- This topic has 6 replies, 1 voice, and was last updated 12 years, 10 months ago by varun sharma.
21st December 2009 at 20:46 #60451JeffGuest
What could be the reason for the following scenario:
A call in 1800 band SFH (1×3)good rxlevel(-70 to -73dBm), sqi=30, good rxqualsub but very poor FER and BER are seen on TEMS during drive test, also the called part can hear the conversation clearly but the caller part hear the “cracking voice”. No call drop, No handover failure. MAIO, HSN and MA List are Ok.
Please help.21st December 2009 at 21:40 #60452RexGuest
Just one call, how many calls? How many cells are affected?
Rex21st December 2009 at 21:42 #60453PixGuest
Please double check your values : the rxqual is directly linked to the BER. Bad BER = bad RXQUAL.
What is the RxQual_Full?
The SQI also should be taking into account the FER… So bad FER = bad SQI.
Now the thing is : we could assume that the voice is poorly encoded by the TRX, or that the called part is sending “poor” speech frames. But in this case, the BER and FER would be good in the TEMS.
There is something wrong in your DT analysis… Are you looking at instantaneous values, or do you make an average over 5 consecutive seconds
-pix22nd December 2009 at 06:28 #60454JeffGuest
Only one site is has this problem in town. Almost every call turns into cracking voice (One side). Nothing wrong with drive test analysis. I wish you could see the logs. Situation is stable (not some seconds).It’s strange.22nd December 2009 at 08:41 #60455PixGuest
Can you check if this is happening in the whole BTS, or only one cell, or only one TRX ?
I would assume a TRX is faulty, and swap it. Indeed, the TRX is the one in charge of encoding the voice, so a VQ problem is probably related to it.
Also, there is few radio mechanisms that could affect the VQ :
1. the DTX (discontinuous transmission). Try to disable this feature in this cell (DL DTX = off).
2. the TFO (if it is on, then turn it off, to test)
3. the AMR (perhaps ?) Try to turn that off too, if it was on.
But those features are usually activated on all the cells. So why would a feature not work in a particular cell ? Well, probably because the TRX is faulty…
So conclusion is still the same.
I can see the log file… if you do a screen shot of 3 consecutives measurements, showing the BER, FER, RXQUAL SUB & FULL, RXLEV SUB & FULL and SQI 🙂
You can upload those shots easily through photobucket.com. Just sen me the HTTP links.
Pix22nd December 2009 at 09:53 #60456AliAsgherGuest
In case you find the problem on all sectors + all trxs then will it be possible to provide your 1800 with another transparent E1. Believe me but the same problem in our network was resolved after providing a transparent E1. The BTS and BSCs were of Huawei.
Also how could be FER and BER poor with good SQI and RxQual. (Are you looking at FER Sub or FER Full) ?
Regards,16th January 2010 at 11:51 #60457varun sharmaGuest
I am very new in GSM technolgy.
During drive test we used to see Rx lev sub and full & Rx qual sub and full.
Which one should consider full or sub and why?
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