Energy efficiency of amplify-and-forward relaying with antenna selection and beamforming

A transmission scheme´s energy efficiency (EE) is closely related to the number of active transmit antennas. Activating more transmit antennas can reduce transmit power at the expense of higher circuit power. This trade-off may become more complicated with cooperative diversity considered. In this paper, we consider a dual-hop amplify-and-forward (AF) relay network and its EE performance is analyzed when different transmission schemes are deployed. For each scheme, the analytical expression for the probability density function (PDF) of receive signal-to-noise ratio (SNR) at the destination is derived. The corresponding spectrum efficiency (SE) and EE performance of system are also evaluated. We further discuss the impact of total antenna number, target SE and large-scale fading on the system´s EE based on numerical results.