End-to-End Theoretical Evaluation of a Nonlinear MIMO-OFDM System in the Presence of Digital Predistorter

Wireless communication systems are inherently nonlinear due to the presence of high power amplifier (HPA) at the transmitter. The impact of nonlinearity is more severe for the case of high peak-to-average-power ratio waveforms, such as orthogonal frequency division multiplexing (OFDM). A digital predistorter (DPD) is generally used to mitigate the nonlinear distortions caused due to the HPAs. However, most of the prior work on performance evaluation of cascaded DPD+HPA architecture has been restricted to computer simulations with a trivial analytical contribution. In this paper, we evaluate the end-to-end performance of a multi-input-multi-output OFDM system impaired by nonlinear HPAs in the presence of DPD. To represent the behavior of the cascaded DPD+HPA architecture, a joint nonlinear polynomial model is proposed. It has been shown that the received signal through the cascaded DPD+HPA architecture constitutes a residual noise as well as a multiplicative factor. The residual noise depends on the nonlinearity order of DPD, whereas the multiplicative factor depends on the gain of the HPA and DPD. Furthermore, by modeling the residual noise as a complex Gaussian process, an end-to-end analytical methodology has been proposed to evaluate symbol error rate of the complete system for a multipath Rayleigh fading channel.