call failure troubleshooting

Upon completion this course, you will be able to:
Deeply understand MOC, MTC call flow
Deeply understand Assignment
Deeply understand Paging
Chapter 1 AssignmentChapter 1 Assignment
Chapter 2 MOC TroubleshootingChapter 2 MOC Troubleshooting
Chapter 3Chapter 3 Paging

BSC/RNC MSC
Intra MSC call MS to MS:(SRI Procedure ith !"R#
Inter MSC call MS to MS: (SRI Procedure ith !"R and

MOC – Assignment failure
A'ter sending the Assignment Request message% the MSC receives the
Assignment Response message ith the 'ailure cause value
Possible Causes
)hen this 'ault occurs% *ou need to start per'ormance measurement and
inter'ace message trace to anal*+e and locate the 'ault cause
&he cause o' the 'ault ma* ,e one o' the 'olloing: Radio channel resources are insu''icient on the BSC side &he status o' circuits on the BSC side is inconsistent ith that on the
MSC side &he A-inter'ace circuits are insu''icient &he speech versions on the MSC side are inconsistent ith those on
the BSC side
HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confdential
.uring earl* or late assignment% the local MSC receives an ASSINM0N&
1AI"$R0 message 'rom the originating BSC/RNC
2 Chec3 )hether the Success Rate o' Assignment Is &oo "o
4 Chec3 )hether &ra''ic Is &oo !eav*
5 Chec3 )hether the Num,er o' Cause 6alues Is &oo "arge
7 Chec3 )hether Radio Channels Are Insu''icient
8 Chec3 )hether the Status o' Circuits on the RAN Side Is Inconsistent )ith
&hat on the MSC Side
9 Chec3 )hether A/Iu-Inter'ace Circuits Are Insu''icient
Chec3 )hether the Speech 6ersions on the MSC Side Are Inconsistent )ith
&hose on the RAN Side
The general troubleshooting proe!ure is as follows"

MOC – Assignment timeout
Symptom
A'ter the MSC Server sends the Assignment Request message% the assignment duration
e;ceeds 5< seconds Run #ST T$M%& to chec3 hether Timer 'ame is
T'(&A)(*A$T(+O&(ASS$,'M%'T(AC-
Possible Causes
)hen this 'ault occurs% *ou need to ena,le per'ormance measurement and message trace

MOC – Assignment timeout
7 Chec3 the Status o' the M&P/M5$A Route
8 Chec3 the Status o' the M&P/M5$A "in3
9 Chec3 the Status o' the M)
Chec3 )hether the transmission Are Normal

.uring the call setup process% a'ter sending to the caller a Call PR=C00.IN% the
MSC assigns a tra''ic channel to the caller ,e'ore the callee is alerted
)SC.A MSC /#& 0#&)SC.)
CM(S%&/$C%(&%3 Proess Aess
&e4uest
S%T6P

&he MSC assigns a tra''ic channel a'ter receiving a CA"" C=N1IRM0. 'rom the
callee
Page &esponse

In the call setup process% a'ter sending to the caller a Call PR=C00.IN% the MSC
assigns a tra''ic channel to the caller a'ter the callee is alerted
)SC.A MSC /#& 0#&)SC.)
Page &esponse

&he MSC in'orms the callee o' late assignment through the S0&$P message &he
callee responds ith an A"0R&IN immediatel* a'ter the CA"" C=N1IRM0. &he
MSC assigns a tra''ic channel 'or the callee "ate assignment usuall* occurs a'ter the
MSC receives the C=NN0C& message 'rom the callee
)SC.A MSC /#& 0#&)SC.)
Page &esponse

BSC MSC
&he MSC server sends a .ISC=NN0C&
message instructing a mo,ile terminal to
disconnect a call onl* a'ter the MSC server
receives an assignment response 'rom the
access netor3

