Esquemas de comunicação cooperativa com múltiplos relays e múltiplas antenas visando a eficiência energética

Abstract

Wireless sensor networks are usually composed of devices that require transmission quality, but with limited energy. From this condition arises the necessity of the energy efficiency study. In this document, we present and compare some techniques to improve the energy efficiency, which include the use of diversity, such as the use of multiple antennas in the transmitter and receiver as well as the use of cooperative communication. The latter has better results when a feedback channel is available. We cover two communication scenarios. In the first scenario, only the physical layer is taken into account in a MIMO cooperative network with multiple relays, where we propose a power allocation distributed iterative algorithm based on the Dinkelbach’s algorithm aiming at the energy efficiency maximization. The results show that the use of multiple antennas improve the energy efficiency, but depending on the used MIMO transmission scheme, the number of relays and the number of antennas can lead to different effects with respect to the energy efficiency. In the following, we present a scenario that contains a cross-layer analysis encompassing physical and medim access control (MAC) layers in a cooperative MIMO network, where we propose a distributed cooperative MAC protocol. In this case, besides the energy used to transmit thte data packets, we also analyze the delay and energy consumption to access the channel. Results show that the MIMO techniques improve the energy efficiency when we compare to SISO, especially when employing antenna selection techniques. In addition, other parameters, such as node density, spectral efficiency, number of antennas and distance between nodes, are analyzed with respect to the energy efficiency.