Analysis of UMTS IRAT Ho Issuev2

8/15/2019 Analysis of UMTS IRAT Ho Issuev2

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GSM-BSC 网上问题处理进展内部公开

Analysis of Increase in PS IRAT handover failures in

“M” city RNC for operator A.

Issue date：2013/04/19 Resolution date: 2013/07/31

1 Issue Analysis

1.1 Issue Brief desri!tion

PS IRAT HO success rate dipped from 93% around to 75% around for “M” cit R!" for

operator A

1.2 "ddition infor#ation

#、 R!" $ersion：RA! 9&&R&#'(!)"&&SPH5**

*、 Operator A is +a$in, 3) Hua-ei and *) -it+ ot+er $endor

3、 Operator A is +a$in, intra "irc.e roamin,/I"R -it+ Operator I and Operator 0

Issue Analysis pro!ress

*&1Apr1*&#32 PS IRAT of “M” cit dipped from 93% around to 75% around 4e +a$e

snc+ronied -it+ a.. t+e teams for t+e operations done on t+at da !o o6$ious c.ear c.ue

-as seen T+en -e ana.ed top ce..s and arran,ed 8M test2 and found out to,et+er -it+

*) (!OR team t+at :TS snc+roniation fai.ure -as comin, -+en t+e ;( snc+ronied

-it+ *) after ce.. c+an,e order command from 3) side And durin, t+is period2 -e to,et+er

-it+ *) (!OR team +a$e done fe- ma<or e=periments >

1, 2G VENDOR reset 2 BSC’s(MLRBSC2 and MLRBSC3) on 29th Jne, no

!"#ro$e"ent o%ser$ed&

2,2G VENDOR "!'rated RNC ro" SGSN1 to SGSN2 on 9th J*& +S R-. d!d not

!"#ro$e&

3& .o !soate R/ reated !sse 2D threshod 0as han'ed or a ster o es on 1th

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*& No !"#ro$e"ent seen&

4& On 15th J* re$erted %a6 RNC47 %a6 to SGSN1& R-. !"#ro$ed to 85

7& 2G VENDOR "!'rated one s!te ro" one #oor R-. BSC(MLRBSC3) to another

#oor R-. BSC(+.RBSC1) on 28th J*, no !"#ro$e"ent ond&

:& 2G VENDOR "!'rated one s!te ro" one #oor R-. BSC(+.RBSC1) to another

'ood R-. BSC(;<RBSC1) on 25th J*, 'ood +S R-. !"#ro$e"ent "on!tored, %t

!t d!d not ssta!n&

8& RNC reset 0as done on 3th *, no !"#ro$e"ent seen&

5& 2G VENDOR han'ed the o6 sore o one BSC(MLRRBSC) ro" =M> !t* to

=B> !t* on 31st J* -t 7 -M &<e ha$e o#ened MS %ased ?O s0!th on the sa"e da*

arond 12@ -M& -nd +S R-. !s !"#ro$!n' to 97 a%o$e ater 12 -M on0ard&

?rom a6o$e tests and e=periments2 -e suspected IMSI 6ased +ando$er s-itc+ is critica. in

t+is issue And -e started to ana.e t+e I"R re.ated impact and possi6.e reasons

" Issue #etailed Analysis

# “Ho- t+e fai.ure increases”

i 4+en -e found out t+e PS IRAT Issue2 -e audit t+e R!" operator .o, and

confi,ure pre and post2 no c+an,e found -+ic+ can affect t+e PS IRAT @PI dip in

*&1Apr

ii Team ,ot feed6ac from Operator AB3)B*) (!OR2 no c+an,e

iii Tr to understand -+ PS IRAT ?ai.ure1After T2 -e found out t+ere is

snc+roniation pro6.em -+en t+e ;( tr to access *) ce.. Cater -e did <oint dri$e

-it+ *) (!OR team2 D t+e a.so found t+e same issue

i$ So -e suspected t+e issue in c.oc 4e p.anned to mi,rate t+e *) site2 from MCR

:S" to anot+er :S" -it+ 6etter statistics ?ound t+at t+e PS IRAT impro$ed for

t+at *) site So -e -ere eroin, in on t+e c.oc

$ Mean-+i.e2 -e found out 3)1*) IRAT pro6.em for Operator I in “H” cit

R!"/anot+er R!"02 as t+e S!A" is not correct After acti$atin, t+e settin,s2 t+e





pro6.em t+e "S IRAT pro6.em ,ot reso.$ed To cross c+ec2 on 3#1Eu.1*&#32 -e

acti$ated S!A" at “M” cit R!" a.so2 -+ere t+e settin, -as not t+ere pre$ious.

