Prix EPFL de doctorats 2011 - Özgür Aydin Ayfer

"Pour la caractérisation du comportement à grande échelle de la capacité des réseaux sans fil auto-organisés, et la conception de nouveaux schémas de communication qui approchent cette capacité."

Fundamental limits and optimal operation in large wireless networks.

The current communication architectures of wireless networks are fundamentally limited by interference between simultaneous transmissions. This interference limitation leads to poor performance in large networks, where there are typically many source-destination pairs willing to communicate simultaneously: as the number of users in a wireless network increases, the communication rate for each pair rapidly decreases. This makes current communication architectures unsuitable for large scale networks.

In this thesis, we show that this interference barrier can be surpassed with a combination of physical layer and architectural ideas. We present a new communication architecture for wireless networks which provides scalable performance. In this new architecture, nodes cooperate so as to constructively use interference for communication. As a result, the rate for each source-destination pair does not degrade significantly, even as the network serves a growing number of users. This architecture is one of the results we get from a multi-parameter scaling law study of the information-theoretic capacity of wireless networks. More generally, this study allows us to identify the fundamental operating regimes of wireless networks and the scaling optimal communication strategies in each of these regimes. The optimality of such strategies is established by proving tight upper bounds on the best achievable capacity scaling in wireless networks.