Impact of Mobility to the VoIP over HSUPA System Level Performance

The aim of this paper is to evaluate the impact of mobility to the performance of voice over IP (VoIP) service in high speed uplink packet access (HSUPA) network. The focus in the paper is on the uplink performance of VoIP as the uplink is considered most often to limit the overall coverage. When considering user's mobility in the network, it is crucial to know how it impacts to overall performance, so that possible corrective measures can be taken. In this paper, the mobility is studied with detailed handover modeling including the effect of handover delays and active set sizes in different scenarios. The system performance is evaluated with dynamic system level tool in which mobility of users, radio resource management functionalities and the interactions between them are explicitly taken into account. The study indicated that the system performance is significantly affected by user mobility. Handover delay proved to have rather minor impact on the performance with low user velocities as performance loss remained within 10 % provided that the delay stayed within reasonable limits. Limiting the active set size was observed to reduce the VoIP capacity only slightly as long as at least two links were allowed in the active set. In addition, silence indication frames specified for VoIP caused only a slight additional performance loss in mobility scenarios.