Problem with CS+PS Multi RAB

[samcooldude1430]

Hi,

We have Multi RAB feature is activated in all Huawei nw.

But when we are doing PS streaming (YouTube) call and at the same time if any CS (AMR Voice) calls is received then PS streaming is paused till CS conversation is going on. After disconnecting CS call the PS streaming is resumed from the paused location.

There is no problem with PS+PS Multi RAB scenario i.e when we are doing PS streaming (YouTube) and facetime (iPhone application, real time IP video call) simultaneously there is no problem and both the applications works fine simultaneously.

Please can someone let me know for what causing this Multi RAB problem.

Thanks

[giegala]

Hi,

please check what kind of multirab you are getting. Probably you are switching to R99. In order to get highest throughput multirab should be on HSPA (at least PS part). If your rab is R99, check the spreading factor - if it is high - then bitrate for your PS part of the RAB is limited. Huawei engineers like to limit the PS throughput in order to decrease MultiRAB drop rate.

Hope this helps

[samcooldude1430]

Hi,

I dont have any throughput issue as such it only arises when CS call comes the PS is completely gone!

[giegala]

Let me explain my assumption again. When you have just normal PS call or PS+PS, then you are getting data on HSPA. But when you start CS call together with PS, then you RAB is downgraded to be R99, and extreme cases it would setup PS part of the RAB to be 8 kbps - with such setup there would be no PS services!

[samcooldude1430]

Ok, So how can I prevent this down-switching of RAB to R99 during incoming CS calls?

[giegala]

First you have to check if that is the problem - check signalling first. Here are parameters that control the setup (they are for a rather old WRAN, so you have to check your version):
SET UFRC: UlDchBeUpperLimitforAmr=D8, DlDchBeUpperLimitforAmr=D64; // sets DL PS side of CS+PS multirab RAB to 64kbps and UL PS side to 8kbps.
SET UCORRMALGOSWITCH: ReservedSwitch0=RESERVED_SWITCH_0_BIT11-1&RESERVED_SWITCH_0_BIT15-1; // requires downswitching to R99 when setting up PS+CS mrab

[samcooldude1430]

and why down switching of RAB not happening when PS-PS multi RAB scenarios?

[giegala]

I can only guess why. Key point where operators are pushing vendors is to improve CS DCR. PS DCR is not that important. When you have CS+PS multirab over HSPA, then typically CS is R99 channel and PS is over HSPA. This is considered to give higher number of call drops (partially due to UE implementation). Probably HO process is not well optimized - HSDPA uses only 1 cell and CS supports soft HO.

When there is PS+PS both of them go over HSPA - they are just multiplexed in HS-MAC layer.

[samcooldude1430]

Ok..Can you please let me know how I can check the signalling, to confirm the down switching in CS+PS multirab?

[giegala]

When PS call is started from idle mode, there would RB setup. You can see there at the very bottom of the message that HSDPA is setup - there should be list of HS-SCCH channels given to be monitored. If PS session is achieved from Cell_FACH, then message would be called RB reconfiguration - HSDPA should be configured there.
Next when CS call is setup there would be RB reconfiguration. In that messaged HSDPA part of previous rab should be removed. Also you going to see SF assigned in UL and DL. Check those values as well.

Alternatively you can see the values in TEMS/ PROBE logfile as well. There would be HSDPA windows. If there is something there during PS call and nothing during CS -> downswitch to R99 is used. Also you can see UL and DL Spreading Factor. AMR call requires SF128 in DL and SF64 in UL. Check that these values are smaller in your case.

[samcooldude1430]

Thanks bro, will check the same from log file, but can you please let me know how I check this in M2000, MML command and all?

[giegala]

Hi, I have given you MML commands in previous post. They may be out of date - so pls check documentation. This mostly applies to reserved parameters, because there is tendency to give them proper name after function get wide acceptance across networks.

[ouedraogo2d]

Hi Samcoollude
I thing it may be the problem of your script.

[sabila]

please xcheck RNC config


SET UCORRMALGOSWITCH:ReservedSWITCH0=RESERVED_SWITCH_0_BIT11-??;
SET UCORRMALGOSWITCH:ReservedSWITCH0=RESERVED_SWITCH_0_BIT15-??;

if 1--> PS restrict on DCH is ON

SET UFRC: ULDCHBEUPPERLIMITFORAMR=??;
SET UFRC: DLDCHBEUPPERLIMITFORAMR=??;

and the UFRC is to drop the bitrate till may be D8 kbps

xcheck it firts

[patek1968]

it depends which carries you are trying to do this multi-rab. If your PS started on dedicated PS carrier channel, there should be no issue with throughput as well as the voice. Because if your try to do multi-rab on dedicated CS carrier channel, you will be getting R99. Thanks

[Vladislav]

Hi,
If still actual
MML command:
SET UCORRMALGOSWITCH: MapSwitch=MAP_CSPS_PS_UL_USE_DCH_SWITCH-0,MAP_CSPS_PS_DL_USE_DCH_SWITCH-0;
In case of CS+PS Multi rab this will map PS service to HS channels in UL and DL.
AMR drop will be increased, but subscriber will not have throughput limitation during voice call.

Hope will be helpful.