A Directional MAC Protocol with Deafness Avoidance in Ad Hoc Networks

Abstract

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.