OFDM peak-to-average power ratio reduction by combined symbol rotation and inversion with limited complexity

A signal scrambling method based on combined symbol rotation and inversion (CSRI) is proposed in this paper for the peak-to-average power ratio (PAPR) reduction of OFDM signals. By dividing OFDM sequences into subblocks and performing symbol rotation and inversion in each subblock, high degrees of freedom are available to offset the possibility of encounting poor sequences with large PAPR. In order to reduce the complexity of this scheme, two suboptimal CSRI schemes; one based on a successive approach combined with symbol grouping, termed successive suboptimal CSRI (SS-CSRI) and another based on a random approach combined with threshold control, termed random sub-optimal CSRI (RS-CSRI) are also investigated. With these two schemes, the complexity can be reduced significantly with only slight performance degradation. Compared with the partial transmit sequence (PTS) scheme, simulation results show that performing symbol rotation is more effective for PAPR reduction than increasing the number of phase weighting factors with PTS.