Persistent packet scheduling performance for Voice-over-IP in evolved UTRAN downlink

In this paper we present and analyze different packet scheduling mechanisms for Voice-over-IP (VoIP) in UTRAN Long Term Evolution Downlink. Dynamic packet scheduling provides multi-user and frequency domain scheduling gain, but at the expence of high control channel utilization. VoIP service with high number of simultaneous users and small packets can cause the control channel consumption to be the bottleneck for VoIP performance. Thus several persistent packet scheduling mechanisms have been proposed in 3GPP, such as fully persistent, talk-spurt based persistent and semi-persistent packet scheduling. We analyze the VoIP performance of different packet scheduling mechanisms by using fully dynamic system level simulations. We observe that with dynamic packet scheduling the VoIP capacity is restricted by the control channel capacity, whereas with persistent scheduling the capacity is restricted by the delay budget due to worse PRB SINR and resulting increased number of retransmissions.