Research On Key Problems Of FBMC Channel Estimation

Filter Bank Multi-carrier(FBMC)transmission technology is one of the best candidates for the new wave technology of 5G communication physical layer.Compared with the traditional cyclic prefix(CP)based orthogonal frequency division multiplexing technology(OFDM)transmission technology,its biggest characteristic is to use the prototype filter has good time-frequency focusing characteristics to build system,so there's no need to cyclic prefix can achieve good disturbance rejection,and greatly improve the power spectral density,eliminate the transition region,improve the efficiency of the frequency spectrum of the system.The sensitivity of the system to carrier frequency offset(CFO)can also be reduced to some extent.The reason why the multi-carrier technology of filter banks has so many advantages is that it adopts Offset Quadrature Amplitude Modulation(OQAM),which liberates the strict orthogonal restrictions between subcarriers and requires only orthogonal in the real field.However,the data received at the receiving end of an FBMC system will contain inherent interference generated by the system itself.Therefore,the traditional channel estimation method directly used in OFDM system cannot be directly used in FBMC system.In this paper,the inherent interference problem of FBMC system in channel estimation is analyzed and studied in depth.In this paper,the characteristics of FBMC system are firstly studied by means of comparative analysis.Secondly,the core problems involved in FBMC channel estimation and the deficiencies of various existing solutions are deeply studied and analyzed,and the solutions are given in the following chapters.Among the channel estimation methods for FBMC system,two major methods have been studied in depth,namely Interference Approximation Method(IAM)and Interference Cancellation Method(ICM).The analysis results show that the interference approximation scheme further improves the accuracy of channel estimation on the basis of the traditional scheme,but has some problems such as low transmission efficiency and inability to separate multi-order interference.In addition,for interference elimination methods,the biggest advantage is that it can save the extra cost of pilot and improve the transmission efficiency to the greatest extent,and for the interference problem of FBMC/OQAM system itself,the interference can be completely eliminated in theory.However,the technology itself has some problems,such as increased peak average power ratio(PAPR)and high complexity.In fact,the jamming approximation scheme has the best performance for channel estimation,while the jamming elimination scheme can save the spectrum resources to the greatest extent.Both schemes have advantages and disadvantages,but the ideas are independent of each other,so they can be combined with each other.Firstly,aiming at the problems of interference approximation method,a new block pilot design scheme is proposed.The scheme combines the idea of auxiliary elimination,and has the ability to eliminate the second-order and above interference while improving the pseudo pilot power.The simulation results show that the performance of channel estimation can be further improved when the scheme is used.Secondly,two solutions are proposed to solve the problems of the scheme.The first one is to preprocess the transmitted symbols at the transmitter,which can simplify the channel estimation algorithm at the receiver,so that some schemes which can only be applied in theory can be directly used in reality.The second is to solve the problem that the auxiliary power of auxiliary pilot scheme is too high.Combined with the idea of interference utilization,a new solution is proposed.Theoretical analysis and simulation results show that this scheme can not only reduce the auxiliary power,but also further reduce the bit error rate of the system.