Performance Troubleshooting -PS - GPRS Attach v0.1

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BSS PerformanceTroubleshooting Instructions

GPRS Attach

Version 0.1


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2 Copyright 2007 o!ia Siemens et"or!s#All rights reser$e%#

DOCUMENT DESCRIPTION

Title an% $ersion Performance troubleshooting instructions & BSSReference

Target Group P' engineers ("or!ing in 'A pro)ects*

Technology an%S+ release

2G, 2#-G

Relate% Ser$iceItems

Ra%io net"or! optimi.ation / Capacity 1tension anagement

Ser$ice Itemnumber

Author 3arri Sunila

4ate &Appro$er ric 3roon

CHANGE RECORD

This section pro$i%es a history of changes ma%e to this %ocument

VERSION DATE EDITED BY SECTION/S COMMENTS

0#5 52#06#2050 3arri Sunila A 8irst %raft9

Copyright : o!ia Siemens et"or!s# This material, inclu%ing %ocumentation an% anyrelate% computer programs, is protecte% by copyright controlle% by o!ia Siemens et"or!s#All rights are reser$e%# Copying, inclu%ing repro%ucing, storing, a%apting or translating, anyor all of this material re;uires the prior "ritten consent of o!ia Siemens et"or!s# This

material also contains confi%ential information "hich may not be %isclose% to others "ithoutthe prior "ritten consent of o!ia Siemens et"or!s#


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Table of Contents

Table of Contents##############################################################################################

5# Purpose an% Scope############################################################################

2# GPRS obility management##############################################################

2#5 GPRS Attach###################################################################################################################

2#2 GPRS Attach 3PIs###########################################################################################################2#6 Referencing 3PIs to be chec!e%#####################################################################################

6# Troubleshooting##################################################################################

6#5 Alarms#############################################################################################################################6#2


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= Copyright 2007 o!ia Siemens et"or!s#All rights reser$e%#

5# Purpose an% Scope

Purpose:

This %ocument is an optimi.ation gui%eline "ith the purpose to instruct P'engineers "or!ing in 'A pro)ects to %eli$er performance troubleshooting#

This %ocument is meant for ITRA >S '?

Scope:

The scope of the %ocument is the follo"ing9

To sho" ho" to troubleshoot cells to impro$e certain 3PIs#

NoteAll the net"or!s are %ifferent an% thus is hea$ily recommen%e% to analy.enet"or! properly before optimi.ation# Also properly optimi.ation strategy shoul%be create%, "ill it be better to use special cell le$el optimi.e% parameter $aluesan% loose control of the net"or! or use some general (not cell le$el optimi.e%*$alues#


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- Copyright 2007 o!ia Siemens et"or!s#All rights reser$e%#

2# GPRS obility management

GPRS obility anagement (G* han%les the subscribers@ re;uests forattaching to or %etaching from the General Pac!et Ra%io Ser$ice (GPRS*

net"or!# G up%ates the location of the subscriber to the ome ocationRegister (R* an% to the isitor ocation Register (R* if the obile Station(S* is also attache% to the circuit&s"itche% (CS* ser$ices#

transfers the necessary information from another SGS/Pac!et Processing>nit (PAP>* "hen the subscriber mo$es from one routing area to another# also han%les the subscriber@s authentication functions#

It is important to monitor the performance of G in a GPRS net"or! as thefunctions of G proce%ures are to control the accessibility an% retainability#

GPRS attach success ratio is one of the most important G relate% 3PIs to bemonitore%#

2#5 GPRS Attach

The GPRS Attach is a process %uring "hich the mobile %e$ice informs thenet"or! about its presence in the net"or!# The %e$ice usually initiates the GPRSattach after po"er on# obile state is changing from i%le to rea%y, as can be seenfrom figure belo"# 4etach means that mobile state is changing bac! to i%le#

2#2 GPRS Attach 3PIs

A S shall perform a GPRS Attach to the SGS in or%er to obtain access to theGPRS ser$ices# If Gs interface a$ailable an% the net"or! operates in et"or!

'peration o%e I, the Combine% GPRS/ISI Attach proce%ure "ill be performe%,else, a normal GPRS Attach proce%ure shall be performe%#


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Copyright 2007 o!ia Siemens et"or!s#All rights reser$e%#

The start of a GPRS attach proce%ure is %efine% as "hen the S sen%s a GPRSAttach Re;uest message to the SGS# This proce%ure en%s "hen the S sen%sAttach Complete message to the SGS or the SGS sen%s Attach Re)ectmessage to the S#

The optimal GS net"or! from PS+ ser$ices point of $ie" has9

o As high signal le$el as possible

It means that e$en the in%oor signal le$el shoul% be high enough to

ha$e CSD for getting the highest %ata rate on RC/AC layer#o As lo" interference as possible

