Performance Improvement using Directional Antennas in Ad Hoc Networks

Novel preventive link maintenance scheme based on directional antennas has been proposed to extend the life of the link for multihop infrastructureless networks such as Mobile Ad Hoc Networks (MANET). We use the ability of directional antennas to orientate radio signals into the desired directions. We investigate preventive link maintenance scheme to on-demand routing algorithms. The scheme of creating directional link is proposed to extend the life of link that is about to break. To be more specific, preventive warning is generated to previous node in the path to create directional antenna pattern. Link is considered in danger when received packet power is close to minimum detectable power. We call orientation handoff to the process of changing the pattern of antenna from omnidirectional to the directional. We see the performance improvement at network layer by using the proposed scheme. We do a comparative performance study between omnidirectional and directional antennas for DSR (ondemand routing protocol) using simulation with OPNET. By using directional antennas, substantial gain is achieved in terms of end-to-end delay, aggregate throughput, average data packets dropped, packet delivery ratio, and routing overhead. The proposed scheme is general and can be used with any other on-demand routing algorithms.