T+en -e found out t+e PS IRAT @PI impro$ed

$i Tr to understand -+ t+e PS IRAT @PI issue reso.$ed2 6ase on ca.. +istor record2

-e found out 6efore c+an,e2 t+e Operator I users contri6uted t+e most PS IRAT

fai.ures And after c+an,e2 Operator I usersF PS IRAT attempt reduced from G93 to

#*2 -+ic+ means R!" succeeded in 6.ocin, OP(RATOR I PS IRAT

$ii And -e a.so ana.sed t+e Operator I users PS RA: speed2-e found out a.most 75%

of Operator I PS RA: speed is .ess t+an 3'6s2 as defau.t settin,2 R!" did not

restrict t+e PS IRAT +ando$er if t+e PS RA: speed is .ess t+an 3'6ps So -e

confi,ured R!" for IRAT settin, for different operators2 R!" a$oid t+e Operator I

usersF PS IRAT2 so t+e @PI 6ecame norma.

$iii ?rom a6o$e2 -e ,ot to no- t+e root cause of PS IRAT issue In order to confirm

a,ain2 -e c+eced -it+ t+e ca.. records of anot+er da and found t+at t+e resu.ts

-ere simi.ar In Operator 2 9'% of su6s are +a$in, M:R ,reater t+an * M:PS

Hence t+e impact -as not seen on Operator su6scri6ers





i= At t+is time2 from Operator I usersF num6er trend2 -e found out2 in *&1Apr2 t+ere

-ere around #&&& more users -+ic+ ,ot 3) acti$ate in “M” cit Operator A ;MTS

net-or

So -e ,ot t+e reason -+ t+e PS IRAT dipped :ecause in R!"2 defau.t it do not

a..o- t+e PS IRAT if t+e PS RA: speed is .ess t+an 3'6ps2 mean-+i.e2 t+e R!"

did not confi,ure t+e IRAT settin, for different operator So -+en t+e Operator I

users num6er increasin, and a.so most of t+e PS RA: speed is .ess t+an 3'6ps2

t+e PS IRAT fai.ure -ou.d increase more ?rom 6e.o- .ist -e can understand2 t+e

most of t+e PS IRAT fai.ures are caused 6 Operator I users>





* “4+o sas !o for t+ese attempts”

?rom a6o$e ana.sis2 -e see t+e IRAT fai.ures are increasin, sudden. in t+e Apri. *& t+ -it+

no operation done :ut one uestion is -+o sas no to t+ese attempts R!" is not main, ri,+t

settin,s2 PS IRATs +appen for I"R T+e S)S! +as settin,s of 6.ocin, t+ese attempts And -e

mae one comp.ete c+ec of current S)S! settin,s2 6e.o- is t+e status>

"ore settin,s of Re<ect status in t+e S)S! # D S)S! *>

*) :S" mappin, ta6.e -it+ S)S! status>

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$ Conclusion%

!o !( operation +as 6een done in a.. t+e parties2 e=cept t+e OP(RATOR I +as con$erted .o-

profi.in, user to t+e sstem2 for -+ic+ in our current sstem settin,s2 more IRATs +ad 6een

tri,,ered2 and in t+e PS core side2 -e +a$e 6.oced t+e ot+er operator users access for *)2

-+ic+ points out t+at t+e PS IRAT fai.ures -ere +i,+ for OP(RATOR I I"R users2 -+ic+

dra,,ed do-n t+e -+o.e PS IRAT success rate

T+ese fai.ures2 t+at PS IRAT fai.ure2 -i.. not affect t+e user e=perience2 for PS IRAT is not

ena6.ed an+o- for I"R partners

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& Su!!estion ' Reco((endation%

Pa"o settin,s are *

nd

.aer 6.ocin, for t+e user access2 6ut for t+e RA! side2 -e need to

+a$e ri,+t settin,s to a$oid -ron, PS IRAT attempts/# st .aer0 In “M” cit2 IMSI 6ased +ando$er

s-itc+ +as 6een put -ron,. /As &02 and -e +a$e 6.oced t+e PS IRAT for RA: -it+ more t+an

3'6ps2 and operator I users increased on Apri. *&t+ -it+ .o- profi.in, /most. #*6ps02 t+en

more OP(RATOR I PS IRATs comes2 and at core side2 -e +a$e 6.oced t+is2 so more fai.ures

appear In future2 -e need to stren,t+en RA! side to a$oid -ron, +ando$ers2 and in "ore side2 -e

need to continuous. update t+e 6.ocin, ta6.e for t+e i..e,a. users So from #st and *nd .aer -i..

6ot+ ensure t+at a.. t+e ser$ice are +appenin, ri,+t.


Documents

Analysis of UMTS IRAT Ho Issuev2