Analysis And Optimization Of F-OFDM System

In order to meet the massive connection requirements of future mobile devices,the fifth generation of mobile communication proposes more stringent requirements for new waveforms,for instance higher spectral resolution,higher bandwidth efficiency,higher flexibility to process multiple kinds of services and so on.In 2015,Hua Wei Company proposed Filtered OFDM(F-OFDM)which is a smooth evolution scheme based on OFDM.It not only inherits the advantages of OFDM,but also shows lower out of band emission and exhibit higher flexibility for parameter configuration.However,the complexity of F-OFDM is high,and each sub-band of the system still needs strict timing and synchronization requirements,which will greatly constrain its application in the next generation of communication networks.Aiming at those problems,this thesis has done a detailed research on F-OFDM system,and the main contributions are shown as follows:1.The basic structure and key performance of F-OFDM are studied.Starting from the basic framework of F-OFDM system,this thesis gives an example with two sub-bands to introduce the signal modulation and demodulation in F-OFDM.Then analyze the sub-carrier mapping and sub-band filter processing methods,and discuss a variety of filters designing methods and their performance indicators in F-OFDM system.Finally,we conclude the main advantages and flaws of F-OFDM system.2.Based on the DFT modulated filter bank,the optimization scheme of F-OFDM system is proposed,named Multiservice-Filter Bank(M-FB).The new scheme utilizes the filtering process for each subcarrier to reduce the out of band emission,relax the timing and synchronization requirements by flexibly choosing the filter with better frequency containment to divide sub-channels.In addition,through using multiphase decomposition,the proposed scheme reduces effectively computation complexity.The theoretical analysis and simulation results prove that compared to F-OFDM,M-FB can achieve the same bandwidth efficiency as F-OFDM,but shows lower implementation complexity,and exhibits a better bit error rate and higher anti-carrier frequency offset capability.Furthermore,the proposed M-FB can use discontinuous spectrum,displays more flexibility than F-OFDM system.3.Aiming at the problem of the decreasing system performance because of inter-carrier interference,based on the biorthogonal filter banks theory,the Even-Odd M-FB scheme is proposed to process odd and even sub-carrier respectively by using orthogonal filter pair.Deduce the orthogonal relationship between the filter pair used on the odd and even subcarrier,and gives the designing method of the filter.The simulation results show that Even-Odd M-FB system has better anti-interference ability and lower inter-carrier interference level compared with M-FB.Besides,the bit error rate and mean square error will exhibit different in M-FB because of different parameters,such as filter,roll off factor and sub-channel number.In addition,the proposed Even-Odd M-FB scheme also has some shortcomings,such as larger out-of-band emission than M-FB,and its peak-to-average ratio is as high as M-FB and OFDM.