WCDMA compressed mode triggering method for IRAT handover

Inter radio access technology handover (IRAT HO) is important for WCDMA which does not have full coverage everywhere in the initial phase of its deployment. Compressed mode (CPM) is used to create gaps for IRAT (GSM) mobile measurements needed to ensure robust handover performance. CPM and IRAT HO is triggered by either common pilot channel (CPICH) Ec/Io, CPICH received signal code power (RSCP), or a combination of them. Our analysis shows that neither CPICH Ec/Io nor CPICH RSCP triggering can individually guarantee good performance for arbitrary WCDMA traffic load. The proposed combined CPICH Ec/Io and CPICH RSCP triggering oppositely exhibits sufficient robustness. The performance is quite good regardless of traffic load. Further investigations show that the combined triggering method also ensures good performance for different cell sizes and mobile speed.