the switch for this is in URRCTRLSWITCH : RSVDBIT1_BIT22
(SRB_RESET_RL_SETUP_SWITCH) , RSVDBIT1_BIT23 ( UL_RLFAIL_RL_SETUP_SWITCH) , RSVDBIT1_BIT24 ( CS Re-establishment Switch ) , RSVDBIT1_BIT25 ( PS Re-establishment Switch ) ,
RSVDBIT1_BIT26 ( UE_SRB_RESET_RL_SETUP_SWITCH) and RSVDBIT1_BIT28 ( CS_RL_RESTORE_Timer_SWITCH ) By using this parameter set and some more we can reduce the
CS and PS drop to a large extent , also attached is the DOC for the same.
Call Re-establishment feature in WCDMA
By using call reestablishment feature in the WCDMA we can reduce the
call drop in CS and PS domain. This feature enables us to successful
reestablish the call after the abnormal release indication has been sent
by the RNC.
In this doc study we will cover the below details:
1. Impact of Call Reestablishment on Network in NBH ,DBH and cell
BBH Hour.
2. Detailed parameter description and impact analysis of call
reestablishment.
3. UE Signaling analysis for CS and PS domain.
4. Further scope of improvement.
1.1 Impact of Call Reestablishment on Network in NBH ,DBH and cell BBH
By using call reestablishment feature in the WCDMA we can reduce the call drop in CS and PS domain. This feature enables us to successful reestablish the call after the abnormal release indication has been sent by the RNC.
The re-establishment procedure allows MS to resume a connection in progress after a radio link failure, possibly in a new cell or in a new location area (re-establishment in a new location area initiates no location updating).
Below trend provides the details of CSV Drop (NBH) , HS+PS Drop (DBH) and Erlang Minutes per drop (NBH) : Improvement observed in the CSV Drop and Erlang Minutes per drop.
The below trend provide the details of improvement observed in the cell BBH for the KPI CSV call drop rate and HS+PS Drop Rate.
0 100 200 300 400 500 600 700 800 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 E r l a n g m i n d r o p D r o p r a t e
CSV Drop Rate(NBH) HS+PS Drop Rate(DBH) Erlang Minutes per Drop(NBH)
Low Traffic due to Diwali Holidays
Parameter changes implemented in Jaipur RNC
Parameter changes implemented in Ajmer and
This drop rate improvement has been observed n the cell BBH level and indicates that the cell KPI has improved overall as far as the CSV and PS drop rate is considered. Beside no major impact seen on other KPIs due to this parameter changes.
On the trial basis the parameter changes were firstly performed in the Jaipur RNC on 22nd Nov 2012 and
in Ajmer and Jodhpur RNC the changes were implemented on 27th Nov 2012.
2.1 Detailed parameter description and impact analysis of call re-establishment
76 78 80 82 84 86 88 90 92 94 96 98 % o f c e l l m e e t i n g c r i t e r i a Axis Title
CSV Drop Rate 2% HS+PS Drop Rate 2%
Parameter changes done in Ajmer and Jodhpur RNC Parameter changes done
The CS call drop analysis is as shown below the basic counter responsible for the call drops are as mentioned : 1. VS.RAB.AbnormRel.CS.IuAAL2 2. VS.RAB.AbnormRel.CS.OLC 3. VS.RAB.AbnormRel.CS.OM 4. VS.RAB.AbnormRel.CS.Preempt 5. VS.RAB.AbnormRel.CS.RF 6. VS.RAB.AbnormRel.CS.RF.SRBReset 7. VS.RAB.AbnormRel.CS.RF.ULSync 8. VS.RAB.AbnormRel.CS.RF.UuNoReply 9. VS.RAB.AbnormRel.CS.UTRANgen
From the above counter list the major pegged counters are the point no. 5 , 6 and 7.
The below graph indicates the RAB abnormal release analysis for the major pegged counters in the CS domain , it can clearly be seen that the CS Call drop rate due to SRB reset and UL sync has dipped a large volume thus impacting the overall CS call drop rate :
0 5000 10000 15000 20000 25000 30000 35000 40000 45000 50000 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 R A B N o r m a l r e l e a s e D r o p R a t e
The below graph indicates the RAB abnormal release analysis for the major pegged counters in the PS domain , it can clearly be seen that the PS Call drop rate due to SRB reset , TRB Reset and UL sync has dipped a large volume thus impacting the overall CS call drop rate :
0 50 100 150 200 250 300 350 1-N o v-12 2-N o v-12 3-N o v-12 4-N o v-12 5-N o v-12 6-N o v-12 7-N o v-12 8-N o v-12 9-N o v-12 10 -N o v-12 11 -N o v-12 12 -N o v-12 13 -N o v-12 14 -N o v-12 15 -N o v-12 16 -N ov -12 17 -N o v-12 18 -N o v-12 19 -N o v-12 20 -N o v-12 21 -N o v-12 22 -N o v-12 23 -N o v-12 24 -N o v-12 25 -N o v-12 26 -N o v-12 27 -N o v-12 28 -N o v-12 29 -N o v-12 30 -N o v-12
3.1 UE Signaling analysis for CS and PS domain
The below signaling details indicate the 20 pre and post signaling at call drop , The CS Timer setted to 15000 ms for Enhanced Call Reestablishment, start after RNC send the RL Active CMD, stop after RNC receives cell update message.
0 1000 2000 3000 4000 5000 6000 0 200 400 600 800 1000 1200 1400 1600 P S c a l l d r o p O t h e r P S c a l l d r o p VS.RAB.AbnormRel.PS.RF.SRBReset VS.RAB.AbnormRel.PS.RF.ULSync VS.RAB.AbnormRel.PS.RF.TRBReset VS.Call.Drop.PS.Other
3.1.1 CS Domain call signaling :
3.2.1
The below signaling details indicate the 20 pre and post signaling at call drop , The PS Timer setted to 30000 ms for Enhanced Call Reestablishment, start after RNC send the RL Active CMD, stop after RNC receives cell update message.
PS Domain call signaling :
3.2.3
The call re-establishment details are transmitted in the SIB 4 and SIB 12 after the release indication has been received a counter N313 starts which repeats it self for the times T313 value is assigned.
We need to increases these timers in order to provide UE the time for re-laching and making a call re attempt for the RAB new connection.
In this section we will discuss the relevant further analysis and modification needed for the CS and PS call drop rate improvement
1. Further modification of counters and timers to improve the call drop rate.
2. These changes were made on the RNC level and cell level further changes need to be performed on the cell level for the in synsc and out sync parameters.
3. RSVDBIT1_BIT27 testing to be done at RNC level , in this part we need to check the pre and post changes after the RSVDBIT1_BIT27 enable and disable
5.1 Suggestions required.
Request readers for further suggestions and proposals for making further improvement in the KPIs.