The D-ALOHA protocol for MANETs using beamforming directional antennas

It has been proposed to upgrade the performance of medium access control (MAC) schemes through the use of directional antennas, to achieve better power and bandwidth utilization. In this paper, we present and study directional random access algorithms that form the basis for MAC schemes employed by mobile nodes that share multiple access radio channels through the use of transmitter based beamforming. We characterize and represent the network throughput performance as a product of two factors: 1) a stationary factor that represents the system throughput performance under a perfect receiver location update process, and 2) a mobility factor that embeds the user mobility and location update processes in expressing the level of throughput degradation caused due to location update errors. A Directional-ALOHA (D-ALOHA) protocol is introduced and extensive performance results based on our analytical evaluations as well as on simulations are presented. We show that the D-ALOHA protocol can significantly improve performance when the beamwidth is properly selected in accordance with the underlying user mobility level.