3g cell optimisation revab

8/12/2019 3G Cell Optimisation RevAB

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INTRODUCTION

Objective

Statistical RNC/RXI/RBS counters reflect the performance of a 3G cell within thenetwork. Specific counters are analysed to detect arious faults. !he o"#ectie of the

procedure is therefore to trace any network$related faults to the source of the pro"lem"y analysin% the fault symptoms eident in the counter alues.

Scope!his procedure identifies and recommends solutions for network faults identifiedthrou%h the analysis of RNC/RXI/RBS statistical counters.

References&dditional references to this procedure are as follows'

&()X (i"raries'o Radio Network Controller *RNC+ 3,- *CX 0- 1-- RXX+

o RXI ,1 &!2 R.- *CX 0- -1/3 RXX+

o Radio Base Station *RBS+ 311/314/31/3-1 *CX 0- ,--/X RXX+

o 5C62& R&N *CXS -- 4/ RXX+

!)2S 7ser8s 2anual

9or RNC/RXI/RBS counter descriptions refer to the erformance Statisticsdocument within the releant RNC/RXI/RBS &()X (i"rary.

PROCEDURE

ANALYSING COUNTERS

1. Available on an RNC, RXI and RBS basis, the FACTS tool is available tointerface to and represent the relevant counters. Counters are collected on auarterl! "1# $inute% basis "&no'n as a reportin( period% and are stored fro$ theoperational date of the cell thereb! allo'in( for past anal!sis.

). There are nu$erous counters available fro$ an RNC*RXI*RBS. +o'ever, this

procedure concentrates on counters reflectin( the critical perfor$ance of thecells. These counters "and for$ulae derived there fro$% are best anal!sed(raphicall! throu(h the use of FACTS. The for$ulae used for statistics such asCR and CSSR $a! be obtained 'ithin the FACTS.

-. Both the NC and the /lannin( 0 pti$i2ation 3n(ineer are responsible for$onitorin( counters. The NC has the responsibilit! of $aintainin( the activestatus of all cells and therefore $ust act in accordance to all such related

3G Cell Optiis!tion


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counters. The /lannin( and pti$i2ation 3n(ineer $onitors and acts oncounters reflectin( the cell4s active perfor$ance.

5. It is possible to confi(ure alar$s to be (enerated for counters e6ceedin( specificvalues. These alar$s 'ould then be $onitored b! the NC.

#. For the Radio /lannin( 0 pti$isation 3n(ineer the focus is on $aintainin(adeuate cell perfor$ance in ter$s of Accessibilit! "call setup anal!sis%,Retainabilit! "drop call anal!sis% and Inte(rit! "speech ualit!*video ualit!*pac&etthrou(hput anal!sis%

ACCESSI"ILITY

7. If a cell has poor accessibilit! it is t!picall! due to either so$e for$ of con(estionor a hard'are*soft'are fault or a $isconfi(uration. It is also possible that there is

so$e e6ternal source of interference "such as a $icro'ave lin& on the sa$efreuenc!% affectin( the accessibilit!.

8. Accessibilit! should be $onitored independentl! for the different RAB t!pes "e.(.Speech, CS 9ideo, /S Interactive R::, /S Interactive +S/A, etc.% as in certainsituations onl! one of the RAB t!pes 'ill be affected. For e6a$ple, a disabled+S;TXB 'ill affect the accessibilit! of the /S Interactive +S/A RAB, but if theRBS also has a TXB "non;+S% installed then the other RABs $a! continue tohave an acceptable accessibilit!.


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E#!ple FACTS Report sho'in( a lo' CSSR Speech caused b! a hi(hp$NoReeniedAd$. Note that p$NoReeniedAd$ is not RAB specific so otherRABs 'ill $ost li&el! be affected in this case too.

A$ission Control% DL Po&er

:. If Ad$ission Control re>ects a RAB establish$ent due to a lac& of po'er thenthe counter pNo'!ile$R!bEstAtteptL!c(DlP&ris incre$ented. Chec& thatthe feeder losses are confi(ured correctl! in the RBS and that the para$eter!#i)Tr!nsissionPo&er is set correctl! "t!picall! to$a6l/o'erCapabilit! $inus .)dB$%. The value of para$eter p&rA$shouldalso be verified "t!picall! set to 8#D%. Also, chec& for C/A alar$s i.e.so$eti$es RBS -)) sites 'ith hi(h feeder losses are confi(ured 'ith t'oC/As per sector and one of the C/As fails resultin( in a lar(e reduction in the$a6l/o'erCapabilit! of the sector and, hence, causin( a lac& of po'er.on( ter$ solutions are to increase the po'er capabilit! of the sector b! addin(or up(radin( an C/A "RBS -)-% or RE "RBS -)7%, re;en(ineerin( the site to

reduce feeder len(ths, or perhaps to chan(e the RBS t!pe to one usin( RREs"RBS -5) or RBS -51)% if this provides hi(her po'er at the reference point. Theshort ter$ solution is to reduce the traffic carried b! the site "See the ?Trafficffload@ sections%.


