System-Level Simulation Of Non-Orthogonal Multiple Access Technologies In 5G Mobile Communication Network

As the key technology of mobile communication systems,multiple access scheme decides the system performance and capacity directly.Based on the orthogonal multiple access(OMA),the previous four generations of mobile communication systems accommodate multiples users without inter-user interference,as a result of which,system complexity is decreased effectively.However,with the rapid growth of users and high-rate services,these orthogonal multiple access technologies can not satisfy the requirement of future mobile communications due to the restricted frequency efficiency and access capability.Consequently,non-orthogonal multiple access technologies are paid extensive attention in the research of fifth generation(5G)mobile communication system.As two most important multiple access candidate schemes in 5G,SCMA(Sparse Code Multiple Access)and NOMA(Non-orthogonal Multiple Access)are simulated in the thesis,based on which,the impacts on system performance exerted by interference,power allocation and so on are analyzed.Based on the basic analysis of system model and key techniques of SCMA system,the system-level simulation platform is described,involving the basic parameters and flow chart,with the emphasis on the simulation implementation of SCMA non-orthogonal multiple access on the platform.Further,based on the platform,the OFDMA(Orthogonal Frequency Division Multiplexing Access)and SCMA system are simulated and compared,which shows that SCMA performs better than OFDMA in terms of number of accessible users as well as system throughput.Further,the thesis analyzes how the adaptive modulation and coding improve the system performance and how the intra-cell interference impacts the desired signal.Based on the introduction to the NOMA system model,the user fairness in NOMA system is studied in the thesis.By using Lagrangian multiplier method,cell fairness index(CFI)and utility function a,the thesis simulates power allocation optimization algorithm with the fairness constraint to obtain the performance curves under the conditions of different cell users,various cell radius and diverse transmission power,which can provide some guidance to the design of NOMA system.