Deafness-Aware MAC Protocols for Ad Hoc Networks with Directional Antennas: A Comparative Study

Abstract

Directional antennas provide a great number of benefi ts such as higher gains and increased transmission ranges. They also suffer from a number of problems that also apply to omnidirectional antennas in ad hoc networks, such as hidden terminals, exposed terminals, and mobility support. But directional antennas suffer uniquely from a deafness problem, which can greatly decrease their efficiency. New medium-access control (MAC) protocols have been proposed in order to address the deafness problem. No proposal to-date completely solves the deafness problem. This paper surveys MAC protocols as related to the deafness problem in ad hoc networks with directional antennas. To the best of the authors' knowledge, this survey is the first attempt to review deafness-aware MAC protocols for ad hoc networks with directional antennas. After describing how deafness occurs, we review and discuss MAC protocols that address and partially solve the deafness problem. Then, the MAC protocols are qualitatively compared. Finally, challenges, opportunities and suggestions are discussed.