The past decade has witnessed a remarkable interest in wireless ad hoc networks that operate without any infrastructure support. The potential for deployment of such networks exists in many scenarios ranging from civil and construction engineering, and disaster relief to sensor networks and military applications. The IEEE 802.11 Distributed Coordination Function (DCF) is the dominant MAC protocol for wireless ad hoc network. However, the DCF method could not utilize shared channel efficiently and suffers from various problems such as exposed and hidden terminal problems. Therefore, in recent years, various methods have been developed to address these problems and accordingly increase the overall network throughput, which mainly involves adjusting the carrier sensing threshold, replacing the ornnidirectional antennas by directional antennas and controlling packet transmission power adequately. Directional antennas offer numerous advantages over ornnidirectional antennas and thus could enhance the performance of ad hoc networks. They focus energy only in the target direction and offer longer transmission and reception ranges for the same amount of power. This feature could be used to adjust the power of the transmitter when a directional antenna is in use. Sorne power controlled directional MAC protocols have been proposed in the literature. Most of these proposais consider only directional transmission and, in their simulation studies, they usually assume the communication range of ornni and directional antennas are the same. Apparently this assumption is not supported in any realistic situation. Moreover, there is a lack ofwork that considers the heterogeneity in ad hoc networks. In this thesis, we propose a suitable power controlled MAC protocol for ad hoc network with directional antennas by taking ail of these issues into consideration.
