Energy efficiency analysis of cooperative ARQ in Amplify-and-Forward relay networks

In this paper, the energy efficiency of cooperative ARQ transmission in Amplify-and-Forward (AF) relay networks is discussed. The average total energy consumed per bit for cooperative ARQ under Quality of Service (QoS) constraints is formulated. With numerical method, the objective is optimized over the transmission data rate, the transmit power of the source and the relay, given fixed maximum retransmission number. Then, performances of various maximum retransmission numbers are analyzed. Simulation results demonstrate that cooperative ARQ with large maximum retransmission number has solid capability to save energy when the transmission energy plays a dominant role compared to circuit energy. However, for energy saving, small maximum retransmission number should be adopted on condition that tight maximum average transmission delay constraint is imposed.