Enhancing QoS of voice over WLANs

Voice over IP (VoIP) service is emerging as a popular application in wireless local area networks (WLANs). However, the existing rate adaptation (or link adaptation) schemes for WLANs have been developed to improve the throughput of data traffic, not the quality of service (QoS) of VoIP traffic. In this paper, we investigate the characteristics of VoIP traffic and the limitations of state-of-the-art rate adaptation schemes, and then enhance the QoS of voice over WLANs (VoWLANs) by ameliorating the existing rate adaptation schemes. Specifically, we design fast decrease to control the transmission rate of retransmissions, and retry scheduling to avoid the deep fading of the wireless channel as well as hidden terminal interference. We comparatively evaluate the QoS of the revised rate adaptation schemes via ns-3 simulations and MadWiFi implementations in various communication environments, and demonstrate that the proposed scheme improves the R-score performance by up to 80% depending on the network scenarios.