Satellite communications have become a hot topic due to their ability to serve users with wide coverage and instant access.This paper investigates the performance of a satellite system with semi-grant-free(SGF)transmission scheme.To improve spectrum efficiency and access ability,we propose a non-orthogonal multiple access-based SGF transmission scheme,considering the feature of satellite communications by using the available statistical channel state information.We assume that the satellite links obey shadowed-Rician distribution,thus given the two cases,random access or distribution contention for mobile terminals,the closed-form outage probabilities of the earth station and mobile terminals,as well as the system throughput expression are derived.Simulation results demonstrate the effectiveness of the theoretical analysis and the superiority of the proposed schemes.Simulations also quantitatively analyze the influences of typical parameters,such as the user number,and the target data rate,on the system's performance.
关键词
卫星通信/统计信道状态信息/非正交多址接入/半免授权传输/阴影莱斯衰落
Key words
satellite communications/statistical channel state information/non-orthogonal multiple access/semi-grant-free transmission/shadowed-Rician fading
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