Performance improvements to the AODV routing protocol and multiple hop wireless routes : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Engineering in Computer Systems Engineering at Massey University, Palmerston North, New Zealand

Abstract

This research focused on improving the performance of the Ad-hoc On-demand Distance Vector (AODV) routing protocol over multiple hop routes. The two specific areas that this research addressed were the dramatic decrease in throughput over multiple hop IEEE 802.11 wireless routes and the problems caused by the use of hello messages by AODV implementations to detect broken routes. To help ensure that this research was suitable for real world scenarios, only off-the-shelf software and hardware was used for both the implementations and the tests. This thesis firstly presents an overview of IEEE 802.11 based wireless networking and the AODV protocol, along with wireless networking and networking in general within the Linux operating system. The thesis then presents the problems caused by hello messages and shows how the IEEE 802.11 wireless standard contributes to the dramatic decrease in throughput over multiple hop routes. To overcome the hello message problems, an AODV implementation was developed which used existing mechanisms on the data link layer, specifically the transmit retry limit, rather then hello messages to detect broken links. To address the multiple hop route throughput problem, the use of two and four IEEE 802.11 based wireless network interfaces per node were investigated, rather than using just a single wireless interface per node. These proposed solutions, and the AODV implementation that was developed as part of this research, were then tested in the areas of functionality and throughput performance improvements. The thesis concludes by presenting the performance improvements resulting from using multiple interfaces per node and the non hello message based AODV implementation along with outlining possible future research in this area.