell.

- For TCH, FREEfactor(n) is set to the value according to table T2,- for SDCCH : FREEfactor(n) = 0.

- PBGT(n) is the power budget between the serving cell(0) and cell(n). For the formula, see appendixA.All neighbour cells(n) which fulfil the following condition (HO-11) are sorted according to theirORDER(n) :

AV_RXLEV_NCELL(n) > RXLEVmin(n) + max(0,[MS_TXPWR_MAX(n)-P]) (HO-11)

For multiband handover, P considered in (HO-11) corresponds to the classmark power in thefrequency band used by the cell n.

Equation (HO-11) ensures that the MS can communicate in the cell n.

For any handover cause, the first cell in the list is taken as target cell, i.e. the cell with the highestvalue of ORDER(n). The cells do not need to fulfil any other condition.

If no cell fulfils the condition and the serving cell does not belong to the target cell list, the target celllist is empty and no further action is carried out.

3.2.3.3 GRADE cell evaluation process

The value of GRADE(n) for each neighbour cell(n) is computed according to the following formula :

if EN_LOAD_ORDER = ENABLE and cell n is internal to the BSC

GRADE(n) = PBGT(n) + LINKfactor(0,n) (HO-12)+ LOADfactor(n)

if EN_LOAD_ORDER = DISABLE or cell n is external to the BSC

GRADE(n) = PBGT(n) + LINKfactor(0,n) (HO-12)



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

- The flag EN_LOAD_ORDER is settable by OMC command.- LINKfactor(0,n) is a parameter set by OMC command for each cell(n).

LINKfactor (n1,n2) allows the operator to handicap or to favour the cell n1 with respect to itsneighbour cell n2. In particular, it can be used to disadvantage an external cell when an internal cellis also a possible candidate.

- LOADfactor(n) : weighting factor that takes into account the relative load of traffic channels in a cell. For TCH: LOADfactor(n) is set according to the table T1,

For SDCCH : LOADfactor(i) = 0.

The real time traffic load and corresponding FREEfactor and LOADfactor are only known for thecells that are controlled by the current BSC. For the cells controlled by another BSC the traffic loaddoes not influence the candidate evaluation.

- PBGT(n) is the power budget between the serving cell(0) and the cell(n) (see appendix A fordefinition).

The greater is GRADE(n), the most suitable is the neighbour cell n compared to the serving cell.

All neighbour cells(n) which fulfil the following condition are sorted according to their GRADE(n).

Equation (HO-11) ensures that the MS can communicate in the cell n.

AV_RXLEV_NCELL(n) > RXLEVmin(n) + max(0,[MS_TXPWR_MAX(n)-P]) (HO-11)

For multiband handover, P considered in (HO-11) corresponds to the classmark power in thefrequency band used by the cell n.

For any handover cause the first cell in the list is taken as target cell, i.e. the cell with the highestvalue of GRADE(n). If no cell fulfils the condition and the serving cell does not belong to the targetcell list, the target cell list is empty and no further action is carried out.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

3.2.3.4 Calculation of LOADfactor, FREEfactor

The following tables T1 and T2 define the sets of parameters used for the cell evaluation processes :

Table T1 : LOADfactor

l = [1 - (free TCH/total TCH)] * 100%.

l in cell(n) LOADfactor(n)

### LOADlevel_1 LOADfactor_1

LOADlevel_1 ### ### LOADlevel_2 LOADfactor_2



LOADlevel_4 ### LOADfactor_5

Table T2 : FREEfactor

t = absolute number of free TCH

t in cell(n) FREEfactor(n)

### FREElevel_1 FREEfactor_1

FREElevel_1 ### ### FREElevel_2 FREEfactor_2



FREElevel_4 ### FREEfactor_5

LOADfactor(n) and FREEfactor(n) are received in the message “TCH usage information” everyTCH_INFO_PERIOD seconds from the Resource updating function (ref to [16]).

Note : The count of free and total TCH for the calculation of l and t is based on timeslots and not onchannels. So, this count does not take into account the free half rate channels in case of dual ratecapability. It means that a TCH timeslot is considered as non-free as soon as a HR channel isallocated on this timeslot.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

3.2.4 Handover alarm management

Each time a candidate cell list is provided by the handover candidate cell evaluation function or bythe candidate cell evaluation function for forced directed retry and T_FILTER is not running, ahandover alarm containing the candidate list is sent to the BSC function in charge of the handoverexecution and T_FILTER is started.

Each time a candidate cell list is provided by the handover candidate cell evaluation function or bythe candidate cell evaluation function for forced directed retry and T_FILTER is running, T_FILTER isrestarted and the new list is compared to the previous candidate cell list.

If the list has changed (ie one or more cells have disappeared in relation to the previous list and/orone or more cells are new in the list), a handover alarm containing the candidate list is sent to theBSC function in charge of the handover execution.If the new list has not changed (ie the cells are the same, the number of cells is the same but theorder in the list can be different), no handover alarm is sent to the handover management entity.

New candidate cell listfrom the candidate cell evaluation function

IsT_FILTERrunning?

YES NO

Start T_FILTER.A handover alarm containing the candidate cell list is sent to the handover management entity

Is thecandidate cell

list different fromthe previous

one?

YES NO

Restart T_FILTER.A handover alarm containing the candidate cell list is sent to the handover management entity

Restart T_FILTER

Figure 3.2-4: Handover alarm management algorithm.

If the timer T_FILTER expires, a handover alarm message containing no candidate cell is sent to thehandover management entity. This message means: “no more alarm”.The expiry of T_FILTER means that the handover alarm initially triggered is considered as no longervalid.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

3.3 Directed retry preparation

3.3.1 General

3.3.1.1 Directed retry preparation enabling and disabling

Enabling

The directed retry preparation is enabled upon reception of an indication from the handovermanagement entity (BSC internal message, see [14]). This indication is called "Enable directed retry"in the SADT diagram of section 2.3.6.The directed retry is supported by the same processes as the handover preparation except for forceddirected retry (see section 2.4), consequently :- for directed retry on handover alarms, the enabling consists in changing the behaviour of the

candidate cell evaluation process (see section 3.2.3). This process looks for target cells for TCHchannel instead of SDCCH channel.

- for forced directed retry : both the detection and candidate cell evaluation processes are enabled atthis point in time.

Note : The handover preparation function is enabled when the SDCCH connection is established(reception of the ESTABLISH INDICATION from the corresponding BTS). Therefore the handoverpreparation is always enabled before the directed retry preparation. This allows the detectionprocess for forced directed retry, after its enabling, to get immediately measurements from theneighbouring cell measurements book-keeping.

When the directed retry preparation is enabled, SDCCH_COUNTER is stopped and not restarted.

Disabling

The directed retry preparation is disabled whenever the BSC initiates a channel release on the radiointerface.

3.3.1.2 Directed retry preparation function

The directed retry preparation function is completely handled by the BSC. The input parameters ofthis function are provided by the active channel preprocessing function (refer to [20]) which handlesthe neighbour cell list book-keeping. As the handover preparation function, the directed retrypreparation function can be divided into two processes : Alarm detection and Candidate cellevaluation.

Once the directed retry preparation enabled, a directed retry on handover alarms or forced directedretry alarm can be detected every SACCH multiframe upon reception of the averaged measurementsfor directed retry detection.

Once a directed retry alarm is detected, the alarm detection process sends to the candidate cellevaluation process the list of MS neighbouring cells with for each of them one of the handover causeswhich have been verified.

