A MAC protocol with directional antennas for deafness avoidance in ad hoc networks

Directional antennas are expected to provide significant improvements over omni-directional antennas in wireless ad hoc networks. Directional MAC protocols, however, introduce new kinds of problems arising from directivity. One major problem is deafness, caused by a lack of state information from neighbor nodes (i.e., idle or busy). This paper proposes DMAC/DA (Directional MAC with Deafness Avoidance) to overcome the deafness problem. In DMAC/DA, WTS (Wait To Send) frames are transmitted by the transmitter and the receiver after the successful exchange of directional RTS (Request To Send) and CTS (Clear To Send) to notify the on-going communication to potential transmitters that may experience deafness. Furthermore, DMAC/DA is enhanced by the next packet notification to distinguish transmitters from neighbors. We evaluate our protocol through extensive simulation study with different values of parameters such as the number of flows, data size and beamwidth. The experimental results show that DMAC/DA outperforms existing directional MAC protocols, such as DMAC (Directional MAC) and MDA (MAC protocol for Directional Antennas), in terms of throughput, RTS failure ratio, and control overhead.