A memory mapping predistorter for the compensation of nonlinear distortion with memory in OFDM systems

Abstract

A computationally efficient memory mapping predistorter is proposed to compensate for nonlinear distortion with memory induced by a combination of a linear pulse shaping filter and a travelling wave tube amplifier in orthogonal frequency division multiplexing (OFDM) systems. The proposed scheme utilizes a look up table (LUT) to store a small number of pre-calculated input-output relationships of the predistorter based on the fixed point iteration (FPI) we have presented in other study, and a simple memory mapping is employed for the data during actual system operation. We have implemented a 16-QAM, 256-subcarrier baseband OFDM modem and the proposed predistorter on a Texas Instruments' TMS320C30 digital signal processor, and experimental results show that the proposed predistorter achieves a very close performance of that based on the FPI even with a small LUT, while drastically reducing the computational complexity.