QOAR: Adaptive QoS Scheme in Multi-Rate Wireless LANs

With the availability of multiple rates in IEEE 802.11 a/b/g wireless LANs, it is desirable to improve the network capacity and temporal fairness by sending multiple consecutive frames over high rate links, as proposed in opportunistic auto rate (OAR [1]). However, the basic OAR does not provide quality of service (QoS) guarantee and thus is not sufficient in supporting real time voice/video traffic. In this paper, we further enhance the OAR protocol with a set of QoS mechanisms. The proposed QOAR protocol consists of two protocols: (i) a traffic- differentiating flow weight adaptation protocol (FWA) that dynamically tunes both contention window and concatenation number per channel access; (ii) an admission control protocol (AC) that guarantees the bandwidth/delay requirements of multimedia services. Extensive simulation studies show that QOAR enables QoS for real-time traffic yet maximizes performance of best effort traffic.