The candidate cell evaluation builds a cells list which is according to the case and the value ofT_FILTER sent or not to the BSC function in charge of the handover management entity (see 3.2.4.).

3.3.2 Alarm Detection

Directed retry on handover alarms



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

The detection process is the Handover detection process described in section 3.2.2. except thatinterzone handover alarms (causes = 10, 11, 13) and intracell handover alarms (causes = 15, 16)must be ignored.Only intercell handover alarms are taken into account i.e. all handover causes except causesmentioned above.

Forced directed retry

The following condition is checked every measurement reporting period and if at least one inputpreprocessed parameter AV_RXLEV_NCELL_DR(n) is available.

CAUSE = 20 (high level in neighbour cell for forced directed retry)

AV_RXLEV_NCELL_DR(n) > L_RXLEV_NCELL_DR(n) ( n = 1 ... BTSnum ) (DR -1)and EN_FORCED_DR = ENABLE

The threshold L_RXLEV_NCELL_DR(n) is the observed level from the neighbour cell n at the borderof the area where forced directed retry is enabled (see 2.4.1). This threshold fixes the size of theoverlapping area where forced directed retry can be performed. It should be greater thanRXLEVmin(n).

Alarms priority

As explained in section 2.4, the handover alarms have priority over the forced directed retry alarm(HO cause 20). The priority order for handover alarms is indicated in section 3.2.2.2.

3.3.3 Candidate cell evaluation

Directed retry on handover alarmsThe candidate cell evaluation process is the one described in section 3.2.3 for TCH channel.

Forced directed retryThe candidate cell evaluation is performed when an alarm for forced directed retry is raised (cause =20).

This candidate cell evaluation process is performed as specified in Section 3.2.3. except that the cellevaluation function is reduced to a specific power budget evaluation called PBGT_DR(n).

All neighbour cells n which meet the following condition (DR-3) and (DR-4) are sorted according to thepriority scheme described in Section 3.2.3. and according to their PBGT_DR(n) :

PBGT_DR(n) = AV_RXLEV_NCELL_DR(n) - AV_RXLEV_PBGT_DR (DR-2)- (BS_TXPWR_MAX - AV_BS_TXPWR_DR)- (MS_TXPWR_MAX(n) - MS_TXPWR_MAX)

For further details on the PBGT formula, see section 3.2.2.1.1.3 and appendix A.

AV_RXLEV_NCELL_DR(n) > RXLEVmin(n) + max(0,[MS_TXPWR_MAX(n)-P]) (DR-3)



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

t(n) > FREElevel_DR(n) (DR-4)

with :- FREElevel_DR(n) : minimum threshold of free TCHs in the neighbour cell n for forced directed retry.- t(n) : absolute number of free TCHs in the neighbour cell n.

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

Note : if the BTS has dual rate capability, t(n) = absolute number of free Dual Rate TCH

L_RXLEV_NCELL_DR(n) and FREElevel_DR(n) are parameters set by O&M for each neighbour celln.

If no cell fulfils the condition, the target cell list is empty and no further action is carried out.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

3.4 GPRS redirection preparation

3.4.1 General

3.4.1.1 GPRS redirection preparation enabling

Enabling

The GPRS redirection preparation is enabled upon reception of an indication from the radio and linkestablishment entity (BSC internal message, see [6]). This indication is called "Enable GPRSredirection" in the SADT diagram of section 2.3.6. The detection and candidate cell evaluationprocesses are enabled at this point in time.

Note : SDCCH handovers and SDCCH_COUNTER are disabled in case of GPRS redirection.

Disabling

The GPRS redirection preparation is disabled whenever the BSC initiates a channel release on theradio interface.

3.4.1.2 GPRS redirection preparation function

The GPRS redirection preparation function is completely handled by the BSC. The input parametersof this function are provided by the active channel preprocessing function (refer to [20]) which handlesthe neighbour cell list book-keeping. As the handover preparation function, the GPRS redirectionpreparation function can be divided into two processes : Alarm detection and Candidate cellevaluation.

Once the GPRS redirection preparation enabled, a GPRS redirection can be detected every SACCHmultiframe upon reception of the averaged measurements.

Once a GPRS redirection alarm is detected, the alarm detection process sends to the candidate cellevaluation process the list of MS neighbouring cells.

The candidate cell evaluation builds a cells list which is according to the case and the value ofT_FILTER sent or not to the BSC function in charge of the handover management entity (see 3.2.4.).

3.4.2 Alarm Detection

The following condition is checked over all the neighbour cells for which EN_GPRS(n) = TRUE everymeasurement reporting period.

CAUSE = 25 (high level in neighbour cell for GPRS redirection)

AV_RXLEV_NCELL_DR(n) > L_RXLEV_NCELL_DR(n) ( n = 1 ... BTSnum ) (DR -1)

The threshold L_RXLEV_NCELL_DR(n) is the minimum level necessary for a GPRS transfer. Itshould be greater than RXLEVmin(n).



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

L_RXLEV_NCELL_DR(n) is a parameter set by O&M for each neighbour cell n.

3.4.3 Candidate cell evaluation

The candidate cell evaluation is performed when an alarm for GPRS redirection is raised (cause =25).

This candidate cell evaluation process is performed as specified in Section 3.2.3. except that the cellevaluation function is reduced to a specific power budget evaluation called PBGT_DR(n).

All neighbour cells n which meet the following condition (DR-3) are sorted according to the priorityscheme described in Section 3.2.3. and according to their PBGT_DR(n) :

PBGT_DR(n) = AV_RXLEV_NCELL_DR(n) - AV_RXLEV_PBGT_DR (DR-2)- (BS_TXPWR_MAX - AV_BS_TXPWR_DR)- (MS_TXPWR_MAX(n) - MS_TXPWR_MAX)

For further details on the PBGT formula, see section 3.2.2.1.1.3 and appendix A.

AV_RXLEV_NCELL_DR(n) > RXLEVmin(n) + max(0,[MS_TXPWR_MAX(n)-P]) (DR-3)

If no cell fulfils the condition, the target cell list is empty and no further action is carried out.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

4. INTERFACES DESCRIPTION

4.1 GSM interfaces/Physical interfaces

The messages used by the handover algorithms are carried on the Abis interface only.Note that for handover decision and execution, all the relevant messages transmitted on the Air, Abis,A interfaces are described in [9] and [10].

Note : In ref [20] is given the general structure of the Abis messages required by the handoveralgorithm. In particular, the fields for which it is stated in the GSM Technical Specification 08.58 ([3])"the coding of this field requires further elaboration" are described. For the coding of the othersinformation elements, refer to [3].

4.2 Internal interfaces

The information exchanged between handover functions is described in sections 2 and 4.4.

4.3 Timers list

NAME RANGE BIN.RANGE BITS

T_FILTER (0 to 31)x960 ms 0:31 8

Time after which a “no alarm” message (analarm message with no candidate cell, seesection 3.3.) is sent to the handovermanagement entity, if no new alarm has beendetected whilst running.

0=0 ms

31=31x960ms

T_HCP (0 to 240 ) sec 0:240 8

Time during which a handicap of PING_PONG_HCPis applied to the preceding cell power budget

0=0 s 240 = 240s

LOAD_EV_PERIOD 1 to 30 1:30 8

Number of load samples (received everyTCH_INFO_PERIOD) for load averaging

1=1 , 30 = 30

TCH_INFO_PERIOD 2 to 25.5 sec 20:255 8

periodicity of the sending of the message 'TCHusage information' to the TCUs.

