Energy Efficiency vs Spectral Efficiency Tradeoff in Multi-user MIMO-OFDM Systems with Hardware Nonlinearities

Energy efficiency (EE) is a fundamental design criterion in multi-user multipleinput multiple-output (MU-MIMO) systems. Accurate evaluation of EE requires a comprehensive end-to-end (E2E) model that accounts for practical hardware impairments such as finite-resolution analog-to-digital converters (ADCs)/digital-to-analog converters (DACs) and non-linear operation of power amplifiers (PAs). In this work, we first develop a hybrid beamforming algorithm for a MU-MIMO-orthogonal frequency division multiplexing (OFDM) system with the aim of maximizing the total spectral efficiency (SE) of the users and reducing the multi-user interference (MUI). To evaluate the EE of the system, we then develop an E2E model that considers the joint impact of finite-resolution DACs, ADCs, and nonlinearity in PAs. The DACs/ADCs behavior is expressed using the additive quantization noise model (AQNM), while Bussgang decomposition is used to characterize PA nonlinearity. Simulation results provide insights into the impact of hardware impairments on the EE-SE trade-off, highlighting critical design considerations and performance trade-offs for energy-efficient system implementations.