Problems due to VS.RAB.AbnormRel.PS.RF.ULSync / Huawei 3G

[Alberto Corleone]

Hi everybody,

I am working in a 3G Huawei network. Currently I am having high PS Drop Rate, the worst counter is 'VS.RAB.AbnormRel.PS.RF.ULSync' but I do not know how to attack this problem. Do you have a procedure to check/solve this issue?

Best Regards!

[babak1349]

Hello,
In a cell there is Radio link supervisor (in E******* it is named RLS) when the UL radio link can not be decoded
for a couple of frame (NOutsyncInd) the link will be marked as out of sync and if during TRlFailure , the system can not decode some frames (NInsyncInd) the radio link will be reported as failed radio link and the RCS (Radio Connection supervisor) in the case of all Radio links (legs in active set) fail, considers drop call due to UL sync and triggers drop call and release of all resources.
This can happen:
1) in poor radio conditions
2) High UL interference
3) HW issue
4) missing neighbor
,,,,
,,,,

you need to check the value of mentioned parameters
Cheers

Hi everybody,

I am working in a 3G Huawei network. Currently I am having high PS Drop Rate, the worst counter is 'VS.RAB.AbnormRel.PS.RF.ULSync' but I do not know how to attack this problem. Do you have a procedure to check/solve this issue?

Best Regards!

[indiaco]

Good answer by babak1349,

I used to work in an OPT project with Huawei, and all of a sudden we had 4 sectors whit that counter booming, they happened to be close to a military area and these kind gentlemen were trying equipment on the 3G band.... So number 2 is a good advice.
Also, number 1 and 4, I haven't had that issue regarding hardware though.

Good luck with that.

N.

[babak1349]

hi,
When there is a missing neighbor, the power control is done only through serving cell So the UE is not controlled by missed neighbor and in this case if the UE goes far from serving cell it transmits with higher power which ould be source of interference for missed neighbors and it means higher interference

We should also consider when HSUPA is activated , the UL interference in high loaded cells will increases and sometimes optimizer allows more interference for HSUPa in order to increase the throughput while the interference might increases

Furthermore, in highly loaded cells as well, the UL interference increases (load ~ noise rise)

cheers

Good answer by babak1349,

I used to work in an OPT project with Huawei, and all of a sudden we had 4 sectors whit that counter booming, they happened to be close to a military area and these kind gentlemen were trying equipment on the 3G band.... So number 2 is a good advice.
Also, number 1 and 4, I haven't had that issue regarding hardware though.

Good luck with that.

N.

[Alberto Corleone]

Thank you very much!

Your advices were vey useful for me, today I checked neighbors list and I realized there were a couple of them missing. I added them.

Also I did IOS trace to get PRACH delay, and the result is that there are UEs trying to access the cell 20km around, those UEs are causing high UL interference also, so I applied an Electrical Downtilt.

I will be monitoring performance in this cell, I hope the problem will be solved with these actions.

Best Regards!

[babak1349]

Hi again,
for cell with huge coverage area, the radio condition could be bad in some area and cell receives UL signals with low level (in this case UE transmits with high power), the point is in this case the chance of not decoding UL signal and UL sync failure increases due to low signal which means poor radio condition, the same thing applies for indoor coverage or poorly covered area.

Cheers

Thank you very much!

Your advices were vey useful for me, today I checked neighbors list and I realized there were a couple of them missing. I added them.

Also I did IOS trace to get PRACH delay, and the result is that there are UEs trying to access the cell 20km around, those UEs are causing high UL interference also, so I applied an Electrical Downtilt.

I will be monitoring performance in this cell, I hope the problem will be solved with these actions.

Best Regards!

[Cesarsan]

Hi all,

I am having the same issue during certain periods of the day and it is affecting 3 cells from the site exactly with the same behavior and in the same time. Considering that each sector covers different areas, I think this cant be a coverage problem. Besides, I have already checked RTWP and it is Ok...

Considering that each sector has 2 carriers in this site and only the 1st carrier has this counter affected, I would say that this could not be a HW problem too...

What do you guys think that could be the problem in this case?

Thanks,
Cesar

Hi again,
for cell with huge coverage area, the radio condition could be bad in some area and cell receives UL signals with low level (in this case UE transmits with high power), the point is in this case the chance of not decoding UL signal and UL sync failure increases due to low signal which means poor radio condition, the same thing applies for indoor coverage or poorly covered area.

Cheers

[khurrambilal01]

Hardware problems normally impact both carriers (a sector with two carriers F1/F2 - Same BBU, Antenna, Feeder etc) because they share same resources....

It could be due to interference which impacts one frequency more than other, Check your Carrier startegy. might be you are pushing more traffic to one carrier or segregation like HSDPA on F1 and R99/CS on F2 etc, this can cause load difference in two carriers and hence they would have different KPIs --> Not same call drops and not same users from different areas of same cell.

[vaampeere]

Hi Alberto,You can also retune values of NINsynInd and NOUTsyncInd to resolve where you think the RL conditions are poor.It can result in good KPI's for Drop calls as it will give more samples for the RL to capture.__________________________________________________Everyday is a new beginning from dark time.