20=2 s, 255 =25.5 s

4.4 Parameters and variables list

This section provides a list of all the variables and parameters used in the algorithms and thusencountered in the text. For each entry will be found :- its name,- its meaning,- its physical range,



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

- its binary range,- the number of bits into which it is encoded.The variables and parameters are ranked in the alphabetical order.

4.4.1 Handover

NAME RANGE BIN. RANGE BITS

AV_BS_TXPWR_DR max -30 to min 0 dB 0:30 5

Average Transmit Power at BS for PBGT_DRevaluation

step size 1 dB (relativevalue)

0 = 0 dB30 = -30 dB

AV_BS_TXPWR_HO max -30 to min 0 dB 0:30 5

Average Transmit Power at BS for PBGT evaluation step size 1 dB (relativevalue)

0 = 0 dB30 = -30 dB

AV_LOAD(n) 0 to 100 % 0:100 8

Averaging load of the cell n step size 1%

with a period equal to LOAD_EV_PERIOD

AV_RXLEV_DL_HO -110 to -47 dBm 0:63 8

Average Receive Downlink Level step size 1 dBm 0=-110

of serving cell (used for Handover) 63=-47

AV_RXLEV_DL_MCHO -110 to -47 dBm 0:63 8

Average Receive Downlink Level of serving step size 1 dBm 0=-110

cell (used for Microcellular Handover) 63=-47

AV_RXLEV_NCELL(n) -110 to -47 dBm 0:63 8

Average Receive Level step size 1 dBm 0=-110

neighbour cell n at MS 63=-47

AV_RXLEV_NCELL_BIS(n) -110 to -47 dBm 0:63 8

Average Receive Level step size 1 dBm 0=-110

neighbour cell n at MS used for cause 13 63=-47

AV_RXLEV_UL_HO -110 to -47 dBm 0:63 8

Average Receive Uplink Level step size 1 dBm 0=-110

of serving cell (used for Handover) 63=-47

AV_RXLEV_UL_MCHO -110 to -47 dBm 0:63 8

Average Receive Uplink Level of serving step size 1 dBm 0=-110

cell (used for Microcellular Handover) 63=-47

AV_RXLEV_PBGT_HO -110 to -47 dBm 0:63 8

Average Receive Downlink Level of step size 1 dBm 0=-110

serving cell (PBGT calculation) 63=-47

AV_RXQUAL_UL_HO 0 to 7 0:7 coded with a 8

Average Receive Uplink Quality of stepsize 0.1 step size of 0.1

serving cell (used for Handover)



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

AV_RXQUAL_DL_HO 0 to 7 0:7 coded with a 8

Average Receive Downlink Quality of stepsize 0.1 step size of 0.1

serving cell (used for Handover)

AV_RANGE_HO 0 to 63 x 3.69µs 0:63 8

Average Distance between MS and BS

BCCH_FREQ 0 to 1023 0:1023 16

BCCH frequency used in the serving cell.

BCCH_FREQ(n) 0 to 1023 0:1023 16

BCCH frequency used in the neighbour cell n.

SACCH_BFI 0 or 1 0:1 1

Bad Frame Indicator 0 : good frame

of the SACCH frame 1 : bad frame

BS_TXPWR max -30 to min 0 dB 0:15 5

Transmit Power at BS step size 2 dB (relativevalue)

0 = 0 dB15 = -30 dB

BS_TXPWR_MAX max -30 to min 0 dB 0:15 8

Maximum Transmit Power at BS step size 2 dB 0 = 0 dB

(relative value) 15= -30 dB

BS_TXPWR_MAX_INNER max - 30 to min 0 dB 0:15 8

Maximum BS Transmit Power permissible in the step size 2 dB 0 = 0 dB

inner zone of the concentric or multiband cell. (relative value) 15= -30 dB

BS_TXPWR_MIN max - 30 to min 0 dB 0:15 8

Minimum Transmit Power at BS step size 2 dB 0 = 0 dB

(relative value) 15= -30 dB

BSIC(n) 0 to 63 0:63 8

Base Station Identity Code of cell n

BTSnum 0 to 32 0:32 8

Number of neighbouring cells for whichmeasurements made by the MS are available

CAPTURE_TRAFFIC_CONDITION ANY_LOAD, NOT_LOW,HIGH

0 : 2 8

Condition on traffic load in the serving cell for ageneral capture handover

0 : ANY_LOAD1 : NOT_LOW2 : HIGH

C_DWELLcounter for time during which the MS has been insidethe serving lower layer cell

0 : 255 SACCH framesstepsize 1

0 : 255 0



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

C_DWELL(n)counter for time during which the MS has beenreporting the neighbour lower layer cell when on theupper layer with a minimum receive level ofL_RXLEV_CPT_HO(0,n)

0 : 255 SACCH framesstepsize 1

0 : 255 0

CELL_BAND_TYPE GSM or DCS 1 : GSM 2

Indicator of the BTS frequency band type 2 : DCS

CELL_DIMENSION_TYPE Macro or Micro 0 : Macro 2

Indicator of BTS dimension type 1 : Micro

CELL_EV ORDER or GRADE 0 : ORDER 1

Indicator of which cell evaluation process is chosen 1 : GRADE

CELL_LAYER_TYPEIndicator of BTS layer type

Single, or Upper, orLower

0 : Single1 :Upper

2

2 : Lower

CELL_PARTITION_TYPE Normal or Concentric 0 : Normal 2

Indicator of cell partition type (frequency use) 1 : Concentric

CELL_RANGE Normal, Extended inneror Extended outer

0 : Normal1 : Extended outer

2

Indicator of extended cell feature 2 : Extended inner

DELTA_DEC_HO_margin 0 to 24 dB 0:24 8

allows the cause 23 detection when the traffic inthe serving cell is high and is low in the cell n

stepsize 1 dB

DELTA_HO_MARGIN(0,n) 0 0 8

-DELTA_DEC_HO_marginDELTA_INC_HO_margin

-DELTA_DEC_HO_marginDELTA_INC_HO_margin

DELTA_INC_HO_margin 0 to 24 dB 0:24 8

penalises the cause 12 detection when thetraffic in the serving cell is low and is high in thecell n

stepsize 1 dB

DWELL_TIME_STEP 0 :30 s 0:0 8

increment or decrement value of MIN_DWELL_TIME stepsize 1s 30 : 30

for traffic load control in the umbrella cells

EN_BETTER_ZONE_HO enable or disable 0 : disable 1

Enable/disable flag for HO cause 13 1 : enable

EN_BI-BAND_MS(n) enable or disable 0 : disable 1

Enables/disables the incoming handovers of bi-bandMSs from the preferred-band into a classical bandcell

1 : enable



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

EN_DIST_HO enable or disable 0 : disable 1


EN_GENERAL_CAPTURE_HO enable or disable 0 : disable 1


EN_GPRS(n) enable or disable 0 : disable 1

Enable/disable GPRS for cell n 1 : enable

EN_GPRS_DIRECTION enable or disable 0 : disable 1

Enable/disable GPRS redirection 1 : enable

EN_INTRACELL_REPEATED enable or disable 0 : disable 1

Enable/disable flag for repetition of intracell HO 1 : enable

EN_INTRA_DL enable or disable 0 : disable 1


EN_INTRA_UL enable or disable 0 : disable 1


EN_LOAD_ORDER enable or disable 0 : disable 1

Enable/disable influence of traffic load in thecandidate cell ranking process

1 : enable

EN_MCHO_NCELL enable or disable 0 : disable 1


EN_MCHO_H_DL enable or disable 0 : disable 1


EN_MCHO_H_UL enable or disable 0 : disable 1


EN_MCHO_RESCUE enable or disable 0 : disable 1


EN_PREFERRED_BAND_HO enable or disable 0 : disable 1


EN_PBGT_HO enable or disable 0 : disable 1


EN_PBGT_FILTERING enable or disable 0 : disable 1

Enable/disable flag for filtering process 1 : enable

EN_PRIORITY_ORDERING enable or disable 0 : disable 1

Enables/disables the use of the parameterPRIORITY(0,n) in the candidate cell evaluationprocess

