PAPR Reduction Optimization Schemes For O-OFDM System

In recent years,with the limit of spectrum resource and increase in the communication rate,higher demands for spectrum efficiency and communication capacity have been proposed.Optical Orthogonal Frequency Division Multiplexing(O-OFDM)technology has the advantages of strong resistance to multipath fading,strong resistance to inter symbol interference,and high spectrum efficiency,it is becoming one of the effective method of getting higher spectrum efficiency and communication capacity.However,O-OFDM system has high peak to average power ratio(PAPR),which is the obstacle of the communication system performance and further development,researching novel PAPR suppression technology has become a research hotspot at home and overseas.This thesis deeply researches the PAPR suppression schemes in OOFDM system,proposed a curve fitting threshold active constellation extension(ACE)and dynamic clipping scheme,a scheme based on Hadamard sequence and genetic algorithm selective mapping(SLM),a scheme based on repetition code and genetic algorithm SLM,a scheme based on selecting preferred phase weighting factor and low block partial transmit sequence(PTS),a combined segmental compand scheme,and the schemes are optimized for reducing computational complexity,reducing side information,and reducing bit error rate(BER)based on PAPR suppression.The main research works of this thesis are as follows:1.Focusing on the problem of regular threshold of the ACE scheme,the higher risk of peak regeneration,PAPR suppression performance is limited and the clipping causes the signal distortion and the spectrum leakage,a PAPR suppression scheme based on curve fitting threshold ACE and dynamic clipping(CFT-ACE-DC)is proposed.Focusing on the problem of the regular threshold in ACE,using curve fitting threshold ACE(CFT-ACE)to find the preferred threshold value,by pre-setting a small number of threshold values and simulation,fits a curve of the relationship between threshold values and PAPR values based on the simulation results,and selects the preferred threshold values.In addition,the PAPR is further suppressed by dynamic clipping(DC)the signal after ACE,and the OFDM signal with excessive amplitude after the constellation extension scheme is suppressed,and the threshold value is controlled by counting the number of OFDM signals that exceed the threshold.The simulation results that the proposed CFT-ACE-DC scheme has significant PAPR suppression performance compared with conventional ACE and CFT-ACE,the CFTACE-DC scheme can suppress 5.91dB of PAPR compared with the original OFDM scheme when the complementary cumulative distribution function(CCDF)is 10-3,and has the advantage in BER performance.2.Focusing on the problem of large amount of side information of the SLM,a scheme based on Hadamard sequence and genetic algorithm SLM and a scheme based on repetition code and genetic algorithm SLM are proposed.The proposed Genetic Algorithm Hadamard SLM(GA-HSLM)scheme uses Hadamard sequence as the pre-defined partial phase weighting sequence,which can significantly reduce the amount of side information because of the uniqueness feature of Hadamard sequence.Compared with the conventional SLM(C-SLM),simulation results that the GA-HSLM scheme has significant PAPR suppression performance and side information performance.A scheme based on Genetic Algorithm and repetition code as the preset partial phase weighting sequence SLM(GARCSLM)transmits the repetition code as the side information and makes error correction on part of the OFDM signal at the receiver.Compared with the C-SLM,simulation results that the proposed GA-HSLM scheme has significant PAPR suppression performance and side information performance,and the GA-RCSLM has the advantage in BER performance.3.Focusing on the problem of the PAPR suppression performance is limited in low number of blocks of the PTS,a scheme based on selecting preferred phase weighting factor and low block PTS(SP-PTS)is proposed.This scheme has higher flexibility by fixing the weighting factor of the first block and obtaining the weighting factor of the second block by iteration.Simulation results that the SP-PTS scheme has higher flexibility and better PAPR suppression performance.4.Focusing on the problem of severe signal distortion and high computational complexity of the nonlinear compand,a combined segmental compand scheme is proposed,which achieves a compromise between computational complexity and signal distortion.Finally,a joint scheme based on the SP-PTS and combined segmental compand scheme is proposed,which combines the advantages of the non-distortion PTS scheme and the significant PAPR suppression performance of the compand scheme.Simulation results that the proposed combined segmental compand scheme has low computational complexity,the joint scheme can further suppress PAPR,the BER performance is better than the combined segmental compand scheme and μ-law compand scheme(μ=2)under the condition that the average power of OFDM signal is basically unchanged.