A MAC protocol for directional hidden terminal and minor lobe problems

Recently, several directional MAC (medium access control) protocols have been proposed for wireless ad hoc networks. Directional antennas have significant potentials to improve network performance. However, these directional MAC protocols also have problems which do not exist when using omni-directional antennas. One of the problems is the directional hidden terminal problem. This problem is caused by the difference of the antenna gain between the omni-directional antenna and directional antenna. In addition, a practical antenna has side and back lobes. These minor lobes have non-negligible effects on the interference in network nodes. In this paper, we propose a directional MAC protocol called DMAC-PCDR (directional MAC with power control and directional receiving) that mitigates the interference caused by directional hidden terminals and minor lobes. DMAC-PCDR has two features. First, the nodes rotate directionally receiving antenna beams in an idle state. Second, the proposed directional MAC protocol has three access modes and uses these modes depending on the location information. The simulation results show that DMAC-PCDR improves throughput performance.