1 : enable



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

EN_RESCUE_UM enable, disable orindefinite

0 : disable 2

Enable/disable to direct emergency handoverstowards umbrellas preferentially

1 : enable2 : indefinite

EN_RXLEV_DL enable or disable 0 : disable 1


EN_RXLEV_UL enable or disable 0 : disable 1


EN_RXQUAL_DL enable or disable 0 : disable 1


EN_RXQUAL_UL enable or disable 0 : disable 1


EN_SPEED_DISC enable or disable 0 : disable 1

Enable/disable flag for speed discrimination onmobiles in the lower layer cells

1 : enable

EN_TRAFFIC_HO(0,n) enable or disable 0 : disable 1

Enable/disable flag for HO cause 23 from the servingcell and the cell n

1 : enable

FREEfactor_k -16 to 16 dB -16:16 8

5 correction factors of ORDER depending on freelevel of cell (n) expressed in number of free TCH(Table T2).

step size 1 dB

FREElevel_k 0 to 255 channels 0:255 8

4 boundaries for free TCH channel classification(Table T2)

step size : 1 channel

FREQ(n) 0 to 31 0:31 8

Index of the BCCH frequency used by cell n. Samecoding rule as in MEASUREMENT REPORTmessage. This index is relative to the BA allocation ,see [1].

FREQUENCY_RANGEIndicates in which frequency range the cell operates.

GSM900, DCS1800, E-GSM, DCS1900, GSM-DCS

0:40 : GSM9001 : DCS1800

8

2 : E-GSM3 : DCS19004 : GSM-DCS

GRADE(n) -179 to 149 dB -179:+149 16

Grade Evaluation of cell n used for ranking

H_LOAD_OBJ 0 to 100% 0 : 10 8

Maximum desired load on umbrella cell step size 10 % 0 = 0 %



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

defined for each umbrella cell 10 = 100%

H_MIN_DWELL_TIME 0 to 120 s 0 : 0 s 1

maximum value for MIN_DWELL_TIME step size 1 s 120 : 120 s

HOCause ValueHandover Cause

0, 2, 3, 4, 5, 6, 7, 10,11, 12, 13, 14, 15, 16,17, 18, 20, 21, 22, 23

0:230=0.. 23=23

8

HO_INTERCELL_ALLOWED enable or disable 0 : disable 1

Enable/disable flag for HO intercell 1 : enable

HO_MARGIN(n1,n2) -127 to +127 dB -127 :+127 8

Basic Margin for Handover between cell n1 and n2 step size 1 dB

HO_MARGIN_DIST(n1,n2) -127 to +127 dB -127 :+127 8

Basic Margin for Handover (distance causes)between cell n1 and n2

step size 1 dB

HO_MARGIN_LEV(n1,n2) -127 to +127 dB -127 :+127 8

Basic Margin for Handover (level causes) betweencell n1 and n2

step size 1 dB

HO_MARGIN_QUAL(n1,n2) -127 to +127 dB -127 :+127 8

Basic Margin for Handover (quality causes) betweencell n1 and n2

step size 1 dB

L_LOAD_OBJ 0 to 100% 0 : 10 8

Minimum desired load on umbrella cells step size 10 % 0 = 0 %

defined for each umbrella cell 10 = 100%

L_MIN_DWELL_TIME 0 to 120 s 0 : 0 s 1

minimum value for MIN_DWELL_TIME step size 1 s 120 : 120s

L_RXLEV_DL_H -110 to -47 dBm 0:63 8

Minimum Receive Level step size 1 dBm 0=-110 dBm

for Downlink Level Handover 63=-47 dBm

L_RXLEV_CPT_HO(0,n) -110 to -47 dBm 0:63 8

Minimum Receive Level on Downlink for handover step size 1 dBm 0=-110 dBm

from umbrella to neighbour lower layer cell n or from classical band cell to preferred band cell n

63=-47 dBm

L_RXLEV_UL_H -110 to -47 dBm 0:63 8


for Uplink (Handover) 63=-47 dBm

L_RXQUAL_DL_H 0 to 7 0:7 coded with a 8

Minimum Receive Quality stepsize 0.1 stepsize of 0.1

on Downlink (Handover)

L_RXQUAL_UL_H 0 to 7 0:7 coded with a 8



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

Minimum Receive Quality stepsize 0.1 stepsize of 0.1

on Uplink (Handover)

L_TIME_ADVANCE 0 to 63 x 3.69µs 0:63 8

Minimum Distance for Handover from the extendedouter zone of a cell

LINKfactor(n1,n2) -24 to +24 dB -24:24 8

static handicap for handover evaluation between celln1 and n2

step size 1 dB

LOADfactor_k -16 to 0 dB -16:0 8

5 correction factors of GRADE depending on load ofcell(n) expressed in percentage of TCH load (Table T1)

LOADlevel_k 0 to 100 (% of free TCH) 0:100 8

4 boundaries for TCH cell load classification (Table T1)

MIN_CONNECT_TIME 0 to 120 s 0 : 0 s 8

time in a lower layer cell to separate slow and fastMS

step size 1 s 120 : 120 s

MIN_DWELL_TIME 0 to 120 s 0 : 0 s 8

time reporting a neighbour lower layer cell in anumbrella cell to trigger a handover to the lower layer

step size 1 s 120 : 120 s

MS_SPEEDEstimation for mobile speed discrimination process indefinite, slow, fast

0 :2,0 : indefinite1 : slow2 : fast

2

MS_TXPWRTransmit Power at MS

See [18] See [18] 5

MS_TXPWR_CONF See [18] See [18] 8

Confirmation of new Transmit Power to BS

MS_TXPWR_MAXMaximum Transmit Power at MS

See [18] See [18] 8

MS_TXPWR_MAX(n)Maximum Transmit Power from MS allowed by cell n

See [18] See [18] 8

MS_TXPWR_MAX_INNERMaximum MS transmit power permissible in the innerzone of the concentric or multiband cell.

