Directional monitoring MAC protocol using smart antennas in wireless multi-hop networks

Recently, many studies in wireless ad hoc networks assume the use of smart antennas which can electronically control their beam pattern. Communications using smart antennas can be expected to improve spatial utilization efficiency and to extend communication distance. However, there are some unique problems caused by the use of the smart antennas. In this paper, we focus on the directional hidden terminal and the deafness problems. We propose a directional monitoring scheme and a switching backoff scheme for overcoming these problems. The directional monitoring scheme can solve the directional hidden terminal problem by monitoring the direction toward the destination after sending a data packet. The switching backoff scheme can reduce deafness loss time by keeping backoff-interval as long as the terminal is deaf. Comparing the proposed scheme with conventional schemes by computer simulations, the results show that the proposed scheme can mitigate the effect of these problems and it achieves higher throughput.