Research On PAPR Reduction In Orthogonal Frequency Division Multiplexing System

With the rapid development of wireless communication technology,orthogonal frequency division multiplexing(OFDM) technology is increasingly more attention of native and foreign researchers. OFDM technology is a special multi-carrier transmission technology, which has a higher resistance to multi-path interference, a higher spectrum efficiency and a higher data transmission efficiency. However, the high peak to average power ratio(PAPR)becomes a bottleneck that limits the development widely of the OFDM technology. Because when the high amplitude of the signal goes into the nonlinear region of high power amplifier(HPA), which can produce nonlinear distortion, decrease the bit error rate(BER) performance, and thereby affect the overall performance of the system, so it is particularly important to reduce the PAPR effectively in practical applications of OFDM technology.This paper researches mainly on the PAPR reduction method of low computational complexity for the high PARP. The main work is as follows:(1) For the current problem of high PAPR, PAPR reduction techniques of OFDM system are major divided into three categories, signal prewarping class,encoding class, probability class technology. Theoretical analysis and simulation results show that the methods could reduce PAPR, but they have certain deficiencies.(2) This paper presents an improved PTS algorithm based on the existing partial transmit sequence(PTS) algorithm for PAPR reduction. Firstly, the method inserts a pilot sequence with cyclic shift in the sub-block sequence of PTS respectively, looking for optimal coefficient of PTS algorithm using sub-optimal combination algorithm; then by the shift processing cycle,comparing the PAPR of the resulting signal with the setting threshold value respectively; finally, it can obtained PAPR which meets the requirements.Theoretical analysis and simulation results show that the improved algorithm can not only ensure the BER performance, but also can effectively reduce PAPR.(3) Focusing on the problem of high computational complexity in coefficient optimization of PTS technology, this paper proposes a new P-SLM algorithm that uses selected mapping(SLM) algorithm based on PTS technology.Theoretical analysis and simulation results show that the algorithm can get better PARP than SLM, PTS algorithm without increasing the number of IFFT operations.