Compensation of power amplifier nonlinear distortion in spatial modulation systems

Abstract

Power amplifier (PA) nonlinearity plays a crucial role in determining the performance of radio frequency (RF) communication systems. Specifically, PA nonlinearity causes the amplitude-phase modulation (APM) constellation points to get distorted, which results in performance degradation. In this paper, we study the effect of PA nonlinearity on the bit error performance of spatial modulation MIMO (SM-MIMO) systems. When the PA distortion parameters are perfectly known at the receiver, the optimal detection rule is the one which minimizes the maximum-likelihood (ML) cost over the distorted constellation. For the case when the receiver has no knowledge of PA distortion parameters, we propose a receiver compensation technique which involves estimating the points of the distorted APM constellation based on training and performing detection using the estimated constellation. Simulation results show that, for SM-MIMO with 16-QAM, the proposed scheme achieves almost the same bit error performance as that achieved using the perfect knowledge of the PA parameters. Also, the proposed scheme is found to perform within 2-4 dB of the performance achieved using an ideal (linear) PA even at low values of input backoff.