In normal case, the location update process is as follow:
MS -> BSS: CHANNEL REQUEST
BSS -> MS: IMMEDIATE ASSIGNMENT
MS -> BSS: LOCATION UPDATE REQUEST
BSS -> MS: LOCATION UPDATE ACCEPT
In the abnormal case, due to SDCCH congestion, the process will be:
MS -> BSS: CHANNEL REQUEST
BSS -> MS: IMMEDIATE ASSIGNMENT REJECT
In this case the location updating is not started. The IMMEDIATE ASSIGNMENT REJECT will indicate the value for the timer T3122. At the MS side, the timer T3122 will start and when this timer expires, the MS will makes another attempt for location updating.
However the total number of attempts will be limited by the “Attempt Counter”.
Brgds//