Priority-Based Opportunistic MAC Protocol in IEEE 802.11 WLANs

In wireless environments, the inherent time-varying characteristics of the channel impose great challenges on medium access control design. In recent years, multiuser diversity and opportunistic medium access control schemes have been proposed to deal with the channel variation in order to efficiently improve the network throughput. In this paper, we propose a novel MAC protocol called Priority-Based Opportunistic (PBO) Medium Access Control Protocol. It takes advantage of multiuser diversity, rate adaptation and Black-Burst (BB) contention to prioritise different users and resolve the contention for shared medium access in a distributed manner. Particularly, rather than simply measuring the channel condition for a node pair each time, with the help of multicast Request-To-Send (RTS), multiple candidate receivers with qualified channel condition are selected and prioritised. Each qualified candidate receiver then concurrently contend to send out BB, pulse of energy, the duration of which is proportional to its priority. The receiver with the best channel quality among multiple candidate receivers is always successful to send back Clear-To-Send (CTS) control packet and ultimately receives packets from the sender due to its longest BB. Extensive simulation results show that our protocol achieves much better performance than legacy IEEE 802.11 and other auto rate schemes with minimal additional overhead.