Improved SPW and predistortion to overcome the nonlinear distortion of the OFDM communication system

Because of so many sub-carriers, OFDM signal has very wide amplitude distribution. Even though the predistortion is used to compensate for the HPA nonlinearity, the power efficiency of the HPA (high power amplifier) is still very low since the PAPR (peak to average power ratio) is very high. So, reduction of the PAPR of the OFDM signal before the predistortion will improve the power efficiency and nonlinear compensation. In this paper, we propose a new combined method of SPW (subblock phase weighting) for PAPR reduction and predistortion technique. That is an improved SPW method to use a novel weighting factor combination of the complementary sequence characteristic plus PAPR threshold technique. From the simulation results, BER performance is improved and in-band and out-of-band spectrum radiations are mitigated. Power efficiency of HPA is enhanced because of the PAPR reduction. So, the proposed system improves about 3dB and 1dB performance than the LCP (linearized constant peak-power)-OFDM and LCP-OFDM plus SPW at BER=10⁻⁴.