Research And Improvement On PAPR In OFDM System

As wireless communication technology comes into4thgeneration. Voice, image and dataas well as their combination of multimedia services are more and more popular, it makeshigh-speed data transmission technology has become a hot spot in research. Since OrthogonalFrequency Division Multiplexing (OFDM) technology has a good performance with antennamultiple interference and efficient spectrum utilization, it gets more and more attention fromresearchers.The basic principle of OFDM is that firstly the high speed serial data stream is dividedinto a plurality of parallel, low speed data stream, and these parallel data streams are mappedonto a set of orthogonal subcarriers, In this way the original channel is transferred into anumber of equal bandwidth sub-channels. The time duration of OFDM symbol is much longerthan the duration of a single carrier symbols. Therefore OFDM anti-multipath interferenceperformance is much better than single carrier anti-multipath interferes. But OFDM symbolalso has some disadvantages, because the output signal is a combine of multiple sub-carriers,OFDM system has a large peak to average power ratio (PAPR). The high PAPR will generatedistortion signal, so it is necessary to reduce OFDM system PAPR.This paper primarily makes a study on how to reduce the PAPR of OFDM system. Firstly,paper shows an overview of the historical development of OFDM, and then introduces theprinciples and key technologies of OFDM system; also explain the distribution characteristicsof peak to average power ratio in OFDM system. Then paper has a discussion with reducingthe PAPR of OFDM system, it includes clipping, filtering and SLM methods, etc. and thesealgorithms are verified by practical simulation.This paper proposes two algorithms about PAPR reduction in OFDM system, the firstone is an improved clipping algorithm, and the second method is a combination algorithm ofSLM and advanced clipping method. It ensures that the OFDM system has a more effectivePAPR reduction performance based on the smaller system bit error rate. Finally, the result ofsystem simulation indicates that the proposed combination algorithm reduces the PAPReffectively, the bit error rate is lower than the traditional clipping method’s bit error rate.