Iterative precoding of OFDM-MISO with nonlinear Power Amplifiers

A novel iterative algorithm for transmitter (TX) precoding for a Orthogonal Frequency Division Multiplexing - (OFDM-) Multiple Input Single Output (MISO) system with nonlinear Power Amplifiers (PAs) is proposed. Having a plurality of PAs at the TX, it is possible to synthesize peak power limited signals, transmitted at each TX branch, such that the total distortions seen at the receiver (RX) will be minimal. Two versions of the algorithm are proposed. The first one reduces nonlinear distortions seen at the RX antenna without considering the spectral purity requirements. The second one reduces nonlinear distortions at the RX and also keeps the out-of-band radiation of the TX signals at a low level in order to satisfy spectral purity requirements. For a low Back-Off (BO) scenario, where the nonlinear distortions are strong, the proposed algorithms show a much lower Symbol Error Rate (SER) and much higher power efficiency than the well known Maximum Ratio Transmission approach.