Research On Peak-to-Average Ratio Optimization Based On An Advanced PTS Method In NC-OFDM System

With the demand for wireless communication continues to grow,how to use spectrum resources more efficiently is an important issue that needs to be solved in future wireless communication systems.Cognitive Radio(CR)technology can find unused spectrum usage in the spectrum pool,avoiding the impact on authorized users and improving the utilization of spectrum resources.The data transmission technology of the CR physical layer is most commonly used by orthogonal frequency division multiplexing(OFDM)technology.The discontinuous orthogonal frequency division multiplexing(NC-OFDM)technology is based on the OFDM technology subcarrier discontinuity which collects the spectrum.The spectrum information that is idle in the pool is used to efficiently transmit data on the subcarriers corresponding to the idle spectrum.However,how to reduce the high peak-to-average ratio(PAPR)problem in NC-OFDM systems still needs to be solved.The existing partial transmission sequence(PTS)method can effectively reduce the high PAPR in NC-OFDM systems.This thesis proposed a PAPR optimization scheme based on the PTS method.Firstly,aiming at the problem of large computational complexity in the traditional PTS method structure,the structure of the PTS method was improved.In the conventional method,the transmitted signal is first subjected to an inverse fast Fourier transform(IFFT)operation operation and then weighted and summed with an optimal twiddle factor.Since the optimal twiddle factor is a constant vector,the transmission signal and the optimal twiddle factor can be weighted and summed before the IFFT operation.Secondly,based on the improved PTS structure,a new segmentation method is proposed.The traditional PTS method can not meet the two performance indicators of PAPR improvement and system complexity reduction at the same time.The improved segmentation method combines two segmentation methods,and adopts the best random PAPR performance in some sub-blocks.The segmentation method adopts the interleaving segmentation method with the lowest computational complexity in another partial sub-block.Finally,before the segmented PTS sub-block is multiplied by the optimal twiddle factor,the iterative search method is used instead of the traditional traversal search method.The iterative search no longer needs to perform repeated search on the twiddle factor,which solves the complicated calculation of the traditional traversal method.Too high a problem.The experimental results show that the improved PTS scheme proposed in this paper can not only effectively suppress the high PAPR of NC-OFDM system,but also reduce the computational complexity of the system,and also help improve the improved PTS scheme.The bit error rate of the system has a good effect on improving system performance.