An Iterative Receiver Algorithm In Filtered Multitone Modulation

Recently,with the development of multi-carrier modulation technology,due to its good anti-multipath capability and spectrum utilization,it has received extensive research and attention.The multi-carrier modulation technology is divided into two categories according to the sub-carrier overlap manner.One is represented by Orthogonal Frequency Division Multiplexing(OFDM)that subcarriers are overlapped and orthogonal to each other.It has features such as simple equalization structure.The other type is represented by the filter multitone modulation technique(FMT),which controls the subcarriers to be non-overlapping to obtain orthogonality.Because of the good spectral constraint between the subcarriers,the orthogonality between the subcarriers is not easily damaged,requires low synchronization and no extra overhead.However,due to the non-ideal reconstruction characteristics of the prototype filter,and the inability to insert cyclic prefixes to counter the multipath effect of wireless channel,inter-symbol interference(ISI)in the FMT system is much more severe than in OFDM.The receiver must eliminate the ISI through the equalization technique and improve the system performance.Based on this background,this paper has conducted a deeper research on the fast implementation structure,channel estimation and channel equalization in FMT system.The main work is as follows:1.This paper introduces the basic principles of FMT in detail,and combines the graphs to derive the fast implementation algorithm of FMT based on polyphase filtering and IDFT/DFT transform,and deduces the signal model of FMT under different channel types,which lays a theoretical foundation for follow-up research.2.Based on the FMT equivalent sub-channel model,the application of linear equalizer,nonlinear equalizer and Turbo equalizer in FMT system under precise channel conditions is studied.The formulas for calculating the tap coefficients of various equalizers are deduced in detail with the peak distortion criterion and the minimum mean square error criterion.simulation and comparison of various types of equalizers in Rayleigh multi-path fading channels.3.Aiming at the problem that traditional receiving algorithms based on training sequence channel estimation in FMT systems is inapplicable,an iterative receiving algorithm based on training sequences is proposed.Iteratively eliminates the ISI of training symbols and improves the accuracy of channel estimation;since the above algorithms are based on hard Iterative decision symbols and have performance gains at high signal-to-noise ratios.Therefore,by combining the turbo equalization structure,an iterative soft-information receiving algorithm based on Turbo structure is proposed.There is also a large performance gain in low SNR.The algorithms are simulated and compared in Rayleigh multi-path fading channels.4.Applying the above algorithm to a time-varying channel,a bi-directional iterative receiving algorithm based on block structure is proposed.The time-varying characteristics of the channel are tracked through forward and reverse channel estimation and iterative interference cancellation.Basing on above algorithm,using the estimation value of the data block obtained by each iteration to perform channel estimation and equalization,a bi-directional iterative receiving algorithm using data sub-blocks is proposed,and a better performance gain is obtained.And validating the effectiveness of the algorithm in Rayleigh fading channels.