ps irat u2g optimization 2

8/9/2019 PS IRAT U2G Optimization 2

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Ps irat(u2g) optimizationsupport


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PS IRAT (UMTS to GSM ) Success Rate The KPI defnes the success rate or PS Inter RAT cell change attempts or U

on dedicated channel! "uring Inter#RAT$$ rom UTRA% to &PRS' U on "$'the andoer ealuation unction triggers this unction to indicate that *e

need to ma+e handoer to a &S, cell!

PS IRAT SUCCESS RATE =

pm%o-utIrat$cSuccess.pm%o-utIrat$cAtt

I%TR-"U$TI-%


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/lo*chart or IRAT$$ rom UTRA% to&PRS


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› To start *ith ' %eigh0our 1ist Tuning has to 0e done! Prominent 2&neigh0ours should 0e added and /ar#o neigh0ours should 0e deleted!

› 3& cells *ith er4 lo* num0er o 2& relations hae to 0e identifed ! It ispreerred to hae atleast 5 gsmrelations per utrancell!

› Proper Selection Priority or gsmrelations has to 0e gien 0ased on 2

2& andoer ,atri6 'Tier and distance!The colocated 2& cell' 2& cells othe same site and TIR 7 neigh0ours should 0e gien selection priorit4 as7' selection priorit4 as 2 to TIR 2 neigh0ours and so on!

› The 2& defnitions li+e 1A$ ' $I' 8$$' 8SI$ hae to 0e chec+ed i the4 aredefned correctl4 in the R%$.,SS or not!

› To chec+ 2& defnitions in the R%$' *e can use ollo*ing command line inthe R%$#

get externalgsmcell = GSM Cell Name

This has 0een illustrated *ith an e6ample in the ne6t slide

STPS /-R PS IRAT -PTI,I9ATI-%


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› Ater all neigh0our tuning' chec+ing cell defnitions has 0een done ' it has to

0e chec+ed i the IRAT ailure is occuring or some particular gsmrelations!-0sering trends o pm%o-utIrat$cSuccess and pm%o-utIrat$cAtt perutrancell per gsmrelation can help in fnding such *orst gsmrelations

› Ater the *orst gsmrelations identifcation has 0een done ' *e should chec+the pac+et channel allocation attempts and pac+et channel allocationailures !The 2& counters or fnding the same are:

PCA!!ATT or Num"er o# $ac%et c&annel allocation attem$ts andPCA!!'AI! or Num"er o# $ac%et c&annel allocation #aile

› ard 8loc+ing and Sot 8loc+ing in the *orst gsmrelations hae also to 0echec+ed !igh pac+et channel ailure implies 2& congestion!

Identi4ing *orst gsmrelations


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$-%&STI-% I% 2& $11S

The counter pmNoOutIratCcReturnOldCh has also to be verified. This counter provides the

total number of the PS Inter-RATCC attempts for UE on C! "here the UE returns to oldchannel. It is stepped for Inter-RATCC from UTRA# to $PRS% UE on C!. The counter is

increased "hen the &Cell chan'e order from UTRA# failure( RRC messa'e is received from the

UE. ONE REASON FOR RETURN TO OL C!ANNEL "#$e %&' IS !I&! (C! ALLOCATION

FAILURE$

To improve PS IRAT in such cases% follo"in' actions mi'ht be ta)en*

+.,$ con'estion has to be resolved "hich can be done b allocatin' more PC! channels . In

cases of etreme con'estion% additional TR/s ma be installed.

,.0$ parameters can be retuned to tri''er IRAT from 0$ to ,$ onl "hen 0$ covera'e becomes

ver poor and ,$ radio conditions are ver 'ood. The parameters to be tuned have been

eplained in the upcomin' slide.


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-ptimizing 3& parameters

› 84 lo*ering the alue o the parameters li+e serice*+est,EcNo andsericeo+set,Rsc$ *e can dela4 the compress mode and can aoidunnecessar4 compress mode !The counters pmcmattdlhls and pmcmsuccdlhlscan 0e used to fnd the num0er o 1S attempts and success respectiel4! Thealue o the parameter -gsmt&res&.a/ can also 0e increased to trigger IRAT onl4*hen 2& radio conditions are er4 good! This *ill reduce PS IRAT attempts and*ill also improe PS IRAT success rate! An e6ample o the parameter settings is:

gsmt&res&.a can 0e increased to #;<

serice*+est,EcNo to #3 sericeo+set,Rsc$ to #= (The setting o these parameters ma4 ar4 rom net*or+ to net*or+)

› o*eer 'it is adisa0le to change serice osets onl4 or ollo*ing UeRC states01231245,635,641235,6 an 5,6312

› I the PS IRAT remains poor een ater tuning the a0oe parameters and addingadditional P"$ ' then NEGATI7E IN8I7I8UA! *''SET can 0e set or someparticular *orst gsm relations! o*eer' this *ill aect $S IRAT as *ell so careshould 0e ta+en o!

› The I$, 0ands in 2& hae also to 0e chec+ed!


