Research On Peak-to-average Power Ratio Reduction Technique For Cognitive NC-OFDM Systems

With the rapid spread of wireless communication services,the scarcity of wireless spectrum resources has become increasingly apparent.How to effectively use limited spectrum resources has become an urgent problem to be solved.Cognitive radios can intelligently perceive frequency bands that are not occupied by authorized users in the wireless environment for use by unauthorized users,thereby greatly improving the utilization of spectrum resources.Non-Continuous Orthogonal Frequency Division Multiplexing(NC-OFDM)is the best implementation of the physical layer of a cognitive radio system by sensing the spectrum and enabling the free closing and allocation of subcarriers.This paper focuses on the peak-toaverage ratio reduction techniques of cognitive NC-OFDM systems.The main research work includes:1.Researched the cognitive NC-OFDM system model and technical advantages,theoretically analyzed the PAPR probability statistical characteristics of cognitive NC-OFDM systems and compared traditional PAPR reduction algorithms such as signal predistortion,coding classes,and probabilities.This article also conducted a simulation experiment analysis.2.Aiming at reducing the poor PAPR performance of traditional PTS algorithm,an improved interleaving and segmentation PTS algorithm is proposed.This algorithm reduces the system subcarrier sequence by performing random segmentation on the basis of input frequency domain data interleaving packets.The relevance.The simulation results show that the algorithm can reduce the PAPR of the system more effectively and its computational complexity is also improved.3.Aiming at the problem of slow convergence of traditional ACE algorithm,an ACE-PTS algorithm based on pre-expansion is proposed.The algorithm uses a weighting factor to pre-extend the constellation points,thereby reducing the number of iterations of the constellation points and ensuring that the constellation points are mapped into an extensible area.The simulation results show that the pre-expanded ACE-PTS algorithm can effectively reduce the PAPR effect of the system,and its computational complexity will not increase.