Energy efficient transmission for DF MIMO relay systems with antenna selection

This paper investigates the maximization of energy efficiency (EE) in decode-and-forward (DF) MIMO relaying systems with antenna selection. An iterative EE maximization algorithm is proposed to jointly select the active receive and transmit antennas at the relay, as well as optimize the transmission power of the source and relay. In particular, the antenna selection relies on a derived iterative property of EE, which guides us to select a pair of one receive and one transmit relay antennas that achieves the largest increment of EE under an initial transmission power. There is also a power adaptation for each iteration where we calculate the optimal transmission power and then set it as the initial one for the next iteration. In this process, the tool of fractional programming is used to find the maximum EE and the corresponding transmission power for each iteration. Simulation results show that the proposed algorithm achieves near-optimal performance at all the transmission distances. Moreover, it is capable of simultaneously improving EE and reducing the power consumption for transmission.