Research On Key Technologies Of 5G New Multicarrier (FBMC)

Orthogonal Frequency Division Multiplexing(OFDM),one of the key technologies of the fourth generation mobile communication system(4G),has excellent performance,and it has been widely used in all kinds of communication systems.However,OFDM technology has many disadvantages.The use of a rectangular filter brings a high out-band leakage.The introduction of Cyclic Prefix(CP)results in a reduction in spectral efficiency,and the receiver demodulation at the OFDM system requires the subcarriers to maintain orthogonality.Therefore,in the fifth generation mobile communication system(5G),the research of new multi-carrier technologies has become the focus of many researchers.For the use of a new type of prototype filter with good time-frequency domain focusing,Filter Bank Multi Carrier(FBMC)technology is considered as a suitable solution for as may replace OFDM technology transmitting 5G multi-carrier.The FBMC system has very low out-of-band emissions by using a well-performed prototype filter,while eliminating the need for a cyclic prefix as a guard interval and improving the spectral efficiency of the system.In addition,the FBMC system has strong Inter Carrier Interference(ICI)and Inter Symbol Interference(ISI)capability.In the research of FBMC technology,the basic principle and technical characteristics of multi-carrier modulation system represented by OFDM system are studied firstly,and the research work of the current 5G new multi-carrier technology is discussed.Aiming at the multi-carrier modulation system of filter bank,the basic principle and characteristics of FBMC technology are analyzed in detail,and three commonly used FBMC implementation methods are introduced.Aiming at the prototype filter design problem of FBMC system,the design methods of prototype filter in FBMC system are studied,including frequency sampling technique,windowing technique and direct optimization of filter coefficient technique,the principle and performance of several prototype filters are studied.In this paper,a new prototype filter is designed by using the direct optimization filter coefficient technique.According to the minimum stop-band energy criterion,the stop-band energy of the prototype filter is minimized,the interference between the carriers and symbols is limited within a range while satisfying the symmetry and Nyquist conditions of the filter design,construct mathematical optimization problem.Prototype filter coefficients are solved by non-linear optimization method to get the designed prototype filter.Simulation results show that the prototype filter designed in this paper has better performance than the reference filter.Aiming at the problem of high Peak-to-Average Power Ratio(PAPR)in FBMC system,the PAPR of multi-carrier system and the methods of reducing PAPR are studied,the realization process and technical characteristics of various methods are analyzed.In order to reduce the PAPR in the FBMC system,an Improved Bilayer Partial Transmission Sequence(IBPTS)algorithm is proposed.Based on the idea of traditional PTS,this algorithm takes into account the overlapping characteristics of FBMC signals and reduces PAPR of the system.By introducing a bilayer structure,the weighted phase factor is limited within a certain range,which reduces the searching complexity of the IBPTS algorithm and has better system performance than the traditional PTS algorithm.