Research On Joint Algorithm For PAPR Reduction In OFDM Systems

In recent years,with the rapid development of wireless mobile communication technology,people’s demand for the speed and reliability of data exchange and data transmission is also increasing.Orthogonal Frequency Division Multiplexing(OFDM)technology,as a multi-carrier modulation technology,has good spectrum utilization,high transmission rate and excellent resistance to inter-symbol interference,and has been widely used in modern communications.However,the Peak-to-Average Power Ratio(PAPR)is an important factor affecting the further development of OFDM technology.High PAPR value will make OFDM signal leave the linear working area of power amplifier in the transmission process,resulting in the deterioration of communication performance.Based on this,this thesis studies the PAPR suppression algorithm in OFDM system.Firstly,three types of common PAPR suppression technologies in OFDM systems are introduced in detail,including predistortion technology,coding technology and probability technology.And through theoretical analysis and simulation,the advantages and disadvantages of the three technologies are summarized.Secondly,the performance and influencing factors of Selected Mapping(SLM)algorithm are analyzed in detail,and the Wash-Hadamard sequence is selected as the phase sequence to reduce the sideband information transmission.Aiming at the problems of poor performance and high complexity of SLM algorithm,a joint improved SLM-DCT algorithm is proposed by using the energy concentration characteristics of Discrete Cosine Transform(DCT),the linear properties of inverse Fourier transform and clipping technology.Simulation results show that the improved algorithm has better PAPR suppression performance and lower algorithm complexity.Then,the Active Constellation Extension(ACE)method is studied.Aiming at the shortcomings of ACE algorithm,such as slow convergence speed and many iterations,this thesis uses least square estimation to calculate the descent gradient step size,and combines several OFDM symbols into a superframe for unified processing.Then a LS-ACE algorithm based on frame interleaving is proposed,which further improves the performance of the algorithm.Simulation results show that the improved algorithm has faster convergence speed and better PAPR suppression performance.Finally,in OFDM system with more subcarriers and higher-order modulation,the performance of a single PAPR suppression algorithm is limited.This thesis considers combining the improved SLM-DCT algorithm with the LS-ACE algorithm based on frame interleaving.Then three joint algorithms according to different joint methods are proposed.Through the simulation in different environments,the LS-ACE-SLM algorithm has better PAPR suppression performance,and achieves a balance in many aspects.