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E#!ple FACTS Report sho'in( a hi(h no of RAB establish$ent failures due toAd$ission Control re>ections caused b! a lac& of po'er. In this situation the site hadonl! one of the t'o C/As in sector 1 functionin( correctl! causin( the po'ercon(estion. This is sho'n in the cabinet vie'er snapshot belo' "Red 3 on C/A%.There 'as also an alar$ in the RBS for the fault! C/A.


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A$ission Control% DL C*!nnelis!tion Co$es

1. If Ad$ission Control re>ects a RAB establish$ent due to a lac& of channelisation codes then the counterp$NoFailedRab3stAtte$ptac&lChnlCode is incre$ented. This 'ill t!picall!affect the /S Interactive R:: "C+*FAC+% CSSR 'orse than the Speech CSSRas the /S Interactive R:: RAB reuires channelisation codes at a lo'erspreadin( factor "usin( $ore of the code tree%. In the /5 soft'are release a cellthat supports R:: and +S/A t!picall! has # spreadin( factor 17 channelisation codes reserved for +S/A. This $eans that appro6i$atel! -)Dof available codes are reserved for +S/A. =hen this is the case it is co$$onfor channelisation code con(estion too occur. Chec& the settin( of para$eter$lCo$eA$"t!picall! set to


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E#!ple FACTS Reports sho'in( a hi(h no of RAB establish$ent failures due toAd$ission Control re>ections caused b! a lac& of channelisation codes and thecorrespondin( decrease in CSSR for /ac&et Interactive. In this case a lar(e portion ofthe speech calls 'ere alread! redirected to GS so the R:: /ac&et Interactive RAB'as 'orst affected the reuired solution is sectorisation of the inbuildin( antenna

s!ste$ or i$ple$entation of a second carrier freuenc!.


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A$ission Control% UL+DL ASE

11. If Ad$ission Control re>ects a RAB establish$ent due to a lac& of E or airspeech euivalent "AS3% then the counterspNo'!ile$R!bEstAtteptL!c(UlAseor

pNo'!ile$R!bEstAtteptL!c(DlAseare incre$ented. The AS3 $onitoraccounts for the air interface resource usa(e in a cell "separatel! for E and %b! $eans of an avera(e static load esti$ation of each radio lin& in the cell for$ore infor$ation refer to the ?Capacit! ana(e$ent@ docu$ent in the ?=CARAN@ A3X librar!. Because a R4s AS3 is an esti$ation it is possible that incertain situations it is an over;esti$ation of the load in a cell e.(. for inbuildin(cells on a different carrier freuenc! to the surroundin( $acro cells. In suchsituations it is possible to increase the E* AS3 ad$ission control li$it"para$eters aseElAd$*aselAd$% in order to prevent unnecessar! ad$issioncontrol re>ections of RAB establish$ents. So, a short ter$ solution to relievesuch con(estion $a! be to increase aseElAd$*aselAd$, but the effect on

CR*CSSR should be closel! $onitored "Note that the aseElAd$ default valueon TN4s net'or& is alread! less strin(ent than the 3ricsson default%. Anothershort ter$ solution is to reduce the traffic carried b! the site "See the ?Trafficffload@ sections%. The lon( ter$ solution is to add another cell in the covera(earea to ta&e so$e of the traffic this $a! be achieved b! introducin( a secondcarrier, another sector, or another site.


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E#!ple FACTS Report sho'in( RAB establish$ent failures due to Ad$ission Controlre>ections caused b! a lac& of E AS3. In this case the E AS3 con(estion 'as $inorcon(estion for a fe' da!s so no action 'as ta&en.

A$ission Control% Connection Liits

1). If Ad$ission Control re>ects a RAB establish$ent due to e6ceedin( theconfi(ured connection li$it for SF usted Class B HoS settin(s on the Iub interface% in 'hichcase so$e connection li$it re>ections 'ere obtained. But this is a specialsituation and for the purpose of this docu$ent such connection li$it re>ectionsare not 'orth further consideration.


