Please good people may you help me. We have a problem of low CSSR as low as 80% daily.
CSSR is affected by low SDCCH Assignment Success rate, when going further i noticed that we have a high number of immediate assignments failures (due to time out).
When looking into this, collecting some log file(using Nemo)and checking the layer 3 messages it shows for just 1 channel request we get as high as 10 immediate Assignments. even in idle mode we get a lot of immediate assignments.
CSSR= random access*sdcch assignment*tch assignment
since you have done traces, could you please check what is the content of the immediate assignments ? To which Channel request do they refer ?
1 Channel request = Establishment Cause + Random Number
1 Immediate Assignment = SDCCH info +
the same Random Number as the ch req it is replying to.
when the BSC receives 1 CH REQ, it replies with only 1 Imm. Assg. So your situation is very weird !
What you see in NEMO is all the immediate assignments of the cell, those are not all targeting your MS only ! All imm assg are sent on the AGCH, which is a common channel heard by all MS.
Could you please share the exact values of the indicators:
CSSR = ?
Radom Access Failure % ?
SDCCH Assignment Failure % ?
SDCCH Congestion % ?
TCH Assignment Failure %
TCH Congestion %
SDCCH Drop %
Just to avoid any ambiguity :
Those indicators should come from your QoS tool, not from NEMO.