A Directional-to-Directional MAC protocol for ad-hoc networks

The use of directional antennae in ad-hoc networks has received growing attention in recent years. However, most directional MAC protocols assume interchangeable directional and omni-directional modes of operation. Such operation reduces the spatial gain and introduces the asymmetry in gain problem. In this paper, we propose a directional-to-directional (DtD) MAC protocol for ad-hoc networks that operates in directional mode exclusively. The protocol is fully distributed, does not require any synchronization, eliminates the asymmetry in gain problem and alleviates the deafness problem. To study the performance of DtD MAC, we develop an analytical model that quantifies the saturation throughput in terms of the number of antennae sectors, the packet size and number of contending nodes per channel. The analytical results are validated by simulations. We show that the DtD MAC protocol can provide significant throughput improvement in ad-hoc networks, compared to the omni-directional antennae, if the number of antennae sectors is chosen appropriately.