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Reply To: High SDCCH Assignment Failure

#53424
m@u
Guest

My network GSM Nortel V15.1.1 is experiencing the same extrange high SDCCH Failed Assigment Rates that appear only for some hours during the day and only at some cells.

I noticed the SDCCH Failed Assigment Rate is calculed by SDCCH Seizures/SDCCH Attempts*100%

Also comparing the counters when the cell was having problems and when it was not, I realized that the counter that measures the Expiration of the T3101 (set at 3 seconds) increased from 1 when it was OK to 707 when it was with problems. For this comparison I only selected one hour (12:00) at mid day.

On the other hand checking the notifications of the Site I found that the following alarm appeared at the BTS (cell) level:

Fault number : (1266) BLOCKAGE OF RADIO CHANNEL(S) IN FREE STATE
radAnoChln : (
transceiverId : 0
channelId : 1
subChanId : 0)
(
transceiverId : 0
channelId : 1
subChanId : 1)
(
transceiverId : 0
channelId : 1
subChanId : 3)
(
transceiverId : 0
channelId : 1
subChanId : 4)

indicating the TRX0 where the BCCH (TS0) and SDCCH/8 (TS1) are defined and subchannels of the SDCCH8 (0,1,3,4 experienced blockage).

Reading about this fault, says that the RadioResourseSupervision measures the channels on BUSY and FREE state but do not understand what is the reason yet. I’ll investigate.

Also noted that the CSSR was degraded, Network and Cell. And that the SDCCH attempts were at least doubled, but the SDCCH seizures maintained the same as when the cell was OK.

How/where did you do the trace to detect via the LAU procedure?

In my case is not due to BCCH/BCC problems.