The use of directional antennae in ad hoc networks can provide high spatial reuse of spectrum and antenna gains. However, employment of directional antennae poses great challenges such as hidden terminal and deafness problems. The existing directional medium access control (DMAC) protocols usually work in a switching mode of omnidirectional listening and directional sending, which, however, introduces high hardware complexity and asymmetry-in-gain. In this paper, we propose a new fully-distributed directional-to-directional MAC protocol (FDD-MAC) for mobile ad hoc networks (MANETs) where all nodes operate in the directional-only mode. A scanning scheme over the antenna sectors is designed in which random periods are scheduled for listening and sending alternatively in each sector for link establishment. Meanwhile, the burst directional ready-to-send RTS (BDRTS) frame and angle-of-arrival (AoA) caching scheme are also exploited to improve the efficiency. Extensive simulations are conducted to compare the performance of FDD-MAC and other MAC protocols, including link success probability, network throughput, and service delay. The results show that FDD-MAC is effective and efficient in solving the deafness problem in MANETs, especially with high node density and traffic load.
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