RNC MSC
time ith assignment 'ailure
Bit 22 o' P2<<9 and ,it > o' P2<<8
determines hether to ena,le the
suspension o' call disconnection a'ter
sending the assignment request and
,e'ore receiving the assignment response
Change )it 11 of P1<<= >< an! bit ? of
P1<<@ ><

'G A$$i&n(ent Succ )ate in *+S- )S)H+I
RNC-.ate
Assignmen t 1ailure due to Invalid RABI.(tim es#
Assignmen t 1ailure due to Ma;imum Bit Rate $navaila,ili t*(times#
Assignmen t 1ailure due to =ther Reasons(ti mes#
Assignmen t 1ailure due to Release o' MSC/RNC .uring Assignmen t(times#
Non- speci'ied 1ailure Cause(time s#
Success'ul &ra''ic Channel Assignmen ts(times#
&ra''ic Channel Assignmen t Requests(ti mes#
Assignmen t Succ rate
RSR!MI2-<9/<8 < < 44 4778 9<2 58<>7 585>52 ??25>>8
RSR!MI2-</<8 4 < 49 4884 8 5988<9 59>95> ??28<5?
RSR!MI2-<>/<8 2 < 44 474 849 587259 5825 ??28?2
RSR!MI2-<?/<8 2 < 4 489> 942 584822 588<2 ??2<52>
RSR!MI2-2</<8 2 < 2? 44?8 5?9 5549<7 5584?9 ??2?25
RSR!MI2-22/<8 2 < 54 2>58 484 4>??4 4>2<>4 ??48977
RSR!MI2-24/<8 2 < 45 287< 25? 4292 42?4? ??455?4
RSR!MI2-25/<8 4 < 4? 454> 598 584488 587?82 ??47<79
RSR!MI2-27/<8 2 < 2> 47?5 54< 582>5 5878?? ??4<8>9
RSR!MI2-28/<8 < < 45 4885 79> 58?598 5945>> ??298>2
RSR!MI2-29/<8 < < 4> 4757 82> 5847? 58877> ??29?>
RSR!MI2-2/<8 < < 4 484? 925 58927 58?>8> ??24954


Symptom
Possible Causes
)hen this 'ault occurs% *ou need to start user message trace &he cause o' the
'ault ma* ,e one o' the 'olloing:
2&he calling o''ice does not send the Send Routing In'ormation message to the
!"R
4&he called o''ice does not send the Providing Roaming Num,er message to the
!"R
5=ther device is 'ault* (ta3e the case that the MSC and the !"R are connected
,* the S&P as an e;ample#

2 6ie the &race =utput to Chec3 )hether the
MAP@S0N.@R=$&IN@IN1=RMA&I=N@R0 Message Is Present
4 Chec3 SCCP& Con'iguration
5 Chec3 the & o' the Called MSIS.N
7 Chec3 )hether the .SPs o' the !"R to )hich the Callee Belongs Are
Accessi,le
8 Chec3 )hether the SCCP Su,s*stem o' the !"R to )hich the Callee
Belongs Runs Normall*
9 Chec3 )hether the Called =''ice Sends the PR=6I.0@R=AMIN@N$MB0R
Message to the !"R

MOC – Call failure at the aller si!e
2 6ie the &race =utput to Chec3 )hether the
MAP@S0N.@R=$&IN@IN1=RMA&I=N@R0 Message Is Present
4 Chec3 SCCP& Con'iguration
5 Chec3 the & o' the Called MSIS.N
7 Chec3 )hether the .SPs o' the !"R to )hich the Callee Belongs Are
Accessi,le
8 Chec3 )hether the SCCP Su,s*stem o' the !"R to )hich the Callee
Belongs Runs Normall*
9 Chec3 )hether the Called =''ice Sends the PR=6I.0@R=AMIN@N$MB0R
Message to the !"R

Symptom
Possible Causes
&he cause o' the 'ault ma* ,e one o' the 'olloing:
&he call connection procedure 'ails
Supplementar* services are not su,scri,ed
Bearer capa,ilities are not supported
&he num,er anal*sis procedure 'ails
&he outgoing routing procedure 'ails