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A$ission Control% ,!r$&!re Us!-e .C*!nnel Eleents/

1-. It is possible for Ad$ission Control to re>ect a RAB establish$ent atte$pt due toinsufficient E or RBS hard'are capacit! i.e. too fe' channel ele$entsavailable. The channel ele$ent capacit! of an RBS $a! be soft'are li$ited

"accordin( the soft'are license confi(ured for the RBS% or hard'are li$ited"accordin( to the TXBs and RAXBs installed in the RBS%. T*e t&o p!r!eterst*!t control t*e R"S *!r$&!re !$ission polic0 !re )l,&A$ !n$$l,&A$1 "0 $ef!)lt t*ese p!r!eters s*o)l$ be set to 24 in &*ic*c!se no *!r$&!re is reserve$ for *!n$overs !n$ A$ission Control &ill notbloc( RA" est!blis*ent !ttepts for t*is re!son "see ?Failure After

Ad$ission +ard'are Esa(e@%. In soft'are revision P5 t*ere is no specificco)nter to in$ic!te t*is t0pe of A$ission Control rejection6 so ifpNoRe7Denie$A$ is tri--ere$ &it*o)t !n0 of t*e ot*er relev!ntco)nters in$ic!tin- ! re!son t*en it is li(el0 t*!t t*is is t*e c!)se !n$ t*!t)l,&A$ or $l,&A$ is incorrectl0 confi-)re$ to ! v!l)e belo& 24. In

the /# soft'are release there are ne' counters that indicate 'hen lac& ofhard'are capacit! causes RAB establish$ent failures in a cellp$NoFailedRab3stAtte$ptac&l+',p$NoFailedRab3stAtte$ptac&l+'Best,p$NoFailedRab3stAtte$ptac&El+',p$NoFailedRab3stAtte$ptac&El+'Best.


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E#!ple FACTS Reports sho'in( RAB establish$ent failures due to Ad$issionControl 'ith no counter sho'in( the reason "this is for /5%. In this case the +=ad$ission li$its 'ere suspected and found to be ul+'Ad$8 and dl+'Ad$8"instead of both bein( 1%. After correctin( these settin(s the Ad$ission Controlre>ections disappeared and, as can be seen in the second plot belo', the /ac&et CSSR

i$proved. In the third plot belo' the E C3 Esa(e is seen to pea& around 5# C3s. ThisRBS had a capacit! of 75 E C3s 8D of 75 C3s is 55.< C3s. In other'ords, the EC3 Esa(e and the Ad$ission Control li$it correlate to each other.


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'!il)re After A$ission% I)b Con-estion

15. If a ETRAN cell has a hi(h nu$ber of RRC*RAB establish$ent reuest failuresafter bein( ad$itted b! Ad$ission Control "p$NoFailedAfterAd$%, then aco$$on reason 'ould be due to Iub Con(estion. =hen considerin( the Iub

interface it is i$portant to re$e$ber that $ainl! RABs confi(ured to use strictAA) HoS settin(s 'ill be bloc&ed at call setup b! AA) CAC. T!picall! the R::RABs "i.e. all RABs e6cludin( +S/A and 3E RABs% are confi(ured to use

AA) HoS class A or class B, 'ith both classes confi(ured to use a strict HoS.+S/A and 3E 'ill t!picall! use AA) HoS class C and class , 'ith bothclasses confi(ured to use a best effort HoS. T!picall! the R:: /ac&et InteractiveRAB 'ill be the first RAB to sho' si(ns of AA) con(estion 'ith a poor /ac&etInteractive CSSR and correspondin( hi(h p$NoFailedAfterAd$. The AA)Setup Success Rate statistics fro$ the relevant RXI to'ards the RBS $a! thenbe investi(ated. This should t!picall! be ::D and above, but if not and thecounter pUnS)ccO)tConnsLoc!lindicates that it is local re>ections "on the

RXI% b! CAC, then there is con(estion on the Iub interface.

