The improvements in ad hoc routing and network performance with directional antennas

The ad hoc network has typically been applied in military and emergency environments. In the past decade, a tremendous amount of MAC protocols and routing protocols have been developed, but most of these protocols are designed for networks where devices equipped with omni-directional antennas. With fast development of the antenna technology, directional antennas have been proposed to improve routing and network performance in ad hoc networks. However, several challenges and design issues (like new hidden terminal problem, deafness problem, neighbor discovery problem and routing overhead problem) arise when applying directional antennas to ad hoc networks, consequently a great number of directional MAC and routing protocols have been proposed. In this thesis the implementation of directional antennas in ad hoc networks is studied from technical point of view. This thesis discusses the problems of utilizing directional antenna in ad hoc networks and reviews several recent proposed MAC algorithms and routing algorithms. The improvement of ad hoc routing and network performance with directional antennas compared with omni-directional antennas are evaluated based on simulations which are done with the QualNet simulator. The main finding of this study is that directional antennas always outperform omni-directional antennas in both static and mobility scenarios, and the advantage of directional antennas is more obvious when channel condition becomes worse or mobility level is larger. This thesis provides a survey of directional MAC and routing protocols in ad hoc networks. The result and principles obtained in this thesis are quite valuable for researchers working in this field. They can use it as reference for further researches. The theory parts of smart antenna technology and IEEE 802.11 MAC protocol can be considered as a technical introduction for beginners