Technical Issues and Challenges involve in designing a MAC protocol for Wireless Ad hoc Network

Wireless Ad hoc Networks have received significant attention in recent years due to their easiness to setup and their potential applications in many domains. Such networks can be useful in situations where there is not enough time or resource to configure a wired network. The shared media used by wireless networks, grant exclusive rights for a node to transmit a packet. Access to this media is controlled by the Media Access Control (MAC) protocol. These protocols are of significant importance since the wireless communication channel is inherently prone to errors and unique problems such as the hidden-terminal problem, the exposed-terminal problem, deafness and signal fading effects etc. Although lots of researcher has been performed research on these MAC protocols and presented various issues involved in it. Through this paper an attempt is done to present all relevant challenges/issues that may occur while designing a MAC protocol. A classification of MAC protocols and their brief description, based on their operating principles with different antenna modes and important features are discussed in this paper. Traditional MAC protocols in ad hoc networks employ omni-directional antennas. Recently, directional antennas have emerged as an alternative due to their capability of spatial reuse, low probability of detection, robustness to jamming, and other beneficial features which increases coverage range and subsequently network capacity in the communication network. Different antenna modes with their functionality and working technology are discussed. Finally, a comparison study of both omni-directional and directional MAC protocols based on their characteristics and underlying features is presented and conclude the paper. KeywordsMAC, antenna, channel, RTS/CTS, hidden & exposed terminal