Impact of Multi-Rate VoIP on Quality of Service in IEEE 802.11e EDCA With Link Adaptation

With the deployment of IEEE 802.11 wireless LANs, there is a strong requirement to support real-time applications with stringent QoS requirements on these networks. IEEE 802.11e provides QoS mechanisms of wireless LANs in the MAC layer. IEEE 802.11 supports the link adaptation function, which allows a wireless transmitter to select an appropriate transmission rate on a frame basis according to the wireless link conditions, to improve the throughput in fluctuating wireless link conditions. However, if a lower transmission rate is selected, packet delays and losses will be increased due to the poor bandwidth availability, and as a result, the quality of real-time applications will significantly deteriorate.