Research On Pilot-based Channel Estimation For FBMC System

Filter Bank based Multi-Carrier/Offset Quadrature Amplitude Modulation(FBMC/OQAIM)technology scheme due to the outstanding advantages of low sidelobe leakage in the spectrum and does not require a cyclic prefixes(high spectral efficiency),the receiving end does not require strict orthogonal synchronization.In terms of the 5G physical layer,it has become an alternative technical solution that can replace Orthogonal Frequ,ency Division Multiplexing(OFDIVM)technology in the future.However,due to the adoption of the GQAM modulation scheme in the FBMC system,the system only satisfies the orthogonality of the subcarriers in the real domain.Therefore,there is still inherent interference in the imaginary field,so that some classical techniques commonly used in OFDM systems cannot be directly applied in FBMC systems.Especially in the channel estimation of the FBMC system still faces some challenges.The main research work of the article includes:(1)Analyze and discuss 4 non-orthogonal multi-carrier transmission technologies tor 5G.The theoretical basis and system implementation of OFDM,FBMC,Generalized Frequency Division Multiplexing(GFDIVM)and Universal Filtered Multi-Carrier(UFMC)are introduced.The basic principles of the FBMC system are studied,including Prototype filter design,system implementation framework,and OQAM modulation characteristics;the performance of tme FBMC system and the OFDM system is compared through simulation,and the performance and advantages of the other two notn-orthogonal multi-carrier transmission technologies are compared.(2)The channel estimation method of the traditional OFDM system in the frequency domain is studied.The OFDM system modulation principle,characteristics and insertion method of cyclic prefix are analyzed.The performance of various aspects of OFDM system is ansalyzed through spcific Matlab simulation;the traditional channel estimation method in OFDM system under the condition of block pilot structure is studied:Least Square(LS),Minimum Mean Square Error Method(MMSE),Linear Minimum Mean Square Error(LMMSE)method,and Singular Value Decomposition Method,SVD),and through the Matlab simulation analysis of the estimated characteristics of these types of methods.(3)The pilot structure algorithm based on interference approximation method(IAM)in FBMC system is researched.Focused on the imaginary interference problem of the FBMC/OQAM system,and the IAM pilot structure is improved.Based on IAM pilot structure,an iterative algorithm for IAM preamble estimation in FBMC/OQAM system is studied.The algorithm uses a new three-column pilot structure,and at the same time,it uses multiple iterations to obtain more accurate channel information,reconstructed the inter-symbol and inter-subcarrier interference,thereby improving the channel estimation performance.