Performance analysis of directional random access scheme for multiple access mobile ad-hoc wireless networks

It has been proposed to upgrade the performance of medium access control (MAC) schemes through the use of beamforming directional antennas, to achieve better power and bandwidth utilization. In this paper, we consider a shared wireless medium as employed in a mobile ad hoc wireless network. We present and analyze a random access MAC algorithm that is combined with the use of directional beamforming formed by each transmitting mobile entity. Mathematical equations are derived to characterize the throughput performance of such a directional-ALOHA (D-ALOHA) algorithm. We describe the interferences occurring at each receiving node by considering both distance based and SINR based interference models. The D-ALOHA protocol includes the establishment of a (in-band or out of band) control sub-channel that is used for the transmission of location update messages. The latter is used for allowing mobile nodes to track the location of their intended destination mobiles. We employ our derived mathematical equations, as well as carry out simulation evaluations, to present an extensive set of performance results. We characterize the throughput performance of such a beamforming based MAC protocol in terms of the system's traffic loading conditions, the selected beamwidths of the antennas at the transmitting mobiles, and the mobility levels of the nodal entities. We show that the D-ALOHA protocol can provide a significant upgrade of network performance.