What are the major differences between GSM and UMTS handover decision?

GSM:

 Time-based mobile measures of RxLev and RxQual – mobile sends measurement report every SACH period (480ms).

 BSC instructs mobile to handover based on these reports.

UMTS:

 Event-triggered reporting – UE sends a measurement report only on certain event “triggers”.

 UE plays more part in the handover decision.