BER Analysis and Compensation for the Effects of Polynomial HPA Non-linearity in MIMO OFDM Systems Over Fading Channel

The nonlinearities caused by the High Power Amplifier (HPA) has a crucial effect on the performance of Multiple Input Multiple Output (MIMO) with Orthogonal Frequency Division Multiplexing (OFDM) systems. In this paper, we investigate the performance of Vertical Bell Laboratories Layered Space-Time (VBLAST) MIMO OFDM systems in the presence of non HPA which is modeled as a NL polynomial model. Specifically, we present a theoretical analysis of NL distortion effects in VBLAST MIMO OFDM systems in terms of error probability and system capacity. Therefore, we propose a nonlinear distortion compensator based on Neural Network (NN) accompanied with Minimum Mean Square Error receiver which corrects this nonlinearity. In the fact, the correction is done at the transmitter after HPA and at the receiver level after OFDM demodulation in frequency and time domain. Also, we present the structure of the NN adapted to both the predistortion and frequency domain. Simulation results show the comparison between the theoretical and simulated of nonlinear distortion effects in MIMO-OFDM transmission systems, as well as the performance of different methods of compensation proposed.