PAPR Optimization Schemes For O-OFDM System

With the rapid development of the Internet and audio and video services,high requirements are placed on the capacity and speed of the communication system.Orthogonal frequency division multiplexing(OFDM)technology has the advantages of high spectrum efficiency,high transmission rate,and strong anti-dispersion ability.OFDM has been applied in many fields.Therefore,opti-cal orthogonal frequency division multiplexing(O-OFDM)system has become a research hotspot in the field of optical fiber communication.The peak to average power ratio(PAPR)problem in the O-OFDM system is hindering its further application and development.High PAPR will cause the signal to exceed the linear operating range of the hardware,and then cause the signal distortion and the increasement of bit error rate(BER)and hardware loss speed.Aiming at the PAPR problem in the O-OFDM system,this thesis deeply researches PAPR suppression schemes in the O-OFDM system based on clipping,discrete Hartley transform precoding(DHT Precoding,DHTP),selective mapping(SLM)and partial transmit sequence(PTS)technology,and proposes several optimization schemes,so as to achieve a compromise between PAPR suppression performance,BER performance,computational complexity,and additional transmitted sideband information.The main research contents of this thesis are as follows:1.Aiming at the problem of severe signal distortion of clipping technol-ogy and high computational complexity of iterative clipping filtering technol-ogy,a PAPR suppression scheme based on DHTP and Clipping-Filtering Algo-rithm(DHTP-CFA)is proposed.Based on the research of DHTP-CFA,a PAPR suppression scheme based on adaptive clipping algorithm and DHT precoding(ACA-DHTP)is proposed so as to solve the problem that the clipping threshold cannot be flexibly set.This solution counts the number of clippings in the itera-tive process,and adaptively adjusts the clipping threshold based on parameters such as high water level and low water level,so as to improve the problems caused by too high or too low clipping threshold.The simulation studies PAPR suppression performance and BER performance,and numerically analyzes the computational complexity.The simulation results show that the ACA-DHTP scheme has significant advantages in PAPR suppression and BER performance compared with multiple PAPR suppression schemes.The numerical analysis re-sults show that the additional computational complexity of the scheme is lower compared with that of the inverse fast Fourier transform(IFFT).2.Aiming at the high computational complexity of SLM technology,a sorting and filtering-based SLM(SF-SLM)scheme is proposed.This scheme generates three groups of OFDM candidate signals by applying screening rules to OFDM candidate signals,and selects the group with the smallest PAPR for transmission.The simulation studies PAPR suppression performance and BER performance,and numerically analyzes the computational complexity and ad-ditional transmitted sideband information.The simulation results show that the SF-SLM scheme has significant PAPR suppression performance and BER per-formance advantages compared with the conventional SLM(C-SLM)scheme.Numerical analysis shows that the SF-SLM scheme greatly reduces the com-putational complexity when generating the same number of OFDM candidate signals.As the number of generated OFDM candidate signals continues to in-crease,the computational complexity reduction ratio(CCRR)of the SF-SLM scheme will continue to increase compared with the C-SLM scheme.The side-band information that needs to be additionally transmitted is the same as the C-SLM scheme.3.PTS technology is a probabilistic PAPR suppression technology with high computational complexity.Random segmentation is a segmentation method with good PAPR suppression performance,but it has problems such as high computational complexity and additional transmission of sideband informa-tion.To solve the above problems,a PTS scheme based on improved seg-mentation(IS-PTS)is proposed.This scheme combines interleaving division and random division,applying different division methods to different parts of OFDM subcarriers.The simulation studies PAPR suppression performance and BER performance,and numerically analyzes the computational complexity and additional transmitted sideband information.The results show that under the premise of reducing computational complexity and sideband information,the IS-PTS scheme has similar PAPR suppression performance and BER perfor-mance to random segmentation.