EDMAC: An enhanced directional medium access control protocol for 60 GHz networks

Recent technology advances are poised to enable low-cost, low-power communications in the 7 GHz of unlicensed spectrum at 60 GHz millimeter wave (mmW) frequencies. In 60 GHz networks, transmitters and receivers employ directional antennas and point their main beams toward each other to overcome high propagation losses and achieve high data rates. However, CSMA based directional MAC (DMAC) protocols suffer from the "deafness" problem which causes unfairness and low channel utilization. This paper examines the deafness problem from a new perspective and shows that unfairness and low channel utilization are caused by the exponential backoff mechanism. We propose an enhanced DMAC (EDMAC) protocol that does not use an exponential backoff mechanism, instead employing a low control overhead protocol that enables receivers to adaptively tune senders' contention window sizes. NS-2 simulation results are given to demonstrate that EDMAC compares favorably to DMAC, achieving similar capacity and lower delay jitter in single hop networks, and significantly higher capacity in multi-hop ad hoc network scenarios.