Multiterminal relay networks: Performance bounds, protocol design, and channel coding strategies.

The combination of silicon scaling and energy-efficient multi-terminal packet radio technology will soon allow low power devices to be embedded virtually everywhere, enabling a wide range of revolutionary applications that will radically change the way that people and devices interact with their environments. Given current trends in the advancement of technology, to engineer useful embedded wireless networks with long lifetimes and massive scale required for many applications, new analytical tools and approaches to protocol design that reflect recent perspectives on wireless networking are necessary. The major objective of this dissertation is to characterize the fundamental performance bounds and devise an integrated approach to the design, analysis, and implementation of energy efficient cross-layer protocols for embedded networks under realistic constraints. The focus of the study is on a general class of embedded wireless networks that are decomposed into clusters of low cost radio devices including a source, a destination, and one or more relays. The message propagation mechanism of each cluster is modelled as a rate constrained relay network where signaling is over a random phase block interference channel, and transmissions from the various nodes are noncoherent. Numerical analysis indicates that even in relay networks under small rate constraints, significant energy savings are achievable by implementing distributed spatial diversity via adaptive or nonadaptive relaying. For relay networks under large rate constraints, we propose energy-efficient relaying protocols that jointly perform cooperative diversity, hybrid-ARQ retransmission, and routing, first for time-invariant networks to exploit a better energy-throughput tradeoff over multihop or direct transmission, and then for time-varying networks to fully implement the time and spatial diversity with energy constrained devices. Unlike multihop, where a network-layer protocol is needed to explicitly select a message route through the network a priori, relaying will adaptively find the best ‘path’, thus bypass relays that are continually in an outage, thus power/range control becomes less important in relay networks. On the other hand, as relaying requires many more devices than multihop to listen to each broadcast, its energy efficiency benefit begins to diminish due to non-negligible energy cost to receive a transmission. To avoid excessive receiver energy dissipation, the coverage area and cluster size of relaying need to be carefully defined. Finally, we propose simple coding strategies inspired by the turbo principle is proposed to approach the information theoretic limits of the constrained relay networks under block fading