See [18] See [18] 8

MS_TXPWR_MINMinimum Transmit Power at MS

See [18] See [18] 8

MULTIBAND_TRAFFIC_CONDITION ANY_LOAD, NOT_LOW,HIGH

0 : 2 8

Condition on traffic load in the serving cell for amultiband handover

0 : ANY_LOAD1 : NOT_LOW2 : HIGH



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

N_BAD_SACCH 1 to 128 1:128 8

Threshold of consecutive bad SACCH frames 1=1 SACCHframes128=128 SACCHframes

NBR_ADJ 0 to 64 cells 0:64 8

Number of adjacent 0=0

cells for this BTS 64=64

NEIGHBOUR_RXLEV(0,n) -110 to -47 dBm 0:63 8

Threshold of maximum downlink received level from step size 1 dBm 0=-110 dBm

the neighbour cells for cause 13. 63=-47 dBm

OFFSET_RXQUAL_FH 0 to 7 stepsize 0.1 0:70 8

Offset added to quality thresholds 0=070=7

Offset_Hopping_HO 0 to 7 step size 0.1 0:70 8

Offset used in handover quality causes in case offrequency hopping

0=070=7

OFFSET_HO_MARGIN_INNER -127 to +127 dB -127 :+127 8

Offset which allows to take account of the radiodifferences between the inner and the outerzone (especially in multiband cells)

step size 1 dB

ORDER(n) -290 to 260 dB -290:+290 16

Order Evaluation of cell n used for ranking

OUTDOOR_UMB_LEV(0,n) 0 to 63 dBm 0:63 8

minimum receive level to trigger HO towardsumbrella cell n for all emergency causes triggered inlower layer.

step size 1 dBm 0=-110 dBm63=-47 dBm

PMaximum Transmit Power for class of MS and forthe corresponding frequency band (GSM900,DCS1800, DCS1900)

See [18] See [18] 8

PBGT(n) -147 to +97 dB -147:+97 8

Power Budget evaluation of reception

of cell n related to current cell

PING_PONG_HCPDynamic handicap applied to the precedent cell onwhich the call has been (see appx B). Defined on acell basis.

0 to 20 dBstepsize 1 dB

0:20 8

PREC_LAYER_TYPE indefinite,upper, 0 : 3 8



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

indication of the CELL_LAYER_TYPE of thepreceding cell

lower,single 0 : indefinite1 : upper2 : lower3 : single

PREF_LAYERindication of the preferred layer for the target cell

none, upper, lower,upper+single

0:3 ; 0 = none1 = upper2 = lower3 = upper+single

2

PREFERRED_BAND none, GSM or DCS 0 = none 2

Frequency band type where the multiband 1 = GSM

mobiles will be preferably directed 2 = DCS

PRIORITY(n1,n2) 0 to 3 step size 1 0:3 2

Priority of cell n2 when serving cell=n1 0: highest priority

3: lowest priority

RXLEV_DL_IH -110 to -47 dBm 0:63 8

Maximum Receive Level step size 1 dBm 0=-110 dBm

for Downlink (intracell and quality Handover) 63=-47 dBm

RXLEV_UL_IH -110 to -47 dBm 0:63 8

Maximum Receive Level step size 1 dBm 0=-110 dBm

for Uplink (intracell and quality Handover) 63=-47 dBm

RXLEV_DL_ZONE -110 to -47 dBm 0:63 8


for Downlink (Interzone Handover) 63=-47 dBm

RXLEV_LIMIT_PBGT_HO -110 to -47 dBm 0:63 8

Minimum Level above which an handover on power step size 1 dBm 0=-110 dBm

budget is not triggered 63=-47 dBm

RXLEV_UL_ZONE -110 to -47 dBm 0:63 8


for Uplink (Interzone Handover) 63=-47 dBm

RXLEV_DL_FULL -110 to -47 dBm 0:63 6

Measurement of signal level assessed step size 1 dBm 0=-110

over the full set of TDMA frames 0=-47

within an SACCH block on the Downlink

RXLEV_DL_SUB -110 to -47 dBm 0:63 6

Measurement of signal level assessed step size 1 dBm 0=-110

over a subset of 12 TDMA frames within 0=-47

an SACCH block on the Downlink

RXLEV_NCELL(n) -110 to -47 dBm 0:63 6

Receive Level from step size 1 dBm 0=-110




All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

RXLEV_UL -110 to -47 dBm 0:63 6

Measurement of Level on step size 1 dBm 0=-110

the Uplink 63=-47

RXLEVmin(n) -110 to -47 dBm 0:63 8

Minimum allowable received step size 1 dBm 0=-110

Level at the MS from cell n 63=-47

Traffic_load(n) indefinite, low, high 0 : 2 8

Situation of the traffic in the cell n 0 : indefinite1 : low2 : high

U_RXLEV_DL_MCHO -110 to -47 dBm 0:63 8

High threshold of minimum Receive Level step size 1 dBm 0=-110 dBm

for Downlink (Level microcellular Handover) 63=-47 dBm

U_RXLEV_UL_MCHO -110 to -47 dBm 0:63 8

High threshold of minimum Receive Level step size 1 dBm 0=-110 dBm

for Uplink (Level microcellular Handover) 63=-47 dBm

U_TIME_ADVANCE 0 to 63 x 3.69µs 0:63 8

Maximum Distance for Handover

ZONE_HO_HYST_DL -40 to +40 dB 0 : 80 8

Hysteresis downlink for Interzone Handover from theouter

step size 1 dB

zone to the inner zone of a concentric cell ormultiband cell

ZONE_HO_HYST_UL -40 to +40 dB 0 : 80 8

Hysteresis uplink for interzone Handover from theouter zone to the inner zone of a concentric cell or

step size 1 dB

multiband cell

ZONE_TYPE outer or inner 0 : Outer 1

Indicator of cell zone 1 : Inner

4.4.2 Directed retry

The following parameters are used by the directed retry procedure only.

NAME RANGE BIN. RANGE BITS

AV_RXLEV_NCELL_DR(n) -110 to -47 dBm 0:63 8

Average receive level of neighbour step size 1 dBm 0=-110

cell n at MS for forced directed retry 63=-47

AV_RXLEV_PBGT_DR -110 to -47 dBm 0:63 8

Average receive level of serving cell step size 1 dBm 0=-110

at MS for forced directed retry (PBGT) 63=-47



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

EN_DR enable or disable 0 : disable 1

Enable/disable directed retry procedure 1 : enable

EN_EXT_DR enable or disable 0 : disable 1

Enable/disable external directed retry procedure 1 : enable

EN_FORCED_DR enable or disable 0 : disable 1

Enable/disable forced directed retry (cause 20) 1 : enable

FREElevel_DR(n) 0 to 255 TCH channels 0:255 16

Min. threshold of free TCH channels inneighbour cell n for forced directed retry

step size : 1 channel

L_RXLEV_NCELL_DR(n) -110 to -47 dBm 0:63 8

Min. threshold of receive level at MS for step size 1 dBm 0=-110

forced directed retry to neighbour cell n 63=-47

RXLEV_NCELL(n) -110 to -47 dBm 0:63 6

Receive Level from step size 1 dBm 0=-110




All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

4.4.3 Relationships between parameters

The document "BSS telecom parameters" ([13]) specifies also the rules to be fulfilled by the handoverparameters. The present specification is the reference document in case of discrepancy.The default values for parameters are indicated in the document [13].

Each relationship is either mandatory or recommended.The recommended relationships are not checked by an automatic procedure.

Note : - for thresholds relative to quality measurements, the GSM coding is assumed, as already stated,it is contra-intuitive.

- The relationships between the parameters relative to HO preparation and the ones relative toPower control are included. The parameters of power control are characterised by the suffix_P or _PC. For more information about them, refer to [18].

