Sub-Optimum Cyclically Shifted Sequences for PAPR Reduction in OFDM Systems

Partial transmit sequence (PTS) method requires the exhaustive search over all combinations of allowed phase factors, and the search complexity increases exponentially with the number of sub-blocks. To solve this problem, on the basis of studying cyclically shifting partial transmit Sequences (PTS/CSS) and Sub-optimum PTS method (sub-OPTS), a sub-optimal cyclically shifted sequence (sub-OPTS/CSS) method is presented. In our scheme, a cyclic shift of the fast Fourier Transform (FFT) in the time domain is employed to improve the PAPR reduction performance. Furthermore, phase factors are optimized only for latter half of candidates, so as to reduce the complexity. The comparison of subOPTS/CSS method with some methods is carried out from the number of candidates, the redundancy and the computational coats. The analysis and simulation results show that, in the case of the same number of subblocks and phase weighting factors, sub-OPTS/CSS is almost the same as the performance compared with PTS/CSS method while the processing time of iteration is reduced by 50%.Sub-OPTS/CSS achieves better performance than sub-OPTS method.