An Analysis of the Tradeoff Between the Energy and Spectrum Efficiencies in an Uplink Massive MIMO-OFDM System

This brief mainly investigates energy efficiency (EE) and spectrum efficiency (SE) for the uplink massive multiple-input-multiple-output orthogonal frequency-division multiplexing system in a single-cell environment. An approximate SE expression is first derived by employing the maximum ratio combination or zero-forcing detection at the base station. Then, the theoretical tradeoff between EE and SE is established after introducing a realistic power consumption model in consideration of both the radiated power and the circuit power. Based on the tradeoff, the optimal EE with respect to SE is derived using the convex optimization theory. Results show that the optimal EE increases by deploying a suitable number of antennas, multiplexing a reasonable number of users, expanding the system bandwidth, or shrinking the cell radius. Partly different from the EE, the SE corresponding to the optimal EE can be improved by increasing the number of antennas, multiplexing a rational number of users, narrowing the system bandwidth, or shrinking the cell radius.