Random phase updating algorithm for OFDM transmission with low PAPR

Abstract

A novel random phase updating algorithm for reducing the peak-to-average power ratio (PAPR) of OFDM signals is addressed. The phase of each subcarrier is updated by a random increment until the PAPR goes below a certain threshold level. We investigate the influence of different distributions for the phase increments and the variance of distributions on the mean and variance of PAPR as well as the number of iterations to reach the threshold. Further, the random phase updating algorithm has been extended by dynamically reducing the threshold level. After successful updating of the phase shifts, the threshold level is reduced and the variance of the phase increments is changed. Simulation results of the algorithm are provided. It is shown that the random phase updating algorithm with dynamic threshold gives the best results and can reduce the mean power variance of an 8-carrier OFDM signal with BPSK modulation by a factor of 7 dB. In order to reduce the complexity, the random phase updating algorithm is investigated with quantization and grouping of the phase shifts. Results show that for a 16-carrier OFDM system, 2-level quantization of phase shifts in 8 groups of 2 carriers give no significant increase in the power variance while reducing complexity. Further, the impact of phasing on the bit error rate performance of the OFDM system is studied.