Research On Application Of Multiwavelet In 5G Communication Waveform Design

Non-orthogonal multiple access(NOMA)is one of the key technologies in the research on 5G communication.However,the bit error rate performance is degraded and sensitive to the power allocation ratio due to the introduction of inter-user interference in NOMA system.Therefore,a new waveform design method is urgently needed to further enhance the reliability and feasibility of NOMA system.Multiwavelets have superiorities of possessing many promising properties such as symmetry,orthogonality and short support simultaneously.Hence,the waveform design based on multiwavelets can be exploited as a new approach for the waveform design of NOMA communication system.Based on multiwavelets theory and implementation method,this paper studies the system performance which combines multiwavelets and NOMA by considering the characteristics of NOMA technology,with the purpose to provide technical support for waveform design of next-generation mobile communication systems.The main work done in this paper is as follows:1.From the perspective of multi-carrier modulation,this paper investigates the waveform design method suitable for NOMA communication system based on multi-wavelet transformation.Multiwavelets and multi-carrier modulation principles are firstly studied in this article.Then replace the fourier transform in traditional OFDM modulation with preprocessing and multiwavelets transform to perform multi-carrier modulation in NOMA system.2.This thesis also analyzes the main features of the NOMA transmission system,the way to superimpose users' signals and the main properties of multiwavelets functions,and based on which an innovative pulse-shaping waveform design scheme tailored for NOMA system is proposed,where it utilizes different pulse-shping filters extracted from a same multiwavelet to pulseshape different paired users in NOMA.3.The MATLAB simulation analyses of the NOMA system architecture under the two waveform schemes are conducted,compared with the performance of the existing NOMA system under the traditional waveform design method.Results demonstrate that the one focused on the multiwavelets multi-carrier modulation can achieve a lower PAPR under the condition that the layer of wavelet decomposition is relatively low.The other one proposed in this paper,focused on the multi-wavelet pulse-shaping waveform design,is verified to have realized better BER performance for NOMA system and been less affected by the power allocation than the tranditional pulse shaping when the bandwidth restriction is not too strict.Simultaneously,some key factors affecting the proposed waveform design schemes are analyzed and discussed.In addition,by adjusting the cutoff frequency of the LPF in the proposed multiwavelets pulse-shaping NOMA system,the tradeoff between user transmission reliability and bandwidth becames egotiable.