Thank you Pix, for your response.
I don’t Know what happens for foreign MS. Notice that a new roaming agreement was made with a foreign operator few days before the trouble. But I’m not sure that MS from this operator roam in the concerned area(it’s a new operator and this border area is far from the main towns).
The site is a S112 and the problem is more serious for the one TRX sectors. For them there is no need to set a priority they carry the sdcch.
I give you some statistics, that could help for further analysis. The comparison is made between two date, before and after the problem.
Random access attempt:
369257 vs 441223
Random access success:
23,17 vs 58,2 (increase during the problem)
SDCCH:
seizure attempts:85623 vs 255732
congestion(%):0.16 vs 26.33
time congestion(%):0.03 vs 7.03
success at seizure(%):81.58vs55.02
drop(%): 6.17 vs 45.77
mean holding time:6.29s vs 11.15s
LOCATION UPDATE:
attempts:80800 vs 247715
success(%): 83.99 vs 33.38
The site is located on a remote BSC and is not at my location, so I’m not able to make abis traces and drive test, but if the cause cannot be find without I’ll go there.
Thanks