The aim of ha$ing high C/I is to a$oi% throughput re%uction base% on

interference#o nough capacity

nough har%"are capacity is nee%e% to pro$i%e the re;uire% capacity

for PS+ ser$ices in time# Both CS+ an% PS+ traffic managementshoul% be harmoni.e% "ith the layer structure an% long term plans#

o As fe" cell&reselection as possible

The %ominant cell co$erage is important to a$oi% unnecessary cell&

reselections in mobility# The pru%ent PC> allocation can help to re%ucethe inter PC> cell reselections#

4ominant cell structure can help to ma1imi.e the signal le$el an%

re%uce the interference, too#o 8eatures

o

All the features shoul% be use% "hich can impro$e the PS+ ser$ice co$erage,

capacity an% ;uality in general#

+ith follo"ing 3PIs GPRS attach success ratio can be monitore%9

o Gb GPRS Attach Success Ratio, 2 (sgsnE-07a*, FH

o Gb GPRS Attach Success Ratio (sgsnE-Dc*, FH

o Gb Combine% Attach Success Ratio, 2 (sgsnE-0Da*, FH

o Gb Combine% Attach Success Ratio (sgsnE-0c*, FH

NoteAll the GPRS attach relate% counters an% counter relate% re)ect causes canbe seen from chapter2#7

Typical reasons for GPRS Attach problems are

o Some Ser$ice is not allo"e% / pro$isione%

o Poor ra%io con%itions


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2#6 Referencing 3PIs to be chec!e%

In follo"ing chapters some 3PIs, "hich shoul% be monitore% "hen analy.ingGPRS attach problems are mentione%

There are many times se$eral reasons for 3PI %egra%ation, so all step shoul% bechec!e% to be sure that reasons for GPRS attach problems "ill be foun%#

2#6#5 8R*from each co%ec of each TRJ in the BTS## In this %ocument ;uality (4 an% >* ismeasure% using BR measurements#

Ba% ;uality is effecting hea$ily on PS 3Pis# In this chapter it is sho"n ho" ;ualitycan be measure% an% ho" to analy.e if ;uality is on reason "hich is causing PS3PI %ecreasing in the net"or!# In Troubleshooting chapter more %etaile%information, ho" to analy.e ba% ;uality is %escribe%

RJ le$el K ;uality %istribution can be seen belo"# The %istribution (lo"est picture*sho"s that there are ;uite a lot ba% ;uality samples "hich "ill cause problems inthe net"or!#

o oice ;uality "ill be %ecrease%

o PS ;uality (throughput * "ill be %ecrease%

o 4ominance areas are not "or!ing properlyo 4rops L ' failures "ill be increase%


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Copyright 2007 o!ia Siemens et"or!s#All rights reser$e%#

2#6#2 Co$erage (R1Ee$elEStatistics table*

Ba% co$erage means that recei$e% signal le$el is near the (S/BS* sensiti$ityle$el# ere the ;uality "ill be %ecrease% %ue to ba% signal le$el an% li!e ba%;uality, this ba% ;uality "ill cause user percei$e% problems#

Ba% co$erage, li!e ba% ;uality, is effecting hea$ily on PS 3PIs# If there are ba%co$erage %ips in the cell, ;uality "ill be %ecrease% an% call "ill be %roppe%# Introubleshooting chapter more %etaile% information ho" to analy.e ba% co$erage

is %escribe%#

See picture belo", ba% co$erage samples are %ue to ba% co$erage#

oteM It shoul% be chec!e% that there is no imbalance problems bet"een > an%4# any times > is the "ea!er one, so > co$erage shoul% be also chec!e%#


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D Copyright 2007 o!ia Siemens et"or!s#All rights reser$e%#

2#6#6 GPRS Attach 8ailure Causes 4escriptions an% Analysis

The purpose of the Reject Cause information element is to in%icate the reason"hy a re;uest from the mobile station is re)ecte% by the net"or!#

ore %etaile% information can be seen from chapter2#7

Troubleshooting

There are many times se$eral reasons for 3PI %egra%ation, so all step shoul% bechec!e% to be sure that reasons for %roppe% calls "ill be foun%#

In chapterrror9 Reference source not foun%an% rror9 Reference source not

foun%some cause $alues "ith e1amples are gi$en# These cause $alues arestrongly recommen%e% "hen analy.ing GPRS attach problems

2#= Alarms

Chec! that there are no any NN or NNN acti$e alarms# Connection to etAct isnee%e%#

2#-


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an%o$er Threshol% Parameters, le$el, ;uality, interference# Threshol%

$alues an% P1,1 $alues can be a%)uste%

ormally some o$erlapping e1ists, so 's to a%)acency, reasons

;uality/Interference "ill happen#

Chec!e% that no missing a%)acency cells# issing neighbors can beone reason for ba% ;uality, ser$ing areas are not "or!ing properly#

