GSM&UMTS Training Course 5-GSM CS Call Drop Problem Analysis 20111130-A-V1.0
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Transcript of GSM&UMTS Training Course 5-GSM CS Call Drop Problem Analysis 20111130-A-V1.0
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8/10/2019 GSM&UMTS Training Course 5-GSM CS Call Drop Problem Analysis 20111130-A-V1.0
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HUAWEI TECHNOLOGIES CO., LTD.
www.huawei.com
Huawei Confidential
Security Level:internal1/17/15
2011-10-26
GSM Skills Promotion CS Call Drop Prolem
!nalysis
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Content
Call Drop Counters an" Si#nalin# !nalysis $ypes o% Call Drops $imers &elate" to Call Drops Proce"ure %or Locatin# Call Drops $roules'ootin# Proce"ure Discussion
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Call Drop Counters and SignalingAnalysis
($&)0*!: Call Drop &ate on $C+ per cell,.clu"in# +an"over/ Call Drops on $rac C'annel3 . 41005,Success%ul
$C+ Sei7ures ,$rac C'annel/3 8 9umer o% Success%ul ncomin# nternal nter-Cell +an"overs3 8Success%ul ncomin# .ternal nter-Cell +an"overs3 - 9umer o% Success%ul ;ut#oin# nternal nter-Cell+an"overs3 - Success%ul ;ut#oin# .ternal nter-Cell +an"overs3/
($&)0*: Call Drop &ate on $C+ per cell,inclu"in# +an"over/ Call Drops on $rac C'annel3 < 41005,Success%ul
$C+ Sei7ures ,Si#nalin# C'annel/3 8 Success%ul $C+ Sei7ures ,$rac C'annel/3 8 Success%ul $C+ Sei7uresin $C+ 'an"overs ,$rac C'annel/3/
Call Drop &ate on $C+ per cell,.clu"in# +an"over/ in"icates t'e call "rop rate in t'e stale state= >it'
re#ar" to t'e %ormulas %or calculatin# t'e t?o counters@ t'e numerators in ot' %ormulas are t'e same@
e.cept t'at Success%ul $C+ Sei7ures in $C+ 'an"overs ,$rac C'annel/ is inclu"e" in t'e "enominator o%
($&)0*:Call Drop &ate on $C+ per cell,inclu"in# +an"over/ ut not in t'e "enominator o% ($&)0*!:Call Drop
&ate on $C+ per cell,.clu"in# +an"over/= $'ere%ore@ t'e value o% t'e %ormer is smaller t'an t'at o% t'e
latter=
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Types of Call Drops
1 CMC!Call Drops on "adio #nterface $Tra%c Channel& indicates call drops due to poor 'm interface (uality) which isthe most common cause of call drops on a networ*. CM!Call Drops due to A+is Terrestrial ,in* -ailure $Tra%cChannel& and CM!Call Drops due to (uipment -ailure $Tra%c Channel& indicate call drops due to transmissionand e(uipment faults) respecti0ely. ay attention to these two counters if their 0alues are large.
2 #n the sta+le state) focus on CM33!Call Drops on Tra%c Channel in Sta+le State $rror #ndication& and CM31!Call
Drops on Tra%c Channel in Sta+le State $Connection -ailure&. 4enerally) call drops in the sta+le state as indicated +yCM31!Call Drops on Tra%c Channel in Sta+le State $Connection -ailure& account for the largest proportion of calldrops due to poor 'm interface (uality.
#n the hando0er state) focus on 127Ca!6um+er of 'nsuccessful utgoing #nternal #nter8Cell ando0ers $Timer9pired& $TC-& $Tra%c Channel& and 12:Ca!6um+er of 'nsuccessful utgoing #nternal #nter8Cell ando0ers$Timer 9pired& $TC& $Tra%c Channel& +ecause inter8cell hando0ers account for a large proportion.
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Timers "elated to Call DropsMSC $imers
$)0A $)06 $)0B $))B
The MSC uses the timers T35) T3;) and T: to monitor on8hoo* procedures. T3: is used to monitor the
resource release procedure. All of these timers must +e set during
message +efore the timer e9pires) the MSC clears the call. #f this timer is set to too large a 0alue) the
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Timers "elated to Call Drops$)01
This timer speci=es the period during which a phone is ringing. The MSC starts this timer upon recei0ing an
Alerting message and stops it upon recei0ing a Connect or Disconnect message. #f this timer e9pires +efore the
MSC recei0es either message) the MSC sends the calling MS a Disconnect message containing the cause 0alue?1@ user alerting) no answer) instructing the calling MS to clear the current call. #n addition) the MSC sends the
called MS a Disconnect message) containing the cause 0alue ?132 reco0ery on timer e9piry or cause 0alue
?1 normal) unspeci=ed) instructing the called MS to clear the current call. #f this timer is set to too large a
0alue) the
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Timers "elated to Call Drops ESC $imers
$)10) Series
ando0er completion message timers consist of T13A) T13C) and T:. #f any of these timers is set to a
small 0alue) the
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rocedure for ,ocating Call Drops
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rocedure for ,ocating Call Drops
Page !
Call Drops on m nter%ace in t'e Stale State
Bhen a call is in the sta+le state) call drops may occur after a
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rocedure for ,ocating Call Drops Call Drops on m nter%ace in t'e +an"over State This type of call drop occurs after a
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rocedure for ,ocating Call Drops Drops Due to 9o Measurement &eport Sumitte" y t'e MS This type of call drop seldom occurs. #f a large num+er of call drops occur +ecause the
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Trou+leshooting rocedure Scenario 1 $roules'ootin# Call Drops Due to $ransmission aultsSymptom 14enerally) A+is interface transmission faults may lead to an increase in the 0alue of CM!Call
Drops due to A+is Terrestrial ,in* -ailure $Tra%c Channel&) and the Ater/A interface transmission faultsmay lead to an increase in the 0alue of CM!Call Drops due to (uipment -ailure $Tra%c Channel&.
2 A+is/Ater/A transmission lin* insta+ility may increase the call drop rate. Chec* the rele0antalarms to determine the lin* transmission status.
Possile Causes The rele0ant
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Trou+leshooting rocedure Scenario 2 $roules'ootin# Call Drops Due to Huipment aults
Symptom 1 n the
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Trou+leshooting rocedure Scenario ) $roules'ootin# Call Drops Due to Poor m nter%aceKuality
Symptom 1. Chec* #nterference
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Trou+leshooting rocedure Scenario * $roules'ootin# Call Drops Due to Poor Covera#e
Symptom
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Trou+leshooting rocedure
Proce"ure
1. AdFust the networ* parameters to optimiHe hando0er relationship and hando0er speed. 2.
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Trou+leshooting rocedure Scenario A $roules'ootin# Call Drops Due to Poor m nter%aceKuality
Symptom
The call drop rate increases signi=cantly if MSC8 or
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Trou+leshooting rocedure 9ei#'orin# &elations'ip #f only some neigh+oring cells are con=gured in the
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Trou+leshooting rocedureProce"ure
1. Iiew the tra%c statistics and operation logs to chec* whether the call drop ratesigni=cantly increases when an MSC cuto0er is performed or when the relatedparameters are modi=ed on the MSC or the
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DiscussionSymptom
Cell < con=gured with T"L7 and cell C con=gured with T":L11 were in thesame
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Discussion
Symptom
There are two
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