Research On PAPR Reduction Of FRFT-OFDM System

Orthogonal Frequency Division Multiplexing (OFDM) based on the Fractional Fouriertransform (FRFT-OFDM) not only has the same advantages with traditional OFDM, but theperformance of the system is enhanced compared to traditional OFDM system while twosides have larger relative motion speed between send and receive, that is the system has theDoppler frequency shift. But the FRFT-OFDM system also has high peak to average ratio(PAPR). The problem leads to nonlinear distortion. The traditional solution uses a linearhigh-power-amplifier with an extremely high dynamic range, which is expensive andinefficient.This paper focuses on the domain of PAPR reduction of FRFT-OFDM system，deducesformula of distribution character theoretically, proposes a PAPR reduction method withlow-complexity. And a FRFT-OFDM system model is built and the studied methods aresimulated by MATALB. The main work can be summarized as follows:1) This paper expounds the basic principle and system model of FRFT-OFDMtechnology. Firstly the paper introduces the definition of fractional Fouriertransform and the related theorem, and then details the principle and systemcomposition of FRFT-OFDM technology.2) Deduces formula of distribution character theoretically; Summarizes the existingPAPR reduction technology of FRFT-OFDM technology, describes in detail theprinciple of each method, carries on the simulation verification for each method,and carries on the analysis and comparison for existing PAPR reductiontechnology in the reliability computation,complexity, transmission efficiency.3) Introduces cyclically shifted phase sequences (CSPS) and optimized CSPS(OCSPS) technologies of traditional OFDM system; Drawing lessons from theCSPS and OCSPS technology principle, this paper proposes a PAPR reductionmethod with low complexity for FRFT-OFDM system according to thecharacteristics of the FRFT-OFDM technology. The method based on fractionalrandom phase sequences (FRPS) and fractional circular convolution theorem,which is called FRPS method, requires only one N-point inverse discretefractional Fourier transform (IDFRFT), and all candidates can be calculateddirectly in time domain. The method avoids executing many N-point IDFRFT operations in parallel. Simulation results show that our scheme can maintain thereliability of the system; PAPR performance becomes better with increasing valueof L. The PAPR performance of the proposed method was found to be almost thesame as that of Selecting Mapping (SLM) and better than that of Partial TransmitSequence (PTS). More importantly, the proposed method has lower computationalcomplexity.