| Use of directional antennas in wireless networks has been widely studied in recent years. Since the Medium Access Control (MAC) protocol of the IEEE 802.11 standard is designed for the use of omnidirectional antennas, it cannot work properly when directional antennas are used. To maximize the system throughput in mobile ad hoc networks, one needs to design new MAC protocols that work well with directional antennas. In this thesis, we propose a new MAC protocol that can efficiently utilize the large throughput offered by directional antennas in ad hoc networks. The proposed MAC protocol makes use of two main modes; (i) omnidirectional mode where one antenna is used for the transmission of users' control frames, and (ii) directional mode where antenna arrays are used for the transmission of data frames. We define two separate channels, one for control information and the second for data transmission. We incorporate a simple routing protocol to deal with the out-of-range problem encountered in practical scenarios. The proposed protocol takes into consideration the effect of interference arising from the side-lobes of different stations. Using a practical ad hoc network model, we present performance comparisons with different MAC protocols (including the IEEE 802.11) where we show the large throughput gains achieved using the proposed MAC protocol. |
