An Enhanced VoIP Scheduling with Silence Suppression in IEEE 802.16e/m Systems

Thanks to silence suppression, the VoIP capacity can be improved. When the voice users are listening or thinking, the VoIP system does not need to allocate resources to them, thereby being able to accommodate more users. The main issue is how to immediately allocate resources to the user, when the user transits from the silence state to the talkspurt state. The IEEE 802.16e/m system provides two typical bandwidth request methods: unicast polling and multicast polling. The unicast-polling method can ensure the bandwidth request delay, but needs more slots for polling. Contrarily, the multicast-polling method needs fewer slots for polling, but the bandwidth request delay cannot be guaranteed. Therefore, we propose the hybrid-polling method, which combines the multicast and unicast polling. Simulation results demonstrate that by properly designing system parameters, the hybrid-polling method can achieve better tradeoff between the bandwidth request failure rate and the resources needed for polling. Moreover, the proposed hybrid-polling method can achieve comparable VoIP capacity as the multicast-polling method, with a guaranteed bandwidth request delay.