Employing antenna selection to improve energy efficiency in massive MIMO systems

Massive MIMO systems promise high data rates by employing large number of antennas. By growth of number of antennas in a system, both data rate and power usage rise. This creates an optimisation problem which specifies how many antennas we should have for an optimum operation to achieve the best possible Energy-Efficiency. Since the number of user terminals varies over time, number of operational antennas should be optimised continuously while there exists a fixed number of antennas installed in the BS. In this paper, we propose to select appropriate number of antennas in an adaptive manner relative to number of user terminals. Through this, existence of excessive number of antennas can be used to select best antennas which have better channel conditions. This can improve Energy-Efficiency due to better use of available resources. Next, we find a tight approximation for consumed power using Wishart theorem for the proposed scheme and use it to find a deterministic form for Energy-Efficiency, correspond to our proposed algorithm. Our simulation results show that our approximation is quite tight and there is significant improvement in Energy-Efficiency when antenna selection scheme is employed.