E#!ple FACTS Reports sho'in( hi(h p$NoFailedAfterAd$ "1stplot%, lo' CSSR/ac&et Interactive ")ndplot%, and lo' AA) Call Setup Success Rate 'ith correspondin(hi(h p$EnSuccutConnsocal "-rdplot%. Fro$ )7;11;)5 the proble$ disappears. Inthis case the solution 'as to activate irected Retr! to GS and to chan(e the AA)HoS class B traffic to use a best effort confi(uration thereb! allo'in( $ore /S75*1)


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E#!ple FACTS Reports sho'in( ho' the SF 5 E setup failures"ES3TE/FAIER3SSF5% increased rapidl! after the introduction of +S/A, and thendisappeared 'hen the E -


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Offlo!$in- Tr!ffic% Directe$ Retr0 to GS8

-#. =hen a ETRAN cell is con(estin(, for 'hatever reason, one possibilit! to

provide te$porar! "and often onl! partial% relief is to enable irected Retr! toGS on that cell. In the /5 soft'are release this is the best option ho'ever forthe /# soft'are release refer to the section ?ffloadin( Traffic Service Based+andover@ belo'. nl! speech calls $a! be re;directed to the GS net'or& andonl! one directed retr! tar(et GS cell $a! be specified "t!picall! the co;sitedcell%. It is a blind redirection so it is i$portant that the tar(et GS cell has thesa$e "or better% covera(e area as the ETRAN cell. It is also ver! i$portant toensure that the GS cell has the capacit! to handle the additional speech traffic.The redirection is tri((ered b! a trans$itted po'er threshold 'hich is notideal for situations 'here po'er is not the cause of con(estion ho'ever asuitable po'er threshold $a! be established for other for$s of cell

con(estion.

E#!ple T'o slides sho'in( an e6a$ple calculation to esti$ate the po'er thresholdto use i.e. the settin( for para$eter loadSharin(Gs$Threshold.


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E#!ple FACTS Reports sho'in( ho' the nu$ber of directed retries to GSincreased as the threshold specified b! loadSharin(Gs$Threshold 'as chan(ed to1#D, 15D, 1-D and finall! &ept on 1)D "1stplot% the correspondin( i$prove$ent toCSSR Speech and the decline in p$NoReeniedAd$ "Ad$ission Control 'asre>ectin( due to a lac& of channelisation codes% ")ndplot% the correspondin(

i$prove$ent to CSSR +S "-rd

/lot%.


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Offlo!$in- Tr!ffic% Service "!se$ ,!n$over .P?@/

-7. =ith the introduction of the /# soft'are release co$es an optional feature calledService Based +andover. Si$ilar to the irected Retr! to GS feature, ServiceBased +andover allo's Speech calls to be redirected to GS, but unli&eirected Retr! it is not a blind handover at Call Setup 'ith onl! one GS tar(etcell per ETRAN cell. Instead, the speech call is established in the -G cell and theRNC then instructs the E3 to enter co$pressed $ode and to start $easurin( theGS nei(hbours defined. An IRAT + to the best GS cell candidate that fulfilsthe GS threshold criteria "(s$Thresh-a% is then perfor$ed "unless a ti$erti$es out%. This feature can also be activated per subscriber via a serviceindicator.

DE'INITIONS

&$6C: &ssociated 6C:&&(1 &!2 &daptation (ayer type 1&S) &ir Speech );uialent&!2 &synchronous !ransfer 2odeB()R Block )rror RateC&C Call &dmission Control C) Channel )lement CN Core Network


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CSSR Call Setup Success Rate6C: 6edicated Channel *!ransport Channel+6CR 6rop Call Rate6C: 6edicated hysical Channel *hysical Channel+6( 6ownlink

G): General erformance )ent :andler:S$6SC: :i%h$Speed 6ownlink Shared Channel *!ransport Channel+:S$6SC: :i%h$Speed hysical 6ownlink Shared Channel *hysical Channel+:S$SCC: :i%h$Speed Shared Control Channel *hysical Channel+:S6& :i%h$Speed 6ownlink acket &ccessI9:< Inter$9re;uency :andoer IR&! Inter$Radio &ccess !echnolo%y Iu Interface "etween an RNC and a CN Iu" Interface "etween an RNC and an RBSIur Interface "etween two RNCs2C& 2ulti$Channel ower &mplifier *"oard in RBS 311+

2G5 2edia Gateway 2u" 2ana%ement *uality of SericeR&B Radio &ccess Bearer R&N&G Radio &ccess Network &%%re%atorR&XB Random &ccess and Receier BoardRBS Radio Base StationR( Radio (ink R(S Radio (ink Set RNC Radio Network Controller RRC Radio Resource Control R7 Radio 7nit *"oard in RBS 314+RXI roduct instance of R&N&GSC Scram"lin% CodeS9 Spreadin% 9actor S

3g cell optimisation revab

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