Principle And Application Of Generalized Frequency Division Multiplexing

Generalized Frequency Division Multiplexing(GFDM)is a multi-carrier modulation technology based on Orthogonal Frequency Division Multiplexing(OFDM)technology combined with filter banks.It also has flexible data block structure on the premise of retaining most of the advantages of the OFDM system.high spectral efficiency,low OOB,low PAPR and other advantages,can meet many needs of wireless communication.For the purpose of further enhance the capability of the GFDM system,to research the synchronization and the channel estimation is extremely significant.In this essay,several multi-carrier waveforms are briefly introduced and the synchronization and channel estimation of GFDM systems are studied.The major details of the essay include:Firstly,the system philosophy of GFDM is investigated concretely,and the capability of OFDM and GFDM is emulated and juxtaposed.Three other multi-carrier waveforms are introduced: FBMC,UFMC,F-OFDM,and their system principles are studied and analyzed.Examination of the emulation results demonstrates that the GFDM system enhances the spectrum utilization besides that declines the out-of-band power leakage,so that the GFDM system can adapt to the air interface requirements of 5G application scenarios.Secondly,the synchronization technology of GFDM system is studied.The impression of synchronization deviation on GFDM system is emulated.The classical GFDM synchronization algorithms based on independent preamble and embedded preamble are deeply studied,and it is found that the performance of the former is better than that of the latter.On this basis,an improved synchronization algorithm based on independent preamble is proposed.Using the good correlation characteristics of CAZAC sequence,a preamble structure with conjugate symmetry and two-segment repetition is constructed,and then the delay correlation algorithm is used to realize the coarse frequency offset Then use the M-segment correlation method to estimate and compensate the fine frequency offset.It can be seen from the simulation results that the design of the preamble solves the "flat top effect" problem,reduces the secondary peak interference problem in the multipath channel,and reduces the complexity of the receiving end;it can also be affected by a large frequency offset.Accurately perform frequency offset estimation and compensation.Finally,the channel estimation technique of GFDM system is studied.Three traditional pilot structures of discrete,block and comb are analyzed,and two pilot interference elimination algorithms are deeply studied: Pilot-IC algorithm and Tx-IC algorithm.After simulation,it is found that these two algorithms are suitable for flat fading channels.And the capability of Tx-IC algorithm is superior to Pilot-IC algorithm.In viewed of the Tx-IC algorithm,an enhanced scheme is put forward in this essay.First,a new pilot composition is constructed,and the precoding operation in the Tx-IC algorithm is performed at the receiving end.Finally,the improved OMP algorithm is used for reconstruct the channel.The emulation consequences demonstrate that thecapability of this scheme is obviously preferable to the LS algorithm,in addition the amount of calculation is below the MMSE algorithm,which is easier to implement.