2 Chec3 hether the MSC receives the CM Service Request message% Setup
4 Chec3 hether the Bearer Service Not Implemented cause value is carried in
the Release Complete message
5 Chec3 the Setup message to see i' information transfer apability o' the
SM Bearer Capa,ilit* in'ormation element is = 7#ine28
7 Chec3 hether the reueste! faility not subsribe! cause value is carried
in the .isconnect message (C"IR Invocation in'ormation element is carried in
the Setup message#
Chec3 Authentication procedure
> Chec3 Assignment procedure

Case 1" C#$& ser9ie
&he calling S0&$P message carries the clir invocation I0% !uaei MSC queries the
6"R 'or hether the su,scri,er has su,scri,ed to the C"IR service I' the
su,scri,er does not su,scri,e to the C"IR service% the s*stem 'or,ids the call
connection through a so'tare parameter &here'ore% the su,scri,er cannot serve
as a caller
Bit 5 o' P82 determines hether to release a call hen a su,scri,er ho does not
su,scri,e to the C"IR service requires the C"IR service
6alues and .escriptions:
&he de'ault value is 2
Register the C"IR service on the !"R 'or the su,scri,er

Case 2" Call 'rom line 4 'ail
Bit 22 o' P24 determines hether the MSC supports "ine 4
D <: not to support "ine 4 I' a user calls through "ine 4% the MSC receives the call
through "ine 2
D 2: to support "ine 4 I' a user calls through "ine 4% the MSC receives the call through
"ine 4 as long as the user signs ith "ine 4 =therise% the MSC ill terminate "ine
4

MOC . Outgoing all failure
Possible Causes
2&he calling-part*s-categor* in'ormation element carried in the IAM message
does not compl* ith the requirements
4&he peer o''ice does not support the continuit* chec3
5&he attri,ute or 'ormat o' called-part*-num,er or calling-part*-num,er
in'ormation element carried in the IAM message does not compl* ith the
requirements
7&he user-service-in'ormation in'ormation element carried in the IAM message
does not compl* ith the requirements

2 Anal*+e Cause 6alues in the R0" Message
4 Chec3 )hether the IAM Message Is Normal Chec3 hether the value o' alling.partys.ategory complies ith the
carrierEs requirements Chec3 hether ontinuity.he5.in!iator is ontinuity.he5.reuire!
718 in the IAM message Chec3 hether nature.of.a!!ress.in!iator o' the called-part*-num,er or
calling-part*-num,er in'ormation element in the IAM message complies ith
the carrierEs requirements Chec3 hether the 'ormat o' a!!ress.signal o' the called-part*-num,er or
calling-part*-num,er in'ormation element in the IAM message complies ith
the carrierEs requirements Chec3 hether the user-service-in'ormation in'ormation element carried in
the IAM message complies ith the carrierEs requirements Chec3 hether the location-num,er in'ormation element is carried in the IAM
message

Chec3 hether ontinuity.he5.in!iator is ontinuity.he5.reuire! 718 in the
IAM message
Chec3 hether the peer o''ice supports the continuit* chec3 ,ecause the continuit*
chec3 is initiated 'or this call
Run MO ';T, to modi'* the value o' Continuity Che5 to 'o 'or the peer o''ice
M=. N&: CC D F0SG

Chec3 hether the 'ormat o' a!!ress.signal o' the called-part*-num,er or calling-
part*-num,er in'ormation element in the IAM message complies ith the carrierEs
requirements
Change su''i;ed ,* H1H at the calling num,er or called num,er according to a carrierEs
requirement
Run MO O+C to modi'* the su''i; rule 'or the corresponding o''ice direction
according to the carrierEs requirements

BSC/RNC MSC
Paging procedure
MTC – Paging +ailure
Possible Causes
2&he communication ,eteen the MSC and the BSC is a,normal
4&he BSC is a,normall* stopped or does not respond
5&he MSC is con'igured rongl*
7&he MSC cannot o,tain the cell data o' the su,scri,er 'rom the 6"R
8&he location area/cell (service area# con'iguration on the core netor3 side is
di''erent 'rom that on the access netor3 side

