Distributed QoS Control for Link Adaptive Wireless LANs

In wireless local area networks (WLANs), the necessity of quality-of-service (QoS) control for uplink flows is greater and greater with interactive applications being more popular. It is also important that fairness between flows transmitted by stations with different physical transmission rates is ensured in QoS control for link adaptive WLANs, which is widely used nowadays. In this paper, we propose a novel distributed access scheme to satisfy these requirements, called QC-DCA. QC-DCA adaptively controls the parameters of carrier sense multiple access with collision avoidance (CSMA/CA). QC-CDA has two QoS control functions: guarantee and classification. QC-DCA guarantees target throughputs and packet delays by quickly adjusting CSMA/CA parameters. In QoS classification, the difference of throughputs and packet delays between different QoS classes is maintained. In both of them, QC-DCA solves unfairness caused by difference of transmission rates in the physical layer. We evaluate throughput and delay performances of the proposed scheme through computer simulations. The results verify the viability of the proposed scheme.