Maximizing Energy Efficiency for Multiple DF Relay System with QoS Constraint

Abstract:
Multiple relays assisted transmission is an effective way to enhance the reliability of wireless communication network. However multiple relays joining in the transmission costs more energy and may reduce the energy efficiency of the system. In this paper, we investigate the energy efficiency performance of multiple decode-and-forward relays system under a quality of service constraint. In particular, we study a feedback-limited scenario where only the knowledge of average channel gain is available at the source. First, we define a tradeoff factor and based on it design a tradeoff mechanism between energy efficiency and outage probability. Second, we prove that the energy efficiency of the system is a piecewise strictly monotonic function of our tradeoff factor and has only one extreme value which is the global maximum. Third, by means of simulation we show that the numerical results perfectly match our theoretical analysis. In addition, we show that energy efficiency can achieve the extreme value under the loose QoS constraint.