Fawaz, Nadia (2008) Communications coopératives pour les réseaux ad hoc sans fil. PhD thesis Communications Mobiles, EURECOM, ENST p.186.

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Abstract

Wireless ad hoc networks received significant attention because of their defense and commercial applications. Most research on ad hoc networks focused on routing protocols. However, the theoretical and practical limits of the performance of dense ad hoc networks recently unveiled, revealed the need for alternative techniques to improve the interference-limited performance of dense ad hoc networks.

In this thesis, we address the following issue: how can the link-capacity performance in wireless ad hoc networks be improved through the use of more advanced physical layer techniques?

We first introduce the physical layer factors that impact the performance of dense ad hoc networks. In particular, we show how the throughput can be improved by using directive antennas, or by managing the number and position of relays. Then, we turn our attention to ad hoc networks in which nodes are empowered with cooperative capabilities. We first consider networks with a small number of nodes and propose techniques to improve spectral efficiency. The proposed cooperative strategies make more efficient use of the wireless resource by combining orthogonality-relaxation and dirty paper coding. Finally, networks with a high density of nodes are examined and cooperation is introduced through a cooperative-clustering approach. Using tools from random matrix and free probability theory, we analyze the asymptotic capacity of the system when the node density increases.

This thesis shows that the link-capacity performance of dense wireless ad hoc networks can be improved as long as nodes are empowered with cooperative capabilities at the physical layer, and cooperative strategies are properly designed.

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