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I$, 0and

ICM 9AN8:INTR*8UCTI*N

I ICM is actie' &PRS.&PRS $hannel Administration can use the ran+ing ochannels into intererence 0ands as helpul inormation *hen selectingchannels rom the circuit s*itched domain to 0e confgured as dedicated oron#demand P"$s! >hen a P"$ is reconfgured to a T$' the channel isplaced in the intererence 0and it *as in 0eore it *as allocated as P"$! Idle

$hannel ,easurements are not perormed on P"$s ! /or idle channelmeasurement there are our o0?ect t4pes or /R.R and -1.U1 i!e -erlaidand Underlaid! In these o0?ect t4pes there are counters or the accumulatednum0er o idle channels in each intererence 0and iz! IT'USI9i4ITUSI9i4IT'*SI9i 4IT*SI9i i as 7'2'!!!'=!

RE!ATE8 ;PIs

IT/-SI87 @ IT-SI87 *! ICM 5' IT/-SI82 @ IT-SI82 *! ICM ,4

IT/-SI83 @ IT-SI83 *! ICM .'IT/-SI8B @ IT-SI8B *! ICM 2'

IT/-SI8= @ IT-SI8= *! ICM


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$orrelating icm 0and *ith PS IRATSU$$SS RAT

I I$, 8and is sho*ing high alue in I$, 8and B (*hich is a0oe #;C d8m) and

I$, 8and =(*hich is a0oe #CCd8m) ' then there is defnitel4 some source oe6ternal intererence in the 2& cell and this ma4 also cause PS IRAT /AI1UR inthe cells! A spectral scan using Spectrum Anal4ser should 0e done in highintererence cells! >e can also use 8and Pass flter or $",A flter to resolethe issue!

The screenshots 0elo* sho* t*o cells o Aircel DEK *here I$, 8and B and I$,

8and = are sho*ing high alues and corresponding PS IRAT Success rate arealso er4 lo*! Its pro0a0le that 0ecause o e6ternal intererence in the 2& cell'the PS IRAT attempts are not 0ecoming successul!


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2& PARA,TR#I$,STAT

› The parameter ICM STATE also needs to 0e chec+ed ICM STATE is aparameter defned in the 8S$ that sets the idle channel measurements toACTI7E4 PASSI7E or N*A!!*C N*A!!*C means that the idle channelmeasurements are used or statistics onl4' and not or channel allocation!

REC*MMEN8E8 7A!UE

Some additional 0$ parameters and counters that can be chec)ed for PS IRAT optimi1ation

have been eplained in the net fe" slides.


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Parameter# 'smAmountPropRepeat

› This parameter decides ho" man times R#C "ill command UE to re-attemptcell chan'e to the $S2 cell repeatedl based on the same measurement report

ecludin' the first attempt. A fe" UEs under such circumstances contribute

hi'hl in the of count of pmnooutiratccatt and ma cause lo" PS IRAT Success

Rate.

› So the parameter )*mAmount(ropRepeat "hich is 'enerall set to 3 can bereduced to , or +.This "ill reduce IRAT attempts and "ill also improve PS IRAT

success rate.

› The functionalit of this parameter can be "ell understood from the flo"chart'iven in the net slide


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F%T 3a


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Parameter # fach2eas4ccaCc5enCoeff

› 'ac& Measurement *ccasion Cycle !engt& coe>cient # A actor used*hen the U perorms inter#reGuenc4 and inter#s4stem measurements! TheU uses this parameter to calculate the interal length in order to determinethe repeating c4cle o the measurement!

› Falue mapping:

? : not 0roadcasted in SI8 77!

5 : not used!

, : not used!. : used *hen inter reGuenc4 and &S, neigh0ors!

2 : used *hen inter reGuenc4 or &S, neigh0ors!

< : 5, not used!

I #ac&Meas*ccaCyc!enCoe+ is set to


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Pd $ounter#P,PR-PA&ATI-%"1AH

› The pd counter pmPropagation"ela4 can 0e used to o0sere samples o a cell ! I acell is sering at a er4 long distance' then phsical optimization ma4 also help toreduce the num0er o PS IRAT attempts!

› 6ample: Ater do*ntilting the cell U99?@5(9URNC5:Aircel)'the irat attemptsreduced rom as high as J7


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Issue o Rau re?ection.ailure

› The LRAU Re?ectionM during IRAT - ma4 also cause lo* PS IRAT handoersuccess rate!

› The occurances o RAU re?ection can 0e +no*n rom S&S% trace or rom the

"rie test log fles !The T,S "T fles sho*s Rauting Area Update/ailure.Re?ect

INSTANCE OF RAU RE+ECTION ,!ILE UE IS IN 2&

RAU RE-UEST

6I% 2&: 13 ,S& : "TAI1S S-> 0 T&e mo"ile station oes not su$$ort t&e PSanoer I such issues are o0sered' there is a high pro0a0ilit4 that the issue ismainl4 rom the core side and it needs to 0e chec+ed!


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UTR' U TRA$I%&

› Timestamp lh U R8S R%$ $% Prot ,essage› :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::› B?,0,?0561


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TA%K H-U

ps irat u2g optimization 2

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