On Wireless Ad Hoc Networks with Directional Antennas: Efficient Collision and Deafness Avoidance Mechanisms

Wireless ad hoc networks allow anywhere, anytime network connectivity with complete lack of central control, ownership, and regulatory influence. Medium access control (MAC) in such networks poses extremely timely as well as important research and development challenges. Utilizing directional antennas in wireless ad hoc networks is anticipated to significantly improve the network performance due to the increased spatial reuse and the extended transmission range. Nevertheless, using directional antennas in wireless ad hoc networks introduces some serious challenges, the most critical of which are the deafness and hidden terminal problems. This paper thoroughly explores these problems, one of which is discovered and reported for the first time in this paper. This paper also proposes a new MAC scheme, namely, directional MAC with deafness avoidance and collision avoidance (DMAC-DACA), to address both problems. To study the performance of the proposed scheme, a complete directional communication extension to layers 1, 2, and 3 is incorporated in the ns2 simulator. The simulation results show that DMAC-DACA significantly enhances the performance and increases the network throughput. This paper also reveals that deafness has a greater impact on network performance than the hidden terminal problem.