Simulation And Research On Reduction Of The Peak-to-Average Power Ratio Of OFDM System

OFDM (orthogonal frequency division multiplexing) is a parallel transmission scheme of MCM ( Multi-Carriers Modulation). It transmits information through orthogonal multiple sub-carriers and has high utilization of frequency spectrum, good capability of countering multi-path interference. It is also adaptive to high-rate data transmission and multimedia data transmission. This technology has been regarded as the core technology of 4G wireless communications system in the future. However, it has high peak-to-average power ratio (PAPR), which is its inherent disadvantage. This disadvantage in OFDM systems has limited OFDM' S wide applications and has not been solved yet. This paper has mainly researched on the methods of PAPR reduction for OFDM and has obtained some results by MATLAB simulations.The fundamental principle of DFT-based OFDM system and its key techniques are introduced in this thesis. Then, the definitions and distributions of PAPR are analyzed by simulation. A lot of literature on PAPR reduction for OFDM has been summarized and has been categorized into 3 classes. The representative methods in every class have been researched. In signal distortion techniques, clipping is analyzed in terms of two performance measures: complementary cumulative distribution function (CCDF) and bit error rate (BER). SLM (selective mapping) and PTS (partial transmit sequence) are compared by simulation in signal scrambling. This comparison provides proofs of theory for practical. In order to reduce the large computation complexity of PTS an improved method—iterative shifting linear-searching based on random sub-block division has been analyzed and compared with customary PTS via computer simulation. The result of simulation shows that this improved PTS method is a kind of advanced PTSand achieves a good compromise between PAPR performance and computation complexity. A coding scheme based on Golay complementary sequences and Reed-Muller codes is proposed to reduce the PAPR in coding technologies. The result of simulation testifies that this scheme can control the PAPR value of OFDM signal in 3dB. Finally, the relative research and simulation about the whole paper is summarizes, meanwhile, the further practically research in future is expected.