In case on SDCCH congestion , Is there a repetition of channel request?Only in case of location update and call reestablishment allowed?
The KPI SDCCH_congestion rate is thus wrong because it contains redunduncy?
if the sdcch is congested, the BSS will behave accordingly to your setting “Enable Immediate Assignment Reject”.
If “ImmAssRej” = DISABLE then the MS will repeat the Channel Request almost immediately
If “ImmAssRej” = ENABLE then the MS will repeat the Channel Request only “WI_xx” ms later, which provides more chance for a SDCCH channel to be available.
The MS can send up to MAX_RETRANS+1 channel requests.
Yes, the SDCCH Congestion is artificially increased by retransmission. However, if you activate the “ImmAssRej”, you can apply the formula:
SDCCH_Cong – Imm_Ass_Rej / Channel_Request
As a result, you are counting only the last congestion failure. If the SDCCH is setup at the 3rd attempt :
SDCCH Cong = 3
Imm Ass Rej = 3
–> sdcch cong rate = 0%
I hope it makes sense… please test the formula carefully because I don’t remember having tried it.
(i didn’t care much about artificial SDCCH congestion.. it should always be zero IMO… really and artificially !)