Cooperative routing in wireless networks

Abstract

In this thesis, we study the problem of energy efficiency and reliability in wireless ad-hoc networks. First, we introduce the idea of wireless cooperation advantage. We formulate the problem of finding the minimum energy cooperative route for a wireless network under idealized channel and receiver models. Fundamental to the understanding of the routing problem is the understanding of the optimal power allocation for a single message transmission between two sets of nodes. We present the solution to this problem, and use that as the basis for solving the minimum energy cooperative routing problem. We analytically obtain the energy savings in regular line and regular grid networks. We propose heuristics for selecting the cooperative route in random networks and give simulation results confirming significant energy savings achieved through cooperation. In the second part, we study the problem of route reliability in a multi-hop network. We look at the reliability issue at the link level and extend those result to a wireless network setting. In the network setting, we first define and analyze the reliability for a fixed route and then propose algorithms for finding the optimal route between a source-destination pair of nodes. The relationship between the route reliability and consumed power is studied. The idea of route diversity is introduced as a way to improve the reliability by taking advantage of the broadcast property, the independence of fading state between different pairs of nodes, and space diversity created by multiple intermediate relay nodes along the route. We give analytical results on improvements due to route diversity in some simple network topologies.