On Maximum of Energy-Efficiency in Amplify-and-Forward Relay Networks under Channel Estimation Errors

In this paper, we investigate the energy-efficiency for amplify-and-forward relay networks in the presence of channel estimation errors. Two kinds of transmission strategies, i.e., direct transmission (DT) and relay transmission (RT), are dealt with for the energy-efficient communication system design. The energy cost function in DT or RT is defined as the total energy consumption for transmitting one bit data successfully, in which the channel estimation error, the channel estimation cost (i.e., energy consumed for pilot transmission) and the outage probability are included. As the power allocation plays a crucial role in implementing relay networks in an energy-efficient manner, we propose a theoretical framework for energy-efficient power allocation in DT and RT strategies to minimize the energy cost. By simulation, we compare the two transmission strategies according to the energy cost under various network scenarios. Our results provide several insights into the choice between DT and RT strategies if some transmission parameters are known.