Research On The PAPR Reduction Methods In FBMC System

In recent years,filter bank multicarrier(FBMC)has received widespread attention as a new multicarrier modulation technology.FBMC has good time-frequency focusing characteristic and avoids many defects of orthogonal frequency division multiplexing technology.However,high peak to average power ratio(PAPR)is unavoidable due to multicarrier superposition in FBMC.The FBMC system uses non-rectangular filters and offset quadrature amplitude modulation,and its structure is very special.the PAPR can not be effectively suppressed by using traditional reduction methods directly.So,the FBMC system is more complex to solve the PAPR problem.In order to solve the above problems,this thesis has carried out the research on the PAPR reduction method of FBMC system,and the main research contents and results are as follows:Firstly,aiming at the problem of partial transmit sequences algorithm in FBMC with inadaptability and high complexity,an improved partial transmit sequences algorithm based on double-layer optimization is proposed.The algorithm uses double-layer optimization to disperse the signal optimization into two layers.Each layer can reduce PAPR and computational complexity in some ways.The first layer fully considers the overlap characteristics,and only adds the previous overlapping data blocks to the phase factor selection conditions.The influence of the following overlapping data blocks is eliminated to reduce the PAPR,and reduce the number of phase factor sequences to reduce the computational complexity when the phase factor is selected.The second layer groups the optimized data blocks of the first layer,and in order to reduce the computational complexity,only one data block is selected for re-optimization in each group,and since the selected data block has the greatest impact on the peak value,PAPR can be effectively suppressed.The complexity calculation and simulation results indicate that the proposed algorithm can not only effectively reduce PAPR,but also keep the computational complexity at a low level.Secondly,aiming at the Low PAPR FBMC(LP-FBMC)structure based on discrete fourier transform spread method needs to transmit side information while reducing PAPR,causing the problem of lower transmission rate,an optimized structure of LP-FBMC based on the local phase rotation of the constellation symbol sequence is proposed.Since side information is generated from the choice of four versions of signals,this structure uses the special connection between the four versions of signals to reduce the number of phase rotation angles,so that the constellation symbol sequence can use local phase rotation to replace side information,thereby reducing complexity,improving transmission efficiency.And at the receiver,a larger phase estimation range is used to judge the signal to reduce the bit error rate when the signal-to-noise ratio is low.The complexity calculation and simulation results indicate that the proposed structure can not only increase the transmission rate,but also maintain the same PAPR suppression performance,similar computational complexity and bit error rate performance as the LP-FBMC structure.