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A Directional MAC Protocol with Deafness Avoidance in Ad Hoc Networks

SUMMARY This paper addresses the issue of deafness in MAC(Medium Access Control) protocols for wireless ad hoc networks using di-rectional antennas. Directional antennas are expected to provide signiﬁcantimprovements over omni-directional antennas in ad hoc networks, such ashigh spatial reuse and range extension. Recently, several MAC protocolsusing directional antennas, typically referred to as directional MAC proto-cols, have been proposed for ad hoc networks. However, directional MACprotocols inherently introduce new kinds of problems arising from directiv-ity. One major problem is deafness, caused by a lack of state information ofneighbor nodes, whether idle or busy. This paper proposes DMAC/DA (Di-rectional MAC with Deafness Avoidance) to overcome the deafness prob-lem. DMAC/DA modiﬁes the previously proposed MAC protocol, MDA(MAC protocol for Directional Antennas), to reduce the number of controlmessages and also maintain the ability to handle deafness. In DMAC/DA,WTS (Wait To Send) frames are simultaneously transmitted by the trans-mitter and the receiver after the successful exchange of directional RTS(Request To Send) and CTS (Clear To Send) to notify the on-going com-munication to potential transmitters that may experience deafness. The ex-perimental results show that DMAC/DA outperforms existing directionalMAC protocols, such as DMAC (Directional MAC) and MDA, in terms ofthroughput, control overhead and packet drop ratio under the diﬀerent val-ues of parameters such as the number of ﬂows and the number of beams.In addition, qualitative evaluation of 9 MAC protocols is presented to high-light the diﬀerence between DMAC/DA and existing MAC protocols.