A Robust Deafness-Free MAC Protocol for Directional Antennas in Ad Hoc Networks

Directional antennas provide many benefits such as high gain and increased transmission range in wireless networks. However, the deafness problem in directional antennas can greatly decrease transmission efficiency. For example, a source node fails to communicate with the intended destination node if the destination node is beamforming in another direction. In this paper, a deafness-free medium access control (DF-MAC) protocol for directional antennas in ad hoc networks is proposed, which is based on a code division multiple access technique. In DF-MAC, two control codes are additionally used not only for handshaking but also for overcoming the deafness problem. The proposed DF-MAC successfully solves all the four types of the deafness problem in ad hoc networks with directional antennas. To the best of authors’ knowledge, this is the first MAC protocol that completely solves all the four types of the deafness problem. Furthermore, unlike other deafness-aware MAC protocols, the proposed DF-MAC supports mobility. Simulation results show that the proposed DF-MAC outperforms the existing deafness-aware MAC protocols in terms of network throughput and control overhead in both static and mobile environments. If the deafness problem occurs frequently, the effectiveness of DF-MAC is dramatically increased.