Energy-efficient cooperative relay protocols for wireless sensor networks

In this thesis, a new cooperative transmission scheme based on the data exchange between relays (fDSTC) is proposed. Thorough comparisons of this fDSTC protocol and more classical distributed space-time codes (cDSTC) protocols in case of non-regenerative relays (NR-relays) and regenerative relays (R-relays) are considered in terms of error performance, outage probability, diversity order and energy consumption via both numerical simulations and mathematical analysis. In addition, the fDSTC protocol is applied to multi-antenna systems and shown to be more energy-efficient than the cDSTC protocol using either a typical energy model widely-used in the literature or a realistic energy model based on the PowWow platform. Besides, a mathematical analysis in terms of energy consumption is complementarily given to show how to choose the best cooperative models to prolong the lifetime of WSNs. As MAC protocols have a great influence on the total energy consumption of the networks, that leads to a big motivation to design a cooperative MAC protocol, RIC-MAC, by combining preamble sampling and cooperative relay techniques. The analytic results still confirm the interest of using cooperative relay techniques, but their energy efficiency may be affected by the MAC protocol design, the traffic loads of the networks and the desired latency.