Fast retransmission mechanism for VoIP in IEEE 802.11e wireless LANs

IEEE 802.11 wireless LANs provide a cheap and high data rate mobile service. Voice service through wireless LANs has became an important issue. The new IEEE 802.11e standard provides a framework to support quality of service (QoS) according to traffic type. The enhanced distributed channel access (EDCA) mechanism, which is contention-based access, has several access parameters which are able to give a higher access probability to the high priority service. Since a real time service, such as voice over IP (VoIP), has a delay constraint to guarantee QoS, fast collision resolution is required. We review the IEEE 802.11e standard and propose a new fast retransmission mechanism for VoIP packets to reduce the delay and improve the channel utilization by eliminating the overhead time for backoff procedures. Simulation results show that the proposed scheme reduces the delay and dropping probability of VoIP packets.