Reliable and energy-efficient cooperative transmission in wireless sensor networks

In this thesis, we propose a cooperative relay scheme for multihop communications in wireless sensor networks. The scheme investigates node cooperation in conjunction with power control to conserve transmission energy and improve communication reliability in the presence of fading. By using relay nodes that are located between transmitter and receiver to assist packet delivery, the scheme is capable of reaping both spatial diversity gains and pass-loss savings. Local channel information is explored in relay selection process and power control to reduce the energy of data packet transmission. Moreover, a cooperative ARQ is incorporated to improve packet retransmission efficiency. We analyzed packet delivery ratio and energy consumption, and observed good agreement between analytical and simulation results. In simulations, we compared different cooperative and non-cooperative schemes and examined effects of various factors. Our simulations and analyses show that the proposed scheme improves energy efficiency, packet delivery ratio and extends nodes' battery lifetime.