Energy-efficiency of Very Large Multi-user MIMO systems

Energy efficiency is becoming increasingly important for wireless communications as mobile devices are battery-constrained. Motivated by this, in this paper we consider uplink energy-efficient resource allocation in Very Large Multi-user MIMO systems. Specifically, both the number of antenna arrays at BS and the transmit power at the user are adjusted to maximize the energy efficiency, in which the power consumption accounts for both transmit power and circuit power. We demonstrate the existence of a unique globally optimal number of antenna arrays at BS and the transmit power and provide iterative algorithms to obtain it. Our simulation results show that the performance of the proposed algorithms is close to the optimum, while having low complexity. It is also found that the distance between the base station and the users plays an important role in increasing the energy efficiency, namely, the energy efficiency is increasing with the distance decreasing.