On Layer And Power Allocation Study For SCMA Systems

With the continuous development of communication technology and the increasing de-mand of users, the research on fifth generation (5G) mobile communication system has been highly concerned by academic circles. According to the key performance indicators and sys-tem design requirements of the 5G system, 5G networks are supposed to support higher throughput, lower delay, better quality of service (QoS) and mass links and so on. Because the number of access users is directly proportional to orthogonal resources, orthogonal mul-tiple access technology for 4G can not meet the needs of 5G large capacity, massive connec-tion, low latency access requirements. Therefore, non orthogonal multiple access has become the focus of the current 5G multiple access technology.This thesis mainly focuses on the current main research of the non orthogonal technol-ogy proposed by HUAWEI, Sparse Code Multiple Access (SCMA) technology, including its research and analysis of the main key technology of SCMA. It is mainly aimed at the SCMA transmission system for overload, and an SCMA layer and the power allocation scheme based on capacity and energy efficiency respectively. In addition the performance of the si-mulation is analyzed. The main research contents and contributions are as follows:First, the basic principle of SCMA technology is introduced. Then a detailed analysis of the SCMA uplink and downlink design, SCMA receiver detection scheme and the advantag-es of SCMA technology are proposed, which lays a foundation for the subsequent perfor-mance analysis and design.Second, simulation and analysis of the relationship between the SCMA overloaing factor and codebook, the impact of overload factor on the system BER performance are presented respectively. We compare the codebook sparsity performance of SCMA and LDS(Low Density Signature), which shows that SCMA outperforms LDS in term of system BER. And then, the relationship between the overload factor and the system capacity is analyzed. The influence of the number of users, the number of codebooks and the layer power on the system capacity is also analyzed.Third, in the SCMA transmission system, the SCMA layer and the power allocation scheme are proposed to maximize the system capacity and system energy efficiency respec-tively. By using Lagrange duality theory, we solve the SCMA layer distribution vector and its optimal power. Finally, simulation results verify the effectiveness of the proposed schemes, and show that the system capacity of joint layer and power allocation algorithm based on maximizing system capacity is improved significantly compared to average power algorithm, and the energy efficiency of joint layer and power allocation algorithm based on maximizing system energy efficiency is improved significantly compared to average power algorithm.