An Opportunistic Directional MAC Protocol for Multihop Wireless Networks with Switched Beam Directional Antennas

Directional antennas in multihop wireless networks offer a potential increase in the spatial reuse of the wireless channel. However, existing directional MAC protocols are not capable of fully exploiting this essential benefit. In this paper, we propose OPDMAC which is an opportunistic directional MAC protocol that is motivated by the possibility of achieving higher spatial reuse. The proposed protocol is novel in its backoff mechanism with directional antennas. If a node is forced to backoff due to a missing CTS or acknowledgement in one direction, OPDMAC explores transmission opportunity in other directions. This minimizes the idle wait time of the wireless channel and increase the channel utilization. In addition, OPDMAC is found to decrease the effect of deafness without additional control overhead. Our simulation results show that OPDMAC outperforms existing directional MAC protocols in terms of throughput, delay and fairness.