Mandatory relationships

### RXLEV_UL_IH > L_RXLEV_UL_H.

### U_RXLEV_UL_P > L_RXLEV_UL_H.

### RXLEV_DL_IH > L_RXLEV_DL_H.

### U_RXLEV_DL_P > L_RXLEV_DL_H.

### Relations between LOADlevel_i :For i=1 to 3, LOADlevel_i < LOADlevel_i+1

### Relations between LOADfactor_i :For i=1 to 4, LOADfactor_i >= LOADfactor_i+1

### Relations between FREElevel_i :For i=1 to 3, FREElevel_i < FREElevel_i+1

### Relations between FREEfactor_i :For i=1 to 4, FREEfactor_i =< FREEfactor_i+1

### L_LOAD_OBJ =< H_LOAD_OBJ

Recommended relationships

### L_RXQUAL_UL_H >= L_RXQUAL_UL_P.

### L_RXQUAL_DL_H >= L_RXQUAL_DL_P.

### L_RXLEV_UL_H < L_RXLEV_UL_P.

### L_RXLEV_DL_H < L_RXLEV_DL_P.

### A_LEV_HO = 2 * A_LEV_PC.

### A_QUAL_HO = 2 * A_QUAL_PC.

### A_PBGT_HO = 2 * A_LEV_HO



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

• T_FILTER > 0.5 seconds

###ZONE_HO_HYST >= BS_TXPWR_MAX - BS_TXPWR_MAX_INNER

### FREElevel_DR(n) > N_TCH_HO(n).N_TCH_HO(n) is the number of TCH channel reserved in the best interference band (see [16] forfurther details).

### For a microcell configuration, it is recommended :

N_BAD_SACCH = RADIO_LINK_TIMEOUT_BS - N_BSTXPWR_M + 1(for more information, see [18]).

### It is recommended to inhibit Traffic handover towards 1 TRX cells. These cells do not haveenough resources to receive incoming handovers due to congestion of neighbour cells. Moreoverbecause of the great variation of traffic in the 1 TRX cells, their Traffic_load is always different fromlow.

### If PRIORITY(0,n) is used from cell of preferred band to cell of classical band, then it is recommended:EN_PREFERRED_BAND_HO = DISABLE in the classical band cell.

### If PRIORITY(0,n) is applied in order to manage inter-bands handover in a multiband network,then it is recommended:

PREFERRED_BAND = none.

### If PRIORITY(0,n) is used from microcell to macrocell, then it is recommended:EN_RESCUE_UM = INDEFINITE in the microcell.

• For transferring fast mobiles from a minicell n1 to an umbrella cell n2 through a power budgethandover, it is recommended :- if CELL_EV=GRADE

HO_MARGIN(n1,n2)=-127dBLINKfactor(n1,n2)=24dB

### Compatibility checking between cell configurations and handover inhibitionflags.

For the definition of the different cell profiles, see section 2.4

The following relationships are mandatory, whatever CELL_BAND_TYPE.

- Single cell profile

EN_MCHO_NCELL = DISABLE.EN_MCHO_H_DL = DISABLE.EN_MCHO_H_UL = DISABLE.EN_MCHO_RESCUE = DISABLEEN_SPEED_DISC = DISABLE

- Micro cell profile

EN_MCHO_NCELL = DISABLE



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel - Mini cell profile

EN_MCHO_NCELL = DISABLEEN_MCHO_H_DL = DISABLE.EN_MCHO_H_UL = DISABLE.EN_MCHO_RESCUE = DISABLE

- Umbrella cell profile

EN_MCHO_H_DL = DISABLE.EN_MCHO_H_UL = DISABLE.EN_MCHO_RESCUE = DISABLE

- Extended inner and outer cell profile

HO_SDCCH_INHIBIT = DISABLE (SDCCH handovers are disabled)FREElevel_DR = 255 for the serving inner and outer cellEN_MCHO_NCELL = DISABLE.EN_MCHO_H_DL = DISABLE.EN_MCHO_H_UL = DISABLE.EN_MCHO_RESCUE = DISABLEEN_SPEED_DISC = DISABLE

- Concentric cell profile

EN_MCHO_H_DL = DISABLE.EN_MCHO_H_UL = DISABLE.EN_MCHO_RESCUE = DISABLEEN_MCHO_NCELL = DISABLEEN_SPEED_DISC = DISABLE

- Concentric Umbrella cell profile

EN_MCHO_H_DL = DISABLE.EN_MCHO_H_UL = DISABLE.EN_MCHO_RESCUE = DISABLE

### Cells in the preferred band.

If BCCH_FREQ corresponds to GSM band (extended band included) and PREFERRED_BAND= GSM

or if BCCH_FREQ corresponds to DCS1800 or DCS1900 band and PREFERRED_BAND = DCSthen it is mandatory : EN_PREFERRED_BAND_HO = DISABLE.

### Cells having different frequency bands

Cell n1 and cell n2 being adjacents, If BCCH_FREQ(n1) corresponds to GSM band (extended band included)and BCCH_FREQ(n2) corresponds to DCS1800 or DCS1900 band



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

or if BCCH_FREQ(n1) corresponds to DCS1800 or DCS1900 bandand BCCH_FREQ(n2) corresponds to GSM band (extended band included),

then it is recommended:HO_MARGIN_QUAL(n1,n2) = -127 dBHO_MARGIN_LEV(n1,n2) = -127 dBHO_MARGIN_DIST(n1,n2) = -127 dB



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

5. RELEASE CHANGES

Changes from ALCATEL BSS release 2 to ALCATEL BSS release 3

The changes from Release 2 to Release 3 are based on the 3 following features descriptions :

- FD/3/10.6 : Support of microcellular environment. Concepts presented in SYS/006 and SYS/012 areintroducedSYS/006 : definition of parameters for cell environments, H. Brinkmann and G. KreftSYS/014 : handovers in a microcellular environment, C. Cherpantier.

- FD/3/10.7.1 : Concentric cells,- FD/3/10.8 : Directed Retry,- CRQ/298 : improvements for phase 2.1

Inhibition of the feature to transform an intracell HO to an intercell HO,Processing of L1 info in the case where L3 info (measurement report) is missing,The timer T_7 used by the Handover algorithms is renamed T_FILTER.

- CRQ/362 : introduction of conditions PC-9 and PC-10 : power control with good quality and lowlevel.

- CRQ/361 : relationship between MS power control and radio link supervision. When a radio linkrecovery occurs, the MS power control function is resumed immediately.

- clarification about the power control and handover algorithms defined in the ALCATEL BSS. Theseclarifications are based on document ST2/53 "rationale for the power control and handoveralgorithm" from P.Guillier.


The changes from Release 3 to Release 4 are based on the following documents :

- MFD 11.5 Power control and handover algorithm improvements ed 05 :inhibition of radiolink recovery by O&M flagdisabling of ORDER calculation based on number of free TCH by O&M flagEnabling of MS power control and uplink measurements related handover causes in case ofmissing SACCH frames.

- ITCC/TELACT/TEL/PP/006 : remarks made by ITC on specifications for rel 3- fax SDEF/94/HO.001 from Steve DEFOORT on rel3 document inconsistency for the causes HO-8and HO-9.- MFD 10.11 Mobile velocity dependent handover- AMCF/ITD/SAS/CC/1333 : "Description of Release 4 handover algorithms in hierarchical networks"memo by Corinne CHERPANTIER


The changes from Release 4 to Release 5 are based on the following documents :

- TFD 11.22a : Handover algorithm improvements, Multiband Handover- TFD 10.14 : DCS1900 support, Telecom part- Approved Release 4 CRQs : CRQ 1428, CRQ 1705, CRQ 1806, CRQ 1971, CRQ 2027, CRQ 2093,CRQ 2109, CRQ 2144, CRQ 2234, CRQ 2408, CRQ 2472, CRQ 2504, CRQ 2505

Moreover, the original document is partly modified :- Mode A is removed



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

- Section 3 is reorganised, section 2.2 removed- Section 5, ’Release changes’ has been created- Appendix B and F are removed, Appendix C is new

Minor changes are performed on the specifications :- The TFD 11.22a is completed with recommendations on HO_margins and LINKfactors foremergency handovers between cells of different frequency band- Handover causes on quality are rewritten (inversion of the quality comparisons)- Recommendation CELL_EV = ORDER for mini-cell profile becomes mandatory- Handover cause 6 is no longer forbidden for micro-cell profile.- The recommendation for N_BAD_SACCH is modified.


