Research On F-OFDM For The Next-generation Wireless Communication Systems

The 5th generation(5G)mobile communication system needs to support more different application scenarios,which brings forward higher requests to the wireless access capability of the system.Filtered Orthogonal Frequency Division Multiplexing(F-OFDM)is a new air-interface multi-carrier waveform modulation technology for 5G,which is proposed by Huawei Corporation.In F-OFDM,the system bandwidth is divided into multiple subbands by subband filter banks,and each subband can be configured different waveform parameters flexibly according to the practical application scenarios.F-OFDM not only keeps all the advantages of OFDM,but also overcomes the disadvantages of highly out of band emission,inflexible waveform parameter configuration and poor performance of asynchronous signal transmission.As a new technology,F-OFDM is necessary to have a low design complexity,good anti-interference ability and high time-frequency resource utilization,so that it will be adopted by 5G standardand realized commercialization.This thesisemphatically studies the design of subband filter banks,the configuration of waveform parameters and asynchronous signal transmission,and putsforward a design scheme with good comprehensive performance.The main research contents of this thesis are as follows:1.The design of subband filter banks influences directlythe complexity of F-OFDM implementation,out of band emission suppression and the capability of asynchronous signal transmission.On the basis of the hanning window,the prototype filter is designed by adopting the principle of window function soft truncation,and subband subcarrier mapping algorithm is proposed to improve the design method of cosine modulation filter bank in this thesis,so that achieving the design of subband filter bank with low complexity in F-OFDM.At the same time,the frequency domain filtering operation of the subband signal is carried out by using the overlapsave method with low calculating complexity.Compared with OFDM,it is obvious that the designed subband filter banks can not only ensure the good performance of anti-interference,but also can support the signal transmission on the condition of high order modulation.2.Aiming at the reduction of signal transmission quality caused by tailing phenomenon in narrow subband filter operation,and the problem of multipath channeltransmission,the effect of cyclic prefix(CP)length on the anti jamming ability of F-OFDM was studied,and a design scheme of CP length is proposed when the subband width is less than 720 KHz in this thesis.The simulation results show that the CP length can effectively reduce the interference caused by multipath channel transmission and eliminate the interference caused by the smearing in sub band filter operation.3.F-OFDM uses filters to limit the out of band emission of each subband,but it can not guarantee no interference between the subbands.A design scheme which inserting the guard subcarrier into the passband of subband filters is proposed in this thesis.Simulation results show that the proposed design scheme not only hasa good performance of anti-interference and spectrum utilization efficiency,but also has the ability to keep time-frequency resource grid maintain the conventional design and the filter design unaffected by the change of application.4.On the basis of subband filter banks design,this thesis combines the CP length and the guard subcarrierto analyze the F-OFDM in high-speed mobile scene and different modulation modes,the results show that the designed subband filter banks and waveform parameters can meet the requirement ofF-OFDM with good asynchronous signal transmission capability.