If AR feature can be use%, an%o$er Threshol% Parameters, le$el,

;uality, interference# Threshol% $alues an% P1,1 $alues can bea%)uste% little more loose#

o If ba% ;uality in ba% signal le$el,(Q&500%B*

Ba% ;uality %ue to ba% co$erage#

Impro$e co$erage, see 2#

Chec! also imbalance bet"een > an% 4# +hich co$erage > or 4

is more important to impro$e Parameters (R1 e$ in Cell (S*, R1 e$ Access in (RJP** can be

a%)uste% to a$oi% call setups / 's in $ery ba% co$erage#

o Bro!en components, ;uality results are strange, see picture belo"


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o If ba% > signal le$el,(Q&500%B* samples #

Chec! imbalance bet"een > an% 4# If lots of > imbalance, >

co$erage impro$ement can impro$e net"or! performance#o A%% A to impro$e > co$erage

o Chec! that recei$er is "or!ing properly, no bro!en components

o If ba% 4 signal le$el,(Q&500%B* samples #

Chec! imbalance bet"een > an% 4# If lots of 4 imbalance, 4

co$erage impro$ement can impro$e net"or! performance#o Chec! that transmitter is "or!ing properly, no bro!en

componentso Chec! that po"er parameter (PAJ* is correct

o If no imbalance an% ba% co$erage

Impro$e co$erage by a%%ing R8 components

o A%% more gain antennaso >se 8le1i BTS

o A%% ne" sector

o A%% ne" site

Parameters (R1 e$ in Cell (S*, R1 e$ Access in (RJP** can be

a%)uste% to a$oi% call setups / 's in $ery ba% co$erage#

o Bro!en components (lots of sample Q&500%B*, see picture belo"

Almost all > samples in ba% co$erage# 4 is "or!ing fine +

problems, bro!en combiner, TRJ etc# o alarms#

2#7 GPRS Attach 8ailure Causes 4escriptions an% Analysis

The purpose of the Reject Cause information element is to in%icate the reason"hy a re;uest from the mobile station is re)ecte% by the net"or!#

All the GPRS attach relate% counters (1cel* an% counter relate% re)ect causes(6GPP specific cause $alues, +or%* are mentione% belo", see attache% files

GPRS mobilitymanagement - count

3GPP specifc Causevalues.doc

8ollo"ing %ocument is collecte% from 6GPP %ocument9


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o obile ra%io interface ayer 6 specification Core net"or! protocols Stage 6

(6GPP TS 2=#00 $ersion D#5#0 Release D*

http9//"""#6gpp#org/ftp/Specs/html&info/2=00#htm

2#7#5 Cause $alues & Some troubleshooting e1amples

o 8or user subscription relate% failures (for e1ample causes 5- an% 7*, "e may

nee% the support from other parties to impro$e the success rate, e#g#customer ser$ices to offer ser$ice upgra%e to those 2G subscribers "ho areusing 6G phones, etc#

o 8or net"or! relate% failures (for e1ample cause 57*, "e can %o further

analysis "ith protocol analy.ers, there are a number of information that "eha$e to !no" before the troubleshooting starts, i#e#

ISI K chec! "hether the failures are from home subscribers or

roaming subscribers

Signalling flo" K chec! the attach failures occurs at "hich stage of the

proce%ure

o 8or roaming subscribers "ith failure cause co%e 57, re;uest the support from

operation team to $erify the connecti$ity to the roaming partnerss net"or!

o 8or home subscribers "ith failure cause co%e 57, chec! the signaling flo" of

the attach proce%ure, some e1amples of the failures are9

Attach Re)ect sent imme%iately after Attach Re;uest message from >

o chec! the connecti$ity to R

Attach Re)ect sent after RAAP K Security o%e Comman% (Security

o%e Complete message not recei$e%*

o 8urther troubleshoot at the RA

o Protocol errors (Cause co%es D,DD,500,555* might happen %ue to poor ra%io

con%itions (Ba% ;uality, ba% co$erage*

2# SGS/GGS

SGSG / GGS relate% %ocuments can be chec!e% from IS#

3PI gui%line for SGShttps9//sharenet&ims#insi%e#no!iasiemensnet"or!s#com/'pen/6--070-

PS core optimi.ation guil%leline
https://sharenet-ims.inside.nokiasiemensnetworks.com/Open/358507056https://sharenet-ims.inside.nokiasiemensnetworks.com/Open/358507056


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https9//sharenet&ims#insi%e#no!iasiemensnet"or!s#com/'$er$ie"/46D--D52=

PS core optimi.ation training material#https9//sharenet&ims#insi%e#no!iasiemensnet"or!s#com/'pen/=5507-26
https://sharenet-ims.inside.nokiasiemensnetworks.com/Overview/D395591264https://sharenet-ims.inside.nokiasiemensnetworks.com/Open/411075236https://sharenet-ims.inside.nokiasiemensnetworks.com/Overview/D395591264https://sharenet-ims.inside.nokiasiemensnetworks.com/Open/411075236

Performance Troubleshooting -PS - GPRS Attach v0.1

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