gsm&umts training course 5-gsm cs call drop problem analysis 20111130-a-v1.0

8/10/2019 GSM&UMTS Training Course 5-GSM CS Call Drop Problem Analysis 20111130-A-V1.0

1/23

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


2/23

HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential

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

Page 2


3/23


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=


4/23


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.


5/23


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


6/23


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


7/23


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


8/23


rocedure for ,ocating Call Drops

Page


9/23


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


10/23


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


11/23


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


12/23


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


13/23


Trou+leshooting rocedure Scenario 2 $roules'ootin# Call Drops Due to Huipment aults

Symptom 1 n the


14/23


Trou+leshooting rocedure Scenario ) $roules'ootin# Call Drops Due to Poor m nter%aceKuality

Symptom 1. Chec* #nterference


15/23


Trou+leshooting rocedure Scenario * $roules'ootin# Call Drops Due to Poor Covera#e

Symptom


16/23


Trou+leshooting rocedure

Proce"ure

1. AdFust the networ* parameters to optimiHe hando0er relationship and hando0er speed. 2.


17/23


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


18/23


19/23


Trou+leshooting rocedure 9ei#'orin# &elations'ip #f only some neigh+oring cells are con=gured in the


20/23


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


21/23


DiscussionSymptom

Cell < con=gured with T"L7 and cell C con=gured with T":L11 were in thesame


22/23


Discussion

Symptom

There are two


23/23

Thank youwww.huawei.com

gsm&umts training course 5-gsm cs call drop problem analysis 20111130-a-v1.0

Documents