The Research On The PAPR Reduction Optimization Schemes With Low Computational Complexity For OFDM Systems

In practical applications, Orthogonal Frequency Division Multiplexing (OFDM)suffers from high peak-to-average power ratio (PAPR) issues. A large PAPR requires alinear high power amplifier (HPA), which, however, is inefficiently used. Moreover, thecombination of an HPA having insufficient linear-range and a large PAPR leads to bothin-band distortion and out-of-band radiation. Therefore, various PAPR reductiontechniques have been proposed.In this paper, we proposed two kinds of novel PAPR reduction schemes with lowcomputational complexity for OFDM systems.The first kind scheme is an improved tone reservation method, which is based on theleast squares approximation. Compared with the clipping control method, the proposedscheme can generate the optimal peak-cancelling signals with fast convergence.Simulation results show that the proposed scheme only needs two iterations at most toachieve almost the same PAPR reduction as that of the clipping control method.The second kind scheme is a novel subblock linear combination (SLC) scheme,which is based on the cyclic projections algorithm. To accelerate the convergence rate ofthe SLC scheme, an improved SLC method with a relaxation factor, named as the R-SLCscheme, is also proposed in this paper. The key idea of the two novel methods is to dividean OFDM block into several subblocks, and iteratively generate the linear combination ofthese subblocks with lower PAPR. After several iterations, a desirable PAPR reduction isachieved. Compared with the traditional partial transmit sequence (PTS) scheme, thecoefficients of the linear combination with the proposed schemes are obtained by iterativecalculation with the cyclic projections algorithm, instead of by exhaustive searching andselecting in the preset discrete set. Therefore, one big advantage of the proposed schemesis that the computational complexity is much lower than that of the traditional PTSscheme. According to the theoretical analysis and simulation results, these two kinds ofproposed schemes could offer good performances of PAPR reduction and bit-error-ratewith low computational complexity.