Research On PAPR Reduction Techniques For OFDM System In Satellite Communications System

Orthogonal frequency division multiplexing(OFDM) is a parallel transmission scheme of MCM(Multi-Carriers Modulation). OFDM has been a very wide range of applications as the core of 4G. OFDM is very suitable for using in satellite communications system because OFDM system can get more immunity to multi-path fading and has high utilization of frequency spectrum. However, the major drawback is that its signal waveform has a high peak-to-average power ratio(PAPR) which causes severe nonlinear distortion in actual devices such as high power amplifier(HPA).This paper focuses on the domain of PAPR reduction of OFDM signals. In this paper, an OFDM system model is built by MATLB and the PAPR problem is studied by simulation.Firstly, the principle, OFDM technology in the field of satellite communications developments are introduced in the paper, and then the definition and distribution characters of PAPR are analyzed. The advantages and disadvantages of OFDM technology are introduced too. At the same time, it discusses three kinds of major technologies to reduce the high PAPR: signal pre-distortion techniques, code techniques, and scrambling techniques. SLM and PTS, which are scrambling technique, are analyzed, and they are researched by simulation. Secondly, in order to reduce the PAPR, the tone reservation is analyzed in the paper and researched by simulation. Furthermore, the precoding and spectrum shaping methods for PAPR reduction are studied in the paper. The DFT-precoding and spectrum shaping schemes are compared by simulation.At last, in order to reduce the PAPR, two novel combined algorithm are proposed in this paper. The simulation shows these algorithm can get good PAPR reduction performances.