Research On Synchronization Technology Of Multicarrier Communication System Based On Filter Bank

As a kind of multi-carrier communication system based on filter bank,FBMC has the advantages of low spectrum sidelobe and low out-of-band leakage.FBMC system using a separately designed prototype filter can achieve higher spectrum utilization than OFDM system.In the near future,with the in-depth study of low-complexity implementation of FBMC system and further development of hardware technology,the large-scale application of FBMC system becomes possible.In 5G or future communications,it will play an increasingly important role,and is expected to become an alternative to OFDM,adapting to more diverse application scenarios.However,like OFDM system,it still has a high sensitivity to timing and frequency deviation,and the quality of the synchronization algorithm will directly affect the performance of FBMC system.This paper studies the timing synchronization and carrier synchronization of FBMC system.Generally,in OFDM systems and FBMC systems,in order to ensure better synchronization performance,data-aided synchronization methods are often used,and the key to the data-aided synchronization method is to design a synchronization sequence with a special structure.For this reason,the synchronization sequence structure of several classic algorithms such as S&C,Minn of the OFDM system and TR1,TR2,MLS of the FBMC system is studied,and the performance of the measurement functions of these algorithms is analyzed.Then,based on the design ideas of these algorithms,a timing synchronization method that directly correlates the received signal with the local sequence is studied,and the influence of noise and frequency offset on the system timing synchronization performance is analyzed when using synchronization sequences with opposite,symmetric and conjugate structures.Finally,on the basis of summarizing the advantages and disadvantages of these different synchronization structures,a synchronization sequence with a phase-weighted conjugate symmetric structure is designed.It takes advantage of the strong anti-frequency offset capability of the conjugate symmetric structure,and at the same time introduces the design of the weight sequence,so that the system has a high timing accuracy even at a low signal-to-noise ratio.Simulation results show that under the goal of achieving 100% timing accuracy,the system using phase-weighted conjugate symmetric structure requires 3d B lower signal-to-noise ratio than the system using conjugate symmetric structure,which fully reflects the advantages of the weight sequence.For the carrier synchronization of the FBMC system,several classic algorithms of OFDM system and FBMC system that use the accumulated phase difference of the frequency offset to estimate the frequency offset are analyzed.Then,using this principle and combining the synchronization sequence of the phase-weighted conjugate symmetric structure,the estimation of the integer and fractional parts of the carrier frequency offset is given,and a small MSE is achieved.Finally,for the residual frequency difference and phase difference,this paper designs a method to estimate the phase offset using the comb pilot in each FBMC symbol.Simulation results show that the system after the frequency offset and phase offset compensation can achieve the same BER performance as that without frequency offset and phase offset.This shows that the proposed methods can well realize the carrier synchronization of the FBMC system.