Mute call on 3G

[djordjebeg]

Hi NSN 3G experts,
since one year almost we have here and there mute call occurred.
It occurrs randomly event when radio conditions are perfect.
We run RU20 MP5 at the moment .

Do you have some experiance why it happens?
It happens for different cases - 3G AMR NB - 3G/2G AMR NB; 3G WB-3GWB, 3GWB-2GNB, 3G-Fixed.

Kind Regards,

[ChristopherAlbertini]

Hi NSN 3G experts,
since one year almost we have here and there mute call occurred.
It occurrs randomly event when radio conditions are perfect.
We run RU20 MP5 at the moment .

Do you have some experiance why it happens?
It happens for different cases - 3G AMR NB - 3G/2G AMR NB; 3G WB-3GWB, 3GWB-2GNB, 3G-Fixed.

Kind Regards,

We are exactly facing the same issue.
Our RAN is NSN and the core Ericsonn.

Can anyone help to locate where the issue is?

[djordjebeg]

We are exactly facing the same issue.
Our RAN is NSN and the core Ericsonn.

Can anyone help to locate where the issue is?

dear,

we have also E/// Core.
I asked also E/// yesterday to check if they have observed similar case somewhere else. it might happen that problem is in core.
But we I had traced one of my collegue and traces showed that UE had just lost connection for 15 seconds ( no measurement reports seen) and than cell update happenda with cause radio link failure .
Colleague had multirab and also seen RLC reset in RNC.
As a workaround to diminish negative perception ( until we solve problem completely) decrease T313 timer from 8 to 3 sec and increase T314 from 4 to 8 sec.
So the problem could be L1 radio synchronization as well.
We are confused now and NSN support is hopeless...

have you open the ticket to NSN. Mybe our and your NSN support can contact each other ?..

regards,

[ChristopherAlbertini]

dear,

we have also E/// Core.
I asked also E/// yesterday to check if they have observed similar case somewhere else. it might happen that problem is in core.
But we I had traced one of my collegue and traces showed that UE had just lost connection for 15 seconds ( no measurement reports seen) and than cell update happenda with cause radio link failure .
Colleague had multirab and also seen RLC reset in RNC.
As a workaround to diminish negative perception ( until we solve problem completely) decrease T313 timer from 8 to 3 sec and increase T314 from 4 to 8 sec.
So the problem could be L1 radio synchronization as well.
We are confused now and NSN support is hopeless...

have you open the ticket to NSN. Mybe our and your NSN support can contact each other ?..

regards,

Can you please share the results of the traces done?
Also, can you please explain what you are expecting by changing T313 and T314 timers?

[djordjebeg]

Mon_11FA_0.rarMon_11FA_0.rar

please find attached trace.
if we decrease T313 than UE will sooner start procedure searching new cell and re-establishment will eventually occur faster - so less silent experience from end user observed.
now user can see silent for N312x50 ms + T313 ~ 9 sec and than it can start with cell update ( re-establishment) .
This is not solution, just a workaround at least try.
Another ting we will do is to increase EbNo for SRB3.4( associated) from default 8 db to 10 db.

regards,

[ChristopherAlbertini]

Mon_11FA_0.rarMon_11FA_0.rar

please find attached trace.
if we decrease T313 than UE will sooner start procedure searching new cell and re-establishment will eventually occur faster - so less silent experience from end user observed.
now user can see silent for N312x50 ms + T313 ~ 9 sec and than it can start with cell update ( re-establishment) .
This is not solution, just a workaround at least try.
Another ting we will do is to increase EbNo for SRB3.4( associated) from default 8 db to 10 db.

regards,

Thanks
But I though increasing the timer could help...

Can you have a look on the attached document.

Anyway, is the situation better after decreasing the timer?

[djordjebeg]

Thanks
But I though increasing the timer could help...

Can you have a look on the attached document.

Anyway, is the situation better after decreasing the timer?

we have planned to implement changes on one RNC monday next week.
Tonight is going changes of Planned EbNo for 13.4/3.4 from 8 to 10 db as NSN recommendation according to TN159.

I will inform you about result for sure.

regards,

[djordjebeg]

yes CS drop is decreased from statistic point of view. But on the other hand you have masked problem with radio interface failure and i suggest to look to KPI relating to ratio of rl failuers and toatl established rab.

RL_FAIL_SRNC_RNL (M1005C204)/( RNC_2008a + RNC_2011a )

[djordjebeg]

or it is even better formula for soft failure ( not counted as a drop but counted as service short brake ) :

(DEL SHO SRNC ACT RL SYN FAIL/
RL SETUP SUCC FOR FIRST RL+
RL BRANCH ADD SUCC SHO SRNC+
DEL SHO SRNC ACT RL SYN FAIL)

[ninjafine]

Mon_11FA_0.rarMon_11FA_0.rar

please find attached trace.
if we decrease T313 than UE will sooner start procedure searching new cell and re-establishment will eventually occur faster - so less silent experience from end user observed.
now user can see silent for N312x50 ms + T313 ~ 9 sec and than it can start with cell update ( re-establishment) .
This is not solution, just a workaround at least try.
Another ting we will do is to increase EbNo for SRB3.4( associated) from default 8 db to 10 db.

regards,

Hi! Looking to your trace i may say that radio is almost perfect right before drop:
EcNo -4,5;
RSCP -85;
Ue Tx Power -4.

But during the call UE goes to Compressed Mode while being in MultiRAB. You may check if this RAB combination is tested good enough even for Compressed Mode
in your RAN+Core combination. You may check also if there is no alarms with NodeB synchronization.