The changes from Release 5 to Release 6 are based on the following documents:

- TFD 11.31: general handover algorithms improvements- TFD 10.8b: external directed retry- TFD 11.22.e: controlled handover in multilayer/multivendor environment- TFD 11.30: traffic management in handover algorithms- TFD 3.19: HSCSD- TFD 11.32: improvements in radio channel selection- Approved Release 5 CRQs 18579, 3028, 2736, 10645, 19733

The section 2 is reorganised. Some descriptions have been put in a new step 1 document (refer to[21]).The section 3.1. Active channel preprocessing, the appendix C are in the new document Radiomeasurements data processing [20].A new handover alarm management is specified in section 3.2.4.

Changes from ALCATEL BSS release 6 to ALCATEL BSS release 6.2

The changes from Release 6 to Release 6.2 are based on the following documents:

- TFD XX.XX: GPRS

6. FEATURES

Release 6 feature list

11.31: general handover algorithms improvements (improvements 2, 3, 4, 5, 6, 7, 10)10.8b: external directed retry11.22.e: controlled handover in multilayer/multivendor environment11.30: traffic management in handover algorithms3.19: HSCSD11.32: improvements in radio channel selection

Release 6.2 feature list

XX.XX: GPRS



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

7. GLOSSARY

7.1 Abbreviations

ARFCN Absolute Radio Frequency Channel NumberBA BCCH-allocationBFI Bad Frame IndicationBS Base StationBSC Base Station ControllerBSIC Base Station Identity CodeBSS Base Station SubsystemBTS Base Transceiver StationdB deciBelDC Direct CurrentDR Directed RetryDTX Discontinuous transmissionDCS-1800 Digital Cellular system using frequency band [1710..1880] MHzDCS-1900 Digital Cellular system using frequency band [1850..1990] MHzFH Frequency HoppingGSM-900 Global System for Mobile communications using frequency band [880..960] Mhz

(extension band G1 inclusive)HO HandoverLOS Line Of SightMSC Mobile Switching CentreMS Mobile StationO&M Operation and MaintenanceOMC Operation and Maintenance CentrePBGT Power BudgetPC Power ControlSACCH Slow associated control channelSADT Structured Analysis and Design TechnicsSDCCH Slow dedicated control channelSDL Specification Description LanguageTCH Traffic channelTCH/FS Traffic channel Full SpeechTCU Terminal Control UnitTOA Time Of ArrivalTRX Transmitter ReceiverTS Technical Specification

Note : all the parameters and variables used in the algorithms are thoroughly described in thededicated sections and in section 4.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

7.2 Definitions

- internal HO : the handover execution is controlled by the BSC (only intracell and intercell-intra-BSCHO).

- external HO : the handover execution is controlled by the MSC (necessary for all intercell-inter-BSCHO, possible for intercell-intra-BSC HO).

- intracell HO : handover between two channels of the same cell.

- intercell HO : handover between two channels of adjacent cells. The old channel belongs to theserving cell, the new channel to the target cell.

- intra-BSC HO : the serving cell and the target cell belong to the same BSC.

- interzone HO : intracell handover between the inner zone and the outer zone of a concentric ormultiband cell configuration.

- intrazone HO : intracell handover within a zone (inner or outer) of a concentric or multiband cellconfiguration.

- directed retry : handover from SDCCH to TCH when the serving cell is congested at the startingtime of the assignment procedure.

In this release of the ALCATEL BSS, the directed retry is internal or external to the BSS.

- decibel unit :The "decibel" is a unit currently used in radio communications. It is the logarithmic expression of theratio of two terms :

N dB = 10 log10(P1/P2) with P1, P2 = signal power.

M dB = 20log10(V1/V2) with V1, V2 = signal voltage.

The "dB" is the usual unit for the gains of power or voltage.

The dBm is a variant of the dB unit :Power expressed in dBm = 10 log10(P) with P expressed in mW.Ex : 1W corresponds to 30 dBm. 1pW (10-9 mW) corresponds to -90dBm.

The dBW is a variant of the dB unit :Power expressed in dBW = 10 log10(P) with P expressed in W.Ex : 10W corresponds to 10 dBW.

The dBi is a variant of the dB unit which is currently used for the antenna gains. The index "i" means"isotropic" as an antenna gain is referred to the gain of an isotropic antenna (same gain in alldirections).

- log normal fading : The signal attenuation during propagation is the product of small independentattenuations. Expressed in dB, this attenuation becomes a random variable which has a normal (orgaussian) pdf, (central limit theorem). The log normal fading is defined as a centred (mean value is 0)gaussian variable that must be added to the mean signal value resulting from propagation attenuationin order to have the reported value of the signal level (by MS or BS).The log normal fading standard deviation ### normally ranges about 6-7 dB in urban macrocellularenvironment and about 5 dB for rural environment.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

Appendix A

(2 pages)

Power budget equation

The Power budget criterion PBGT is used to estimate the difference of path loss between twoneighbouring cells.

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)

PBGT_DR(n) = AV_RXLEV_NCELL_DR(n) - AV_RXLEV_PBGT_DR- (BS_TXPWR_MAX - AV_BS_TXPWR_DR)- (MS_TXPWR_MAX(n) - MS_TXPWR_MAX)

with :

- AV_RXLEV_NCELL(n) : average of RXLEV_NCELL(n) over A_PBGT_HO or A_PBGT_DRmeasurements (neighbour cell(n)).

- AV_RXLEV_NCELL_DR(n) : average of RXLEV_NCELL(n) over A_PBGT_DR measurements(neighbour cell(n)).

- AV_RXLEV_PBGT_HO : average of the received levels RXLEV_DL_FULL or RXLEV_DL_SUBover A_PBGT_HO measurements (serving cell).

- AV_RXLEV_PBGT_DR : average of the received levels RXLEV_DL_FULL or RXLEV_DL_SUBover A_PBGT_DR measurements (serving cell).

- BS_TXPWR_MAX : max power of the BTS in the serving cell (fixed value for each BTS).- AV_BS_TXPWR_HO : average of the BS_POWER values over A_PBGT_HO measurements.- AV_BS_TXPWR_DR : average of the BS_POWER value over A_PBGT_DR measurements.- MS_TXPWR_MAX(n) : max power level the MS is allowed to use in its neighbour cell(n).- MS_TXPWR_MAX : max. power the MS is allowed to use in the serving cell.- PING_PONG_MARGIN(n,call_ref) is a penalty put on the cell n if :

it is the immediately precedent cell on which the call has been,this cell belongs to the same BSC as the serving cell,the call has not performed a forced directed retry towards the serving cell,less than T_HCP seconds have elapsed since the last handover.In this case PING_PONG_MARGIN(n,call_ref) = PING_PONG_HCP.,If the call was not precedently on cell n, or if the preceding cell was external, or ifthe call has just performed a forced directed retry, or if the timer T_HCP hasexpired, then PING_PONG_MARGIN(n,call_ref) = 0

With abstraction of the PING_PONG_MARGIN, which is purely a handicap given to the preceding cellfor a certain time, the PBGT can be described in two steps :



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

### ###BCCH = AV_RXLEV_NCELL(n) - (AV_RXLEV_PBGT_HO + C)with C = BS_TXPWR_MAX - AV_BS_TXPWR_HO.

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

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

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

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

Two reasons (which are not completely decorrelated) for not using the BS powers can be envisaged :- for a given cell, the GSM does not specify formally the maximum BS power of the neighbouring

cells. Only BS_TXPWR_MAX is defined (it is sent on the air interface),- it is not easy for the evaluating BSC to know the maximum BS powers of the neighbouring cells.

