Providing statistical QoS guarantee for voice over IP in the IEEE 802.11 wireless LANs

Recent years have seen greatly increasing interests in voice over IP in wireless LANs, in which the IEEE 802.11 distributed coordination function protocol or enhanced DCF protocol is used. However, since both DCF and EDCF are contention-based medium access control protocols, it is difficult for them to support the strict QoS requirement for VoIP. Therefore, in this article we propose a novel call admission control scheme that runs at the MAC layer to support VoIP services. The call admission control mechanism regulates voice traffic to efficiently coordinate medium contention among voice sources. The rate control mechanism regulates non-voice traffic to control its impact on the performance of voice traffic. Extensive simulations demonstrate that the proposed schemes can well support statistical QoS guarantees for voice traffic and maintain stable high throughput for non-voice traffic at the same time.