2 &race $ser Inter'ace Messages% chec3 the trace output to see i' the Paging
message is present
4 Chec3 )hether the "ocation Area .ata o' the Su,scri,er Is Present in the 6"R
5 Chec3 )hether the "ocation Area/Cell .ata on the MSC Side Is Consistent )ith
&hat on the BSC Side
7 Chec3 the Message .ispatch Capa,ilities o' the Modules on the MS=1&J5<<<
(#ST SPA Ser9ie ispath Ability is )SSAP or &A''AP8
8 Chec3 )hether the BSC Sends the .isconnect or Release Message
9 Chec3 )hether the MSC Sends the .isconnect or Release Message Be'ore
Receiving the Page Response Message
Chec3 the Status o' signaling Connected to the BSC/RNC
> uer* the paging duration #ST P,CT&#
? Chec3 the duration o' implicit IMSI detach #ST /#&C+,

A'ter the implicit IMSI detach timer times out% the 6"R automaticall* sets the
su,scri,er to the detached state
&he MSC ill not paging the $0 implicit detached ,* MSC% it ill reduce the no
response times But the pro,lem is at the same time to improve the paging success
rate% the $0 state K&he user is sitch o''L ill ,e increase
So suggest set the MSC implicit detach timer 22 times to 24 times as BSC &5424 I'
the BSC &5424 is less than 5< min% so the MSC implicit detach timer set 4 times and
8 minG i' the BSC &5424 is more than 5< min% e set MSC implicit detach timer 2
times and 8-2< min as BSC &5424
IMSI implicit detach timer in 6"R
0;plicit IMSI detach: An MS initiates the IMSI detach 'lo hen the su,scri,er poers

P299 BI&28 controls hether to measure the PAIN R0SP message hen a call is
released ,e'ore ringing I' open% the MSC ill measure the PAIN R0SP hen the
call is released ,e'ore ringing% include the M&C PAIN R0SP% PAIN R0SP
during "ocation update% 'irst paging R0SP as 'irst paging resp
Call is released ,e'ore ringing

P22<<BI&2 Controls hether to ma3e the location area update and paging at the
same time% 'or improving the paging success rate I' the location update 'ail or during
the location update process the $0 send a K'ollo onL message% paging 'ail Set
P22<<BI&2 as <% the MSC server ill send the paging message a'ter the $0 'inish
the location update

MTC – Call +ailure at the alle! si!e
Symptom
A call connection or processing 'ailure occurs at the callee side
Possible Causes
2A paging 'ails
4&he Setup message contains in'ormation elements not supported ,* the MS
5An assignment 'ails

2Chec3 hether the paging procedure is success'ul
4Chec3 hether the MS sends the Call Con'irmed message
5Chec3 hether the assignment procedure is success'ul on the callee side
7Chec3 hether the callee is alerted
8Chec3 hether the callee ansers the call

Che5 whether the MS sen!s the Call Confirme! messageB
Chec3 hether the !"C in'ormation element is carried in the Setup message%
Set ,it o' P29> to <
Bit determines hether to include the !igh "a*er Compati,ilit* (!"C# cell in
the S0&$P message hen the !"C cell e;ists
D <: not to include the !igh "a*er Compati,ilit* (!"C# cell in the S0&$P
message
D 2: to include the !igh "a*er Compati,ilit* (!"C# cell in the S0&$P message
&he de'ault value is 1

The MSC sen!s the isonnet message after the MS sen!s
the Call Confirme! message Chec3 hether the .isconnect message contains an* o' the 'olloing cause
values: no ,earer capa,ilit* availa,le this time (8>#: ,earer capa,ilit* not permit (8#: In normal cases% the ,earer service is not
provided during call aiting &he handling procedure is complete

call failure troubleshooting

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