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I have found blocked call(SD block) in TEMS log file.
The layer 3 message was ‘missing immediate assignment’ while the MS requested channel(AGCH) (in the call attempt retry).
After 2 retry (as by the max_retransmission parameter)the call was blocked.and the layer 3 message was ‘No immediate assignment’.
What does that layer 3 messages mean?Does it mean to any specific cause for that Block?
I know that thats a SD block.But I couldnt find the reason for that block.There supposed to be no SD blocking.why there was no immediate assignment command from the bts after ms requested for channel by RACH?..what may be the cause?..
This is normal,
In case the SDCCH channels are all busy (= high sdcch congestion rate), then the BTS doesn’t have to reply to the MS.
The MS will then retry by itself, by sending a second and then a third CHANNEL REQUEST.This is a standard mode of operation.
There is feature called “immediate assignment reject” that can be activated, so the BTS will send a message (IMMEDIATE ASSIGNMENT REJECT). This is not mandatory though. It works better this way though (generates less sdcch congestion), so I usually recommend to activate it.
hi Pix,
Other then SD Congestion,is there any other reason which may cause bts doesnt have to reply to ms?
Because,I found no SD congestion for that cell fom the statistics.“There is feature called “immediate assignment reject” that can be activated, so the BTS will send a message (IMMEDIATE ASSIGNMENT REJECT).”
thats mean we have to enable this feature to get “immediate assignment reject” in case of SD congestion?hi,
other possibility: the BTS never received the channel request in the first place. A problem of poor path balance (problem of UL reception), or just bad coverage ?
Or interference on the UL BCCH?for the 2nd question: yes
Hi, Pix.
If the MS request is filtered using RACH_TA_FILTER is there any specific message via air interface?
BR
TNS,
No DL message at all.
The MS will retry MAX_RETRANS times to send a CH_REQUEST but there’ll never be an answer from the BTS.Yes, I know it…
So it’s another possibility (for answer of the main case )…BR
Oh, ok, i got it now. the question mark threw me off the scent 🙂
HI, Pix
I was almost sure, so it was a question.
After you confirmation it was a “conclusion”.
(I know it = I knew it – my mystake ).BR
We are getting to a serious degree of subtlety here… 🙂
immediate assignment
the missing immediate assignment would definetely mean there was no sd allocated.This could be due to more reasons other than blocked SD.simply put,an sd assignment failure.could be due to a lack of sd resources,radio issues,TX issues between BSC and BTS…etc
how many call attempt retry is possible before call block?
