immediate assignment reject is caused by sdcch congestion : if no SDCCH resource is availble in the BTS, the BSC sends an immediate assignment reject.
Can you give, at the busy hour, the following QOS indicators:
1. nb of SDCCH requests
distribution of types of sdcch requests (loc upd, ms orig, ms term, sms, etc.)
2. nb of SDCCH rejected due to congestion
3. nb of SDCCH allocated
4. SDCCH erlang at busy hour
5. SDCCH capacity of the cell