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

PBGT >0 : the neighbour cell is more advantageous as the path loss is less than in the current cell.PBGT <0 : the serving cell is more advantageous as the current cell.

The PBGT equation (without temporary handicap) can be interpreted in another way.

PBGT = ###BCCH - ###TXPWR

The PBGT is a balance or a trade-off between two opposite indicators. As a matter of fact :### ###BCCH > 0 : the neighbouring cell n is more advantageous than the serving cell as the

reception of BCCH is better.

### ###BCCH < 0 : the neighbouring cell n is more disadvantageous than the serving cell.

### ###TXPWR > 0 : the neighbouring cell n is more disadvantageous than the serving cell as themaximum permissible power of the MS is higher.

### ###TXPWR < 0 : the neighbouring cell n is more advantageous than the serving cell.

The PBGT can be seen as a balance, at MS side, between a probability to have a better receptionand the probability of requests of transmission at higher levels in the neighbouring cells.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

Appendix B

(1 page)

Recapitulation of the cell types allowed for the serving and the candidate cell for each handovercause

Handover causes Serving cell / zone types Target cell / zone types

Too low quality uplink (cause 2) All All cells except serving cell (1)Too low level uplink (cause 3) All All cells except serving cell (1)Too low quality downlink (cause 4) All All cells except serving cell (1)Too low level downlink (cause 5) All All cells except serving cell (1)Too long distance (cause 6) All All cells except serving cell (1)Bad SACCH frames (cause 7) CELL_DIMENSION_TYPE =

microAll cells except serving cell (1)

Too low level uplink, inner zone(cause 10)

CELL_PARTITION TYPE =concentric

ZONE_TYPE = inner

Same cellZONE_TYPE = outer

Too low level downlink, inner zone(cause 11)

CELL_PARTITION TYPE =concentric

ZONE_TYPE = inner

Same cellZONE_TYPE = outer

Power budget (cause 12)

(CELL_LAYER_TYPE = singleor

CELL_LAYER_TYPE = upper)

CELL_LAYER_TYPE =singleor

CELL_LAYER_TYPE = upperSame CELL_BAND_TYPE

The MS is not in the inner zoneof a multiband cell

CELL_LAYER_TYPE = lower CELL_LAYER_TYPE = lowerorupper (if MS_SPEED = fast)

Same CELL_BAND_TYPE

Power budget (cause 12)The MS is in the inner zone of amultiband cell

(CELL_LAYER_TYPE = singleor

CELL_LAYER_TYPE = upper)

(CELL_LAYER_TYPE =singleor

CELL_LAYER_TYPE = upper)and

FREQUENCY_RANGE=GSM-DCS

CELL_LAYER_TYPE = lower (CELL_LAYER_TYPE = lowerorupper (if MS_SPEED = fast))

andFREQUENCY_RANGE=GSM-

DCSToo high level uplink or downlinkouter zone (cause 13)

CELL_PARTITION_TYPE =concentric

ZONE_TYPE = outer

Same cellZONE_TYPE = inner

High level in neighbour lower layercell for slow mobile(cause 14)The MS is in the inner zone of amultiband cell

CELL_LAYER_TYPE = upperCELL_LAYER_TYPE = lower

and(EN_BI-

BAND_MS(n)=ENABLE orCELL_BAND_TYPE(n) <>

CELL_BAND_TYPE(0))



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

High level in neighbour lower layercell for slow mobile(cause 14)The MS is not in the inner zoneof a multiband cell

CELL_LAYER_TYPE = upperand

CELL_BAND_TYPE =PREFERRED_BAND

CELL_LAYER_TYPE = lowerand

(EN_BI-BAND_MS(n)=ENABLE orCELL_BAND_TYPE(n) =

PREFERRED_BAND)High level in neighbour lower layercell for slow mobile(cause 14)The MS is not in the inner zoneof a multiband cell

CELL_LAYER_TYPE = upperand

CELL_BAND_TYPE <>PREFERRED_BAND

CELL_LAYER_TYPE = lower

Too high interference level uplink(cause 15)

All Same cell

Too high interference leveldownlink (cause 16)

All Same cell

Too low level uplink compared toHigh Threshold (cause 17)

CELL_DIMENSION_TYPE =micro

All cells except serving cell (1)

Too low level downlink comparedto High Threshold (cause 18)

CELL_DIMENSION_TYPE =micro

All cells except serving cell (1)

Forced directed retry (cause 20) All All cells except serving cellHigh level in neighbour cell in thepreferred band (cause 21)



Too short distance (cause 22) CELL_RANGE = extendedouter

All cells except serving cell

Traffic handover (cause 23)The MS is not in the inner zoneof a multiband cell

CELL_LAYER_TYPE = singleor

CELL_LAYER_TYPE = upper


CELL_LAYER_TYPE = upperSame CELL_BAND_TYPE

CELL_LAYER_TYPE = lower CELL_LAYER_TYPE = lowerSame CELL_BAND_TYPE

Traffic handover (cause 23)The MS is in the inner zone of amultiband cell

CELL_LAYER_TYPE = singleor

CELL_LAYER_TYPE = upper


CELL_LAYER_TYPE = upperandFREQUENCY_RANGE=GSM-DCS

CELL_LAYER_TYPE = lower CELL_LAYER_TYPE = lowerandFREQUENCY_RANGE=GSM-DCS

General capture handover (cause24)The MS is in the inner zone of amultiband cell

All EN_BI-BAND_MS(n)=ENABLEor

CELL_BAND_TYPE(n) <>CELL_BAND_TYPE(0)

General capture handover (cause24)The MS is not in the inner zoneof a multiband cell


EN_BI-BAND_MS(n)=ENABLEor

CELL_BAND_TYPE(n) =PREFERRED_BAND

General capture handover (cause24)The MS is not in the inner zoneof a multiband cell


All cells except serving cell

GPRS redirection (cause 25) All EN_GPRS(n)=TRUE



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

notp

erm

itted

with

outw

ritte

nau

thor

izat

ion

from

Alc

atel

(1): The serving cell is a canidate cell if the MS is connected to the inner GSM 1800 zone of amultiband cell.



All

right

s re

serv

ed. P

assi

ng o

n an

d co

pyin

g of

this

do

cum

ent,

use

and

com

mun

icat

ion

of it

s co

nten

ts

not p

erm

itted

with

out w

ritte

n au

thor

izat

ion

from

Alc

atel

.

Appendix C

(1 page)

Compliancy with the GSM requirements

Handover algorithm

As stated in [2] : "the exact handover strategies will be determined by the network operator".Document [2] provides also a "detailed example of a basic overall algorithm" which is the basis ofthe one implemented in the ALCATEL BSS.The complete ALCATEL algorithm is described in section 3.2 of this document.

For further details about the compliance of this function with the requirements of the GSM TechnicalSpecification 05.08 ([2]), see [4].

Directed retry algorithm

GSM has not specified any requirement. The algorithm is implementation dependent.

END OF DOCUMENT

Alcatel Ho 2g Preparation

Documents

Transcript of Alcatel Ho 2g Preparation