Research On Peak-to-Average Ratio Suppression Technology In O-OFDM System

As the digital signal processing technologies developed,the Orthogonal Frequency Division Multiplexing(OFDM)technology is widely applied in wireless communication.Thus,the large capacity,high-speed and low cost optical OFDM(O-OFDM)translation system is constructed with the technology in visible light communication.The MATLAB software is used to build the system simulation platform.Based on this,the performance of OFDM and O-OFDM systems is analyzed.Through calculation and analysis,both systems have a high Peak-to-Average Ratio(PAPR).In response to this problem,various PAPR suppression schemes have been proposed.Firstly,a new orthogonal of Polar Orthogonal Frequency Division Multiplexing(P-OFDM)method is proposed for the high PAPR problem.The idea of polar coordinate conversion and the transform of compassion extending are combined in this method.Trough simulation and calculation,the results show that the new method has better PAPR performance which is nearly 8dB better than asymmetrically clipped optical OFDM system,and about 1dB better than direct current biased OFDM system.At the same time,the Hermitian conjugate symmetry is not satisfied in the input signal during the polar coordinate conversion process.So using this method can effectively reduce the PAPR value of the system,decrease the nonlinear distortion of the system,and improve the performance of the system.Spectrum utilization and error performance are also improved over traditional O-OFDM systems.Secondly,using the idea of Selected Mapping(SLM)method and combining the advantages of Discrete Cosine Transform(DCT)transform and Inverse Fast Fourier Transform(IFFT)transform linearity,an improved SLM peak-to-average ratio suppression scheme—DCT-ISLM method is proposed for the disadvantages of high PAPR and high computational complexity in O-OFDM systems.Through simulation,the result shows that compared with the conventional SLM method,the proposed DCT-ISLM method reduces the peak-to-average ratio by about 3.5dB.With the increasing of the number of candidate signals,the complexity of the system is effectively improved.At the same time,the scheme is applied to the traditional O-OFDM visible light communication system,and the error performance is also better than the conventional SLM scheme,thereby further enhancing the practical value of this scheme.Finally,two DCT-ISLM methods based on polar coordinate transformation are proposed with the advantages of the DCT-ISLM and P-OFDM methods for improving the performance of the system.The simulation results show that two methods all have better PAPR performance than the traditional ones,and the PAPR performance of the improved DCT-ISLM method based on polar coordinate transformation(PDCT-ISLM)is the best.Compared with the P-OFDM method,the PAPR value is also reduced by 0.4 dB.At thesame time,compared with the C-SLM method,the spectrum utilization and computational complexity are effectively improved under the condition of basically the same error performance.