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Hi,
We are using Ericsson equipment and encountered with the problem that MS do not response to Immediate assignment and also not send SABM message to MSC. This problem directly reflects on SDCCH establishment rate (sdcch fails due T3101 expire) and we have many customers complains due accessibility. CCCH, SDCCH resources do not perceive any congestion, interference, BSIC conflicts, signal levels in MS -75dBm.
Any ideas?Make RACH Access Level Min. to -109 and check
Now is -110. Does it make a difference?
1.) Whats the timer value for T3101. If it is greater then 3secs then it is fine.
2.) Any uplink interference (check IB report).
3.) Replace the hardware if there is no issue on the Um and Abis interface.
T3101 – 4 sec.
ICM measurements – no uplink interference;
With hardware – maybe, but observed in whole network.
The interesting thing, that in Air-interface trace(did recording with NEMO) shows, that phone replies to paging with RACH, and from the network receives Immediate assignment, and later nothing. Network repages, – the procedure repeats, but stops in the same place – no answer to immediate assignment. Isn’t clear why phone do not try to choose SDCCHHi Krishka,
How to check for the value of T3101 In Ericsson? also how to change the actual value? I do not find any command to check for.
Thanks in advance.
We did it by the requesting to ericsson, because the timer value cannot be changed by some command. But actually we didn’t see any significant improvement – huge number of sdcch fault due timer expire. The mobile do not answer to immediate assignment.
Changing T3101 will not help
Change Rach Busy threshold to 5
Change RACH Error Threshold to 200Hi Bijou, where should be defined such thresholds and what impact they can do for immediate assignment? From my point of view – there are no problems with RACH establishment – BSC responds to RACH and sends immediate assignment but MS do not configure and send SABM message on SDCCH. Did you have problems similar like that?
ThanksI do not find such parameters in Ericsson Cell describtion…
Hi kryshka
What is the value of Tx-integer in your system.Increase it & checkTx integer is 32. Previously it was 20, but the changes didn’t have results. If looking to rach establishment statistics – it’s really normally – more that 99%.
Actually,this is a normal Rf phenomenon.That is the reason we have this Max. no. of retransmission parameter to safegaurd immediate assignment.Since RACH is slotted aloha,there will be huge losses inevidently
We have MAXRET=4 in one BSC, and MAXRET=7 in second. No big difference. So, my though is something strong in the MS side, – he get all that he want from network side – channel assignment in immediate assignment message. If MS do not understand that message, – he replies with immd.ass. reject, or waits for second time. In our case, he waits 4 times and later – nothing. Why he do not react to imme.assignmt…
Hi Kryshka.
MS doesn’t give imm assignment reject.It is send by BSC under 3 conditions:
1.no available channel
2.channel activation failure
3.channel activation timeout
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