What is Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA)

Directional antennas have gained immense popularity among researchers working in the area of wireless networks. These antennas help in enhancing the performance of wireless networks through increased spatial reuse, extended communication range, energy efficiency, reduced latency, and communication reliability. Traditional Medium Access Control (MAC) protocols such as IEEE 802.11 are designed based on use of omnidirectional antennas. Therefore, suitable design changes are required to exploit the benefits of directional antennas in wireless networks. Though directional antennas provide many benefits to enhance network performance, their inclusion in the network also results in certain challenges in network operation. Deafness is one such problem that occurs among nodes using directional antennas. This chapter concentrates on the problem of deafness, which is introduced due to the use of directional antennas in wireless ad-hoc, sensor, and mesh networks. Many researchers have provided numerous solutions to deal with the problem of deafness in these networks. In this chapter, the authors first explain the problem of deafness and then present an extensive survey of solutions available in the literature to deal with the problem of deafness in wireless ad-hoc, sensor, and mesh networks. The survey is accompanied by a critical analysis and comparison of available solutions. Drawbacks of available solutions are discussed and future research directions are presented.