Resource optimization for energy efficiency in multi-cell massive MIMO with MRC detectors

In this paper, resource allocation for energy-efficient communications in a pilot-contaminated uplink multi-cell massive MIMO system with MRC detectors is investigated. The problem of maximizing energy efficiency (EE) of data transmissions in the system is studied by optimizing the number of antennas per BS, the pilot signal power, and the data signal power. The considered optimization problem takes into account the circuit power consumption, pilot contamination, and budget constraints in the number of antennas per Base Station (BS) and the average transmission power per symbol. The resulting optimization problem has a non-convex fractional objective function which is difficult to solve in its original form. Therefore, principles from fractional programming are used to first transform the problem into an equivalent parametric form and then to derive an iterative resource allocation algorithm. In each iteration, an alternating optimization technique is used to solve the objective function by decomposing it into a sequence of solvable difference of convex (D.C) programming subproblems. Simulation results show that higher EE levels can be achieved by optimizing the pilot and data powers separately. Also, increasing the number of antennas per BS with the power budget may or may not be energy-efficient, depending on the range of operation.