Performance Analysis And Optimization Of Filtered Multi-tone Modulation System

The rapid development of the mobile Internet and Internet of Things has gradually exceeded the current carrying capacity of 4G,and the fifth generation mobile communication system(5G)pursues the ultimate user experience.A more stringent requirement on the frequency band efficiency and spectral flexibility of the physical layer is put forward.As a multicarrier modulation technique based on filter banks,Filtered MultiTone(FMT)uses the filter banks to limit the bandwidth of each subchannel,so that the spectrum of each subchannel has better resolution and constraint.Therefore,the frequency offset can be effectively avoided,and the orthogonality in the actual channel transmission is not easy to be destroyed,so as to effectively alleviate some inherent problems of the 4G physical layer core technology orthogonal frequency division multiplexing(OFDM),for instance,the strict requirements of symbol timing and carrier synchronization,the need to insert the cyclic prefix and frequency offset sensitivity and so on.However,this feature of FMT system has also limited its spectral efficiency,and the factors of its performance need to be further studied and evaluated.To solve these problems,this thesis analyzes and optimizes the performance of FMT modulation system,and the specific contents and results are as follows:1.The structure and performance of FMT modulation system are analyzed.Firstly,the design of prototype filter in the filter banks of FMT system,the length of the polyphase components,the extractor/ interpolator and the number of subcarrier are analyzed and simulated to determine the main factors that affect the performance of the system.Then,the LTE link level simulation analysis of FMT system is carried out.Taking OFDM as the reference object,the advantages and disadvantages of the FMT modulation system are analyzed from three aspects: the complexity of system,the ability of anti-frequency offset and the spectral efficiency.The results show that the performance of FMT system depends on the design of the prototype filter in the filter bank;compared with OFDM,FMT modulation has better transmission stability,efficiency and anti frequency offset capability,but its spectral efficiency needs to be further improved.2.The optimal design of filter bank in FMT modulation system is studied.In order to improve the subchannel spectrum constraint of FMT system and improve the performance of the system,an optimal design method of filter banks based on inter-carrier interference suppression is proposed.The subchannel spectrum constraint is improved by optimizing the passband cutoff frequency of the prototype filter,the bandwidth of t he transition band and the peak of the sidelobe,and the design of the prototype filter can be more flexible.Simulation results show that the prototype filter designed by this optimization method has better spectral constraint,which can make the FMT system get better subband partition performance.3.The spectrum efficiency optimization of FMT modulation system is investigated.To solve the problem of low spectrum efficiency in FMT system,a spectrum efficiency optimization scheme for FMT system is proposed(O-FMT).The scheme is based on polyphase decomposition of FMT filter bank,and the spectrum efficiency of FMT system is improved by controlling the design requirements of the polyphase filter bank and introducing the overlapping in the frequency spectrum.Firstly,the implementation structure of O-FMT system is deduced theoretically;then,the spectral characteristics,the symbol error rate,the inter-carrier interference and the spectral efficiency of the O-FMT system are simulated and analyzed respectively.The results show that O-FMT can significantly improve the spectral efficiency of FMT system,and can also choose different overlapping factors according to actual needs,and construct the transmission waveforms with different parameters.