Abstract

In a typical mobile ad hoc network (MANET), all nodes contend for a single channel access using carrier sense multiple access with collision avoidance (CSMA/CA). Thus, a fundamental limitation of MANET is that, as the number of nodes increases, the performance of the system will dramatically degrade due to the large number of collisions. This, in turn, results in an overall low system throughput. Several researchers have focused on the potential throughput gains achieved using directional antennas in ad hoc networks. When compared to omnidirectional antennas, directional antennas are more attractive option in terms of power and bandwidth efficiency. On the other hand, when used in ad hoc networks, directional MAC (DMAC) protocols usually require all nodes, or part of nodes, to be aware of their exact locations. The location information is typically provided to the DMAC protocol from upper network layers, for example, by using a Global Positioning System (GPS). Other problems that face these DMAC protocols are the deafness problem and the hidden terminal problem. Solving these problems is at the core of designing any DMAC protocol. At the same time, DMC protocols should not sacrifice channel bandwidth to deal with theses problems. In this thesis, we propose an efficient 2-channel 2-mode DMAC protocol. In particular, our protocol employs two frequency division multiplexed channels: Channel one is used for omni mode packets transmission and channel two is used for directional mode packets transmission. Estimation of Signal Parameter via Rotational Invariance Technique (ESPRIT) is used for direction of arrival (DOA) estimation. By avoiding the reliance on GPS for obtaining the position information, our protocol is also suitable for indoor environments. Under different operating conditions and channel models, our simulation results clearly show the improved throughput of our protocol compared to IEEE 802.11