- This topic has 5 replies, 1 voice, and was last updated 10 years, 2 months ago by homa.
25th July 2009 at 19:57 #58178ZbigniewGuest
in our network we see a lot of SDCCH & TCH Abis Failures due to “T9103 expired”. The timer T9103 (Nokia default: 2 sec) measures the time between “Channel Activation” and “Channel Activation Acknowledge” on the Abis Interface.
What could be the reason for this fault ? I think it is not related to a faulty Abis Interface because many cells show this behaviour.
Maybe the problem is related to some other timers (which ?) in higher network elements ?
Tnx in advance
Zbigniew26th July 2009 at 00:11 #58179PixGuest
in the channel activation, the BSC asks the BTS to activate a certain timeslot and associate ciphering and speech codec to it.
do you think some BTS woul have a problem applying ciphering or speech codecs required by the BSC (i’m thinking about A5/3 or AMR)
you can investigate further in this direction:
– what is the content of channel activation
– why the BTS wouldn’t acknowledge this message ? which field would be a problem ?
if you have Abis failures, it would impact not only this message, but it would generate call drops, sdcch drops, etc.2nd August 2009 at 06:58 #58180ZbigniewGuest
here is what we have found out by now.
The appropriate (Nokia) counter (1075 “SDCCH Abis Failure Call” shows high values) is not only incremented if the timer T9103 expires. We made a trace and it shows that the “Channel Activation Ack” is sent by the BTS in question. So the problem occurs in the next step: BSC sends “Immediate Assignment” but the MS can not hear the BTS anymore and it does not answer with “SABM”. So the BTS will not send “Establish Indication” to the BSC. Therefore the SDCCH connection is released and the call setup fails.
We think that there might be a problem in the link balance after implementing EDGE in these cells.
Do you have any other ideas related to this topic ?
Tnx Zbigniew2nd August 2009 at 11:38 #58181PixGuest
Well, it is a radio problem then, nothing special. Why did you write a wrong definition of the counter ?
it could be due to link balance, either on the specific trx that carries the sdcch ts, but it could be on several trx’s as well (the combiner is faluty ?)
apart from link balance, check interference and coverage problems.3rd August 2009 at 07:27 #58182ZbigniewGuest
the counter 1075 is triggered by several reasons (T3109 expiry, Immediate Assignment not answered etc.). So the definition is not wrong but it is not unique …
Zbigniew3rd February 2011 at 16:51 #58183homaGuest