Construction And Performance Analysis Of NOMA System Based On Multiwavelet Modulation

Since the non-orthogonal multiple access(NOMA)technology can simultaneously provide services to multiple users on the same transmission resources(in time,spectrum,and space,etc.),it can provide a superior spectral efficiency and system capacity to that of the conventional orthogonal multiple access(OMA)technology.NOMA has been widely recognized as a promising solution to future radio-access networks.The conventional NOMA systems usually adopt orthogonal frequency-division multiplexing(OFDM)as the multi-carrier method,but this scheme has two major defects of high peakto-average power ratio(PAPR)and reduced spectrum efficiency due to the indispensable use of cyclic prefix.In order to combat these drawbacks,scalar-wavelet modulation is exploited to the NOMA systems,but the performance of the NOMA system based on wavelet modulation(SW-NOMA)is limited by the fact that wavelet cannot simultaneously satisfy short support,orthogonality,symmetry,and high-order vanishing moments.However,multiwavelet can simultaneously satisfy these properties.Therefore,consider applying multiwavelet to the NOMA system,construct a NOMA system based on multiwavelet modulation and analyze its performance.Based on multiwavelet theory,a novel NOMA system based on multiwavelet modulation has been proposed in this thesis,which can not only further improve the theory and application system of multiwavelet,but also provide theoretical support for the application of multiwavelet modulation in the NOMA system.The main research work completed in this thesis is as follows:1.Research on the wavelet,multiwavelet and multiwavelet packet theories,and analyze the difference between their Mallat algorithms.And focus on the analysis of three generally used multiwavelets,analyze their time-domain and frequency-domain waveforms.By comparing the frequency spectra of these three multiwavelets,the CL4 multiwavelet with the best spectrum orthogonality is selected and adopted for the multiwavelet modulation in this research.2.On the basis of the OFDM-based NOMA system(OFDM-NOMA)and the scalarwavelet-based NOMA system(SW-NOMA),a novel multiwavelet modulation based NOMA system(MW-NOMA)scheme has been proposed,and the overall system architecture and process analysis of multiwavelet modulation and demodulation are introduced.The three main points to be considered when using multiwavelet modulation,including the selection of multiwavelet,the analysis of subcarrier function base and the preprocessing of multiwavelet.3.Based on Matlab simulation,the system performance of the MW-NOMA system proposed in this thesis is researched and analyzed,and compared with the SW-NOMA and OFDM-NOMA systems.The simulation results demonstrate that the MW-NOMA system can achieve similar bit error rate to the other two systems,but it has significant advantages in peak-to-average power ratio(PAPR)suppression,and can also achieve greater system capacity than the OFDM-NOMA system.In addition,the only shortcoming of MW-NOMA is that the computational complexity of implementing multiwavelet modulation is slightly larger than that of scalar-wavelet modulation in SWNOMA system,but this is acceptable as a cost.