Research On PAPR Suppression Technology For High-Speed OFDM Transmission System

In recent years,with the rapid development of emerging communications services such as smart homes,autonomous driving,and ultra-high-definition network video live broadcasts,people's demand for wireless communications systems with “high throughput,high reliability and millisecond delay” has become more and more urgent.The OFDM technology with the characteristics of “high frequency band utilization,strong anti-interference ability and high-speed data processing” has become a current research hotspot.However,for the “ultra-large bandwidth and massive throughput” high-speed OFDM transmission system,with the sharp increase in the number of sub-carriers and the trend toward higher-order modulation methods,the problem of signal PAPR(Peak to Average Power Ratio)has become more and more serious.Aiming at the challenges faced by PAPR suppression technology in high-speed OFDM transmission systems,this paper focuses on the PAPR suppression technology based on Partial Transmit Sequence(PTS)from the perspectives of improving PAPR suppression gain and reducing technical complexity and time delay.The traditional PTS algorithm is optimized and improved from the aspects of block method,phase factor search process and algorithm jointness.First,the paper studies the new signal characteristics of high-speed OFDM transmission systems and the challenges faced by PAPR suppression technology.Comprehensively considering factors such as suppression gain,complexity,processing cycle,high-performance PAPR suppression scheme of PTS technology is designed for the system with “large carrier,high-order modulation and low delay”.Secondly,in view of the shortcomings of existing PTS algorithms such as insufficient PAPR suppression gain,high computational complexity and lack of flexibility,a PTS optimization algorithm based on Logistic chaotic pseudo-random block and Monte Carlo tree phase factor search is proposed.The new algorithm is based on the basic architecture of the traditional PTS algorithm,and optimizes the traditional PTS algorithm from two aspects: the block method and the phase factor search process: On the one hand,a pseudo-random block method based on Logistic chaotic sequence is proposed.The frequency domain data is divided into blocks based on the value after multi-bit extraction of Logistic chaotic sequence and Gray mapping,thereby reducing the complexity of block and ensuring the time domain.The randomness of the sub-block sequence prepares for the phase factor search process;on the other hand,a phase factor search algorithm based on Monte Carlo tree is proposed,which makes full use of the relevant posterior information generated during the phase factor search process to assist in guiding the algorithm.Search direction,thereby improving the search accuracy of the algorithm and reducing the number of searches required for the algorithm to obtain the same PAPR gain.The new algorithm has excellent PAPR suppression performance,lossless BER performance,low complexity and good flexibility,and it is suitable for various high-speed and reliable OFDM transmission systems.Finally,to further address the problem that a single PTS algorithm under ultra-large carrier and ultra-high-order QAM modulation cannot meet the system's PAPR suppression requirements,this paper introduces a clipping algorithm.By analyzing the influence of parameters in the clipping algorithm on the performance of PAPR and BER,based on the analysis results and the processing flow of the proposed L-MCTPFS-PTS algorithm,the clipping scheme of two different strategies combined with L-MCTPFS-PTS pretreatment is proposed.The joint scheme retains the excellent PAPR suppression gain of the clipping algorithm,and greatly improves the BER performance loss caused by the clipping algorithm through the L-MCTPFS-PTS algorithm.Therefore,the joint solution can better meet the requirements of signal PAPR suppression in the future “ultra-large bandwidth and massive throughput” system.