Research On PAPR Reduction Techniques For OFDM System

Orthogonal frequency division multiplexing (OFDM) is a special paralleltransmission scheme of MCM (Multi-Carriers Modulation). OFDM has been regardedas one of the core technologies for the next generation communication system becauseOFDM system can get more immunity to multi-path fading and has high utilization offrequency spectrum. However, the major drawback is that its signal waveform has ahigh peak-to-average power ratio (PAPR) which causes severe nonlinear distortion inactual devices such as high power amplifier (HPA). This paper focuses on the domain ofPAPR reduction of OFDM signals. In this paper, an OFDM system model is built byMATLB and the PAPR problem is studied by simulation.Firstly, the principle，the advantages and disadvantages of OFDM technology areintroduced in the paper, and then the definition and distribution characters of PAPR areanalyzed．At the same time, it discusses three kinds of major technologies to reduce thehigh PAPR： signal pre-distortion techniques， code techniques， and scramblingtechniques. The advantages and disadvantages of them are analyzed and some classicalalgorithms are particularly researched by simulation．In order to improve the BER performance of the signal pre-distortion techniques,iterative receiver is discussed to estimate and cancel the distortion caused bypre-distortion noise. The proposed method is applied to clipped and companded OFDMsignals. It is shown by simulation that the system performance can be obviouslyimproved. Furthermore, the precoding and spectrum shaping methods for PAPRreduction are studied in the paper. The performance of different precoding and spectrumshaping schemes are compared by simulation.At last, in order to aggressively reduce the PAPR, a novel combined algorithm isproposed in this paper. The simulation shows this algorithm can get good PAPRreduction performances with not large BER performance lost．...