Directional Antenna-based Medium Access Control and Routing for AD HOC Networks: Challenges and Solutions

An area of growing interest has been to apply directional antennas to MANET protocols, which typically assumed a uniform equipment of omnidirectional antennas. In contrast to omnidirectional antennas, directional antennas have the benefits of reduced collision and extension of communication distance in a narrower range of directions. Existing work that applies directional antennas to MANET mostly focuses on MAC protocols. Besides, most of them are modifications of IEEE 802.11 DCF MAC, a popular MAC protocol typically adopted by MANET research. Nevertheless, there are many other MAC protocols, such as TDMA based MAC protocols for MANET, and it is unclear how directional antennas could be applied to them as well. Though some work applies directional antennas to addressing network layer issues, these efforts focus on location assisted route discovery and neighbor discovery of nodes outside of omnidirectional coverage range, many other issues, such as network-wide broadcast, need to be addressed. This paper reviews recent advancements in directional antenna-based medium access control and routing protocols for MANET and points out the challenges and directions for future research.