Research Of Multi-carrier Modulation System Based On Biorthogonal Filter Bank

The fourth generation of mobile communication system has been very mature,the potential of the modulation technology used has been exhausted,has been unable to cope with the new challenges brought by new business such as large-scale machine communication,Internet of Things,Car Networking,Smart City.In order to meet the explosive mobile data transmission needs of the era of the future,many 5G multi-carrier alternatives have been put forward one after another.Compared with other multi-carrier modulation schemes based on symmetrical structure,the unique biorthogonal characteristic of Biorthogonal Frequency Division Multiple Access(BFDMA)makes the synthesis end make up for the signal distortion caused by the undesired spectral characteristics of the filters at the analysis end,System reconstruction accuracy is higher.This article focuses on BFDMA system design and its sparse improvement program made some work:1.Prototype filter is an important factor that affects the performance of BFDMA system.In this paper,the prototype filter of BFDMA system is designed by RRC method.Taking the bit error rate(BER)and the available bit rate(ABR)performance as the evaluation indexes,the prototype filters designed with different roll-off factors are optimized.The RRC filter with a roll-off factor of 0.2 is selected as the prototype filter of the BFDMA system.2.In order to evaluate the system performance of BFDMA in an objective and fair manner,this paper utilizes Orthogonal Frequency Division Multipling(OFDM)and Filtered Multi-tone(FMT)as the comparing objects,from four aspects: BER,ABR,out-of-band leakage and frequency offset.The simulation results show that BFDMA is a multi-carrier scheme with satisfactory performance.3.Aiming at the problem that the computation of the BFDMA filtering process is large,this paper proposes its improved solution,Sparse-BFDMA.Its core idea is to reduce the computational complexity of the filtering process by sparsifying the prototype filter.The simulation comparison of BFDMA and Sparse-BFDMA with different sparsity shows that Sparse-BFDMA can achieve the mutual replacement between system performance and computation by adjusting sparsity.In addition,inorder to improve the targeting of the original sparsification algorithm,an improved algorithm is proposed in this paper.A pre-optimization stage is added.By examining the influence of the filter coefficients on the overall frequency response,the filter coefficients to be optimized are reduced.In this way,the specificity of the algorithm is improved.Simulation results show that under the same error margin,the sparsity of the filter designed by the improved algorithm is 3.3% higher than that of the original one.