Waveform Design Of Filter Bank Multi-carrier System

With the vigorous development of big data and the Internet of Things,the amount of information contained in the communication system increases explosively.The advent of 5G puts forward higher requirements for communication quality.However,the 4G wireless communication technology with orthogonal frequency division multiplexing technology as the core has been unable to meet the needs of emerging business scenarios,so researchers propose to use new multi-carrier technology to replace it.Filter bank multi-carrier(FBMC)has attracted much attention due to its low out of band leakage and high frequency spectrum utilization.In FBMC system,the prototype filter is the key to affect the system performance.The special design of prototype filter can make the performance more superior.At the same time,FIR filter is the key component in digital signal processing,and its optimal design can effectively improve the system performance.Therefore,it is feasible to design FIR filter and apply it as prototype filter in FBMC system.In view of the above ideas,this thesis studies the application effect of FIR filter by unconstrained optimization design and constrained optimization design as prototype filter in FBMC system.This thesis first introduces the FBMC system,the prototype filter,and the design of FIR filter.Besides,we derive a variety of signal to noise and interference ratio(SINR)models related to filter coefficients directly,and determine their accuracy and application value.Then,the SINR model is further transformed into a bit error rate(BER)model.Taking the average BER at each time of the sub-carrier as the cost function,this thesis uses the unconstrained gradient optimization method to optimize LPFF and NLPFF with two types of structures.The optimization result can only be NLPFF whose SINR(BER)results were tested,and compared with the results of PHYDYAS filter in AWGN and CFO cases.The simulation results show that the SINR(BER)results of the specially designed prototype filter can be approximately or even better than that of the PHYDYAS filter under the premise of better stop-band performance,or the SINR(BER)result of the specially designed prototype filter can be greatly improved without considering the filter performance.Finally,in order to improve the comprehensive performance of the filter in the FBMC system and realize the precise control of performance,this thesis proposes to add the ambiguity function or SINR(BER)as the constraint condition to the FIR filter constrained optimization model to realize the optimization design of the special prototype filter for the FBMC system.The method of adding ambiguity function constraint is to express the ambiguity function into two kinds of constraint conditions according to its position relationship,and combined with the design method of SR-NYQ filter.The pass-band and stop-band error energy and ambiguity function are weighted to establish the iterative optimization design model.In addition,this thesis proposes to combine the SINR(BER)constraint condition with the multi-index exchange constraint condition to obtain the new multi-index optimization model,the prototype filter is optimized by adjusting the pass-band fluctuation,stop-band attenuation and length of transition band.These two methods can achieve the mutual conversion that the system performance can be improved by optimizing the prototype filter.The type II LPFF processed as the prototype filter of FBMC system can achieve the SINR(BER)results better than the PHYDYAS filter,and has better stop-band attenuation and narrower transition band.