A Distributed Asynchronous Directional-to-Directional MAC Protocol for Wireless Ad Hoc Networks

The use of directional antennas in ad hoc networks has received growing attention because of its high spatial reuse and high antenna gains. The medium access control (MAC) protocol design with directional antennas is nontrivial due to the deafness and collision problems. The existing protocols assumed that the nodes can operate in both directional and omnidirectional modes. However, using both modes leads to the asymmetry-in-gain problem. In this paper, we propose a directional-to-directional (DtD) MAC protocol, where both senders and receivers operate in a directional-only mode. We also derive the saturation throughput of ad hoc networks using DtD MAC. The analytical and simulation results show that DtD MAC can significantly improve the throughput and maintain good fairness among competing flows. We further evaluate the DtD MAC with millimeter-wave (mmWave) communication technologies, which rely on a directional antenna to perform well and can achieve gigabit data rates. The results obtained are exciting and show that DtD MAC is a promising candidate for mmWave ad hoc networks.