A Thesis for the Degree of Master Voluntary Relaying MAC Protocol for Rate Adaptive Wireless Local Area Networks

To exploit multi-rate capability as well as improve performance in wireless local area networks (WLANs), many rate adaptation mechanisms are proposed on IEEE 802.11 media access control (MAC) layer. However, they lead to performance anomaly problem due to guarantee of throughput fairness. To solve this problem, many cooperative MAC protocols were proposed that are classified into packet aggregation, grouping, and relaying schemes. As the results of comparison, we focus on the relaying mechanism which efficiently supports the multirate transmission. However, no effort has been invested to exploit the multi-rate capability for power saving mechanism. Thus, we propose a Voluntary Relaying MAC Protocol, called VRMP, to achieve both performance improvement and power saving by leveraging the multirate capability. In voluntary relaying scheme, if a node can support low rate node’s packet at higher rate and has sufficient power, after cooperatively sending data packet at higher rate, all nodes go into sleep mode as quickly as possible to reduce power consumption. Simulation and analysis results show that the VRMP outperforms the legacy mechanism in terms of throughput, transmission delay and power consumption.