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triple-x
2010-01-16, 06:32 AM
Dear All,

I have observed bad BLER (>20%) from the drive test logs in condition good receive level (>-75 dBm) and also good C/I (>15dB). It's Huawei EGSM network, what could be the reasons?

Cheers.

mirza
2010-01-17, 04:41 PM
Dear All,

I have observed bad BLER (>20%) from the drive test logs in condition good receive level (>-75 dBm) and also good C/I (>15dB). It's Huawei EGSM network, what could be the reasons?

Cheers.

Hello

Not sure for Egsm network but for UMTS i would recommend to check the pilot pollution

Thanks

Mirza

mp9413
2010-01-17, 04:47 PM
If you are using TEMS to do the drive test, check the C/I of each carrier, it could by one of the carrier in poor RF condition. Retune and test again.

asifhaider919
2010-01-17, 04:52 PM
Dear All,

I have observed bad BLER (>20%) from the drive test logs in condition good receive level (>-75 dBm) and also good C/I (>15dB). It's Huawei EGSM network, what could be the reasons?

Cheers.

Well this condition could be due to the 'frame slips' caused at the transmission end. Check the transmission alarms on that particular site.

RF engineer
2010-01-17, 04:52 PM
the site which connect to BSC port may be not working check with bsc eng to change the site to other port and do test again

mp9413
2010-01-17, 04:57 PM
Well this condition could be due to the 'frame slips' caused at the transmission end. Check the transmission alarms on that particular site.

If "frame slips" is the cause, the sudden dropped call statistics should be higher than usual statistics. Agree?

asifhaider919
2010-01-17, 05:04 PM
If "frame slips" is the cause, the sudden dropped call statistics should be higher than usual statistics. Agree?

yes ofcourse the statistics of dropped call would be higher in that case and would be pegged as RF drops because the RLT would expire due to the BLER being high and SACCH unable to decode.

triple-x
2010-01-18, 07:23 PM
Dear All,

I have observed bad BLER (>20%) from the drive test logs in condition good receive level (>-75 dBm) and also good C/I (>15dB). It's Huawei EGSM network, what could be the reasons?

Cheers.

Thanks for your inputs.
Let me be more specific. The drive test was carried out using Huawei Genex Probe, bad BLER happened in some parts of the driven route whereas others are good. Please take a look at below snaps and let me know your opinion and suggestion, thanks.

http://i739.photobucket.com/albums/xx34/ajaxboy99/RxLevplot.png

http://i739.photobucket.com/albums/xx34/ajaxboy99/CIplot.png

http://i739.photobucket.com/albums/xx34/ajaxboy99/BLERplot.png

mp9413
2010-01-20, 12:06 AM
Hi,
It is difficult to tell as we are not working with the network. However, I think you can carry out a step by step elimination approach:

First you have to identify if it is a hardware/software problem or RF problem

Hardware/Software:
1. asifhaider919 and "RF Engineer" have suggested some hints, you can check it first

2. Check the statistics of the problem cell as well. If it has high dropped call or high intracell handover, it should have problem.

3.If statistics is poor, reload software, block TRX to see if problem can be sovled or not.

Once hardware/software can be confirmed, then it should be RF problem, the most straight forward way is retune.

Rgds,
MP

Lucky
2010-02-07, 05:35 PM
Thanks for your inputs.
Let me be more specific. The drive test was carried out using Huawei Genex Probe, bad BLER happened in some parts of the driven route whereas others are good. Please take a look at below snaps and let me know your opinion and suggestion, thanks.

http://i739.photobucket.com/albums/xx34/ajaxboy99/RxLevplot.png

http://i739.photobucket.com/albums/xx34/ajaxboy99/CIplot.png

http://i739.photobucket.com/albums/xx34/ajaxboy99/BLERplot.png

I would suggest to check the UE used. If you have more than one UE then it's easy as you can compare. Sometime the UEs specially samsungs do that.

recpich
2010-04-16, 03:20 AM
Hi ,i suggest you to check transmission part..


BR

da_manole
2010-04-16, 06:01 AM
Hello

Not sure for Egsm network but for UMTS i would recommend to check the pilot pollution

Thanks

Mirza

if c/I it's good no pilot polution

kamy
2010-04-16, 12:02 PM
if c/I it's good no pilot polution
okie, i agree with you. I suggest that you should check the hardware of BTS if UL BLER is not good, and also for DL BLER (check the test phones)

da_manole
2010-04-16, 03:23 PM
the Bler is high only in some small areas or everywhere? If is just in some small area we can check correlated interference (same scrambling cod received from other BTS) else if we are facing with this problem on all area served by one BTS we should try to check the power control