Study On Channel Estimation For FBMC Systems

Due to introduction of the prototype filter featuring good time-frequency localisation characteristics,the filter bank multicarrier with offset quadrature amplitude modulation(OQAM/FBMC)have a lower out-of-band leakage and an enhanced robustness to relaxed synchronization as compared to the traditional ortohogonal frequency division multiplexing(OFDM)system.As one of the most prominent schemes in the multiple carrier modulation(MCM),it has been widely used in wireless LANs,power line and optical communications.However,OQAM/FBMC sacrifices the orthogonality among subcarriers and only establishes the orthogonality in real domain through OQAM.Therefore,even without any channel fading,noise or synchronization error,there will always be inter-carrier interference(ICI)and inter-symbol interference(ISI)in the received signal,which represent as the intrinsic imaginary interference.In addition,under time selective fast fading channel,the intrinsic interference will become more complex,and limits the pilot interval in time domain.Based on these reasons,the traditional OFDM channel estimation methods cannot be directly applied in OQAM/FBMC,and the channel estimation is the difficult focus in OQAM/FBMC system design.Considering the effect of interference in OQAM/FBMC system,the dual dependent pilots with fast fourier transformation(DDP with FFT)is proposed to solve the problem of excessive pilot power overhead caused by existing OQAM/FBMC channel estimation algorithm under flat channel conditions.Based on the dual-pilot channel estimation(DDP),this algorithm reduced the power of the transmission pilot pairs by introducing phase ambiguity actively,and then estimates the phase ambiguity by utilizing the characteristics of multipath channel energy to guaranteeing the accuracy of channel estimation.Theoretical analysis and simulation results show that the proposed optimization algorithm can effectively improve power efficiency and achieve highly accurate channel estimation performance.In order to solve the problem of the limited pilot density and the complex intrinsic interference in fast fading channel,an optimization scheme based on interference correction is proposed.In this scheme,grouping pilot is used to avoid the problem of pilot computing caused by pilot interval in time domain.And the intrinsic interference in fast fading channels is further processed by interference correction at the receiver.Simulation results show that the traditional OQAM/FBMC channel estimation algorithm can significantly improve the performance of channel estimation in fast fading channels even after only one interference correction optimization.