Energy Efficiency of mmWave MIMO Systems With Spatial Modulation and Hybrid Beamforming

Abstract

This work addresses the problem of energy-efficient radio resource allocation in large-scale multiple-input multiple-output (MIMO) systems using hybrid beamforming and spatial modulation, communicating using mmWaves. The problem is formulated as the maximization of the bit-per-Joule energy efficiency with respect to the transmit power and number of active radio-frequency (RF) chains, enforcing constraints on maximum power, maximum and minimum number of active RF chains, and minimum achievable rate guarantee. The optimization is carried out considering both the standard linear power consumption model, as well as the case in which the transmit amplifier operates in the non-linear region. In both cases, the globally optimal solution is derived with affordable complexity. Numerical results confirm the optimality of the proposed optimization framework, showing that spatial modulation with hybrid beamforming is more energy-efficient than a hybrid beamforming system without spatial modulation for realistic hardware power dissipation values.