Performance Evaluation of HSDPA Mobility for Voice Over IP

In this paper we evaluate the performance of the serving HS-DSCH cell change procedure for delay sensitive services, like voice over IP (VoIP). The impact of the signaling procedure delay on the user plane performance is studied by means of dynamic system simulations. The simulation results show that within the studied range, the duration of the signaling procedure starts to impact performance only for terminals moving 50 km/h, or faster. Parameter tuning and combining the procedures for active set update and change of best HS cell can considerably improve the performance, so that even at 120 km/h, less than 2% of the handovers suffer interruptions longer than 100 ms. Thus, the HSDPA handover procedure in Rel-6 can be made fast enough to accommodate VoIP users traveling at 120 km/h with acceptable conversation quality.