基于中继选择的星地协作传输系统性能分析

由于星地混合协作网络（hybrid satellite-terrestrial cooperative network，HSTCN）能显著提升卫星通信的服务质量，近年来受到了国内外学者的广泛关注，分析了基于中继选择的星地协作传输系统的性能。首先，在卫星和地面用户之间存在直达链路，并且所有中继节点在采用门限判断译码转发协议辅助卫星通信的情况下，得到用户端经过最大比合并后的输出信噪比（signal-to-noise ratio，SNR）表达式。其次，针对卫星信道服从阴影莱斯分布，而地面信道服从Nakagami-m分布，推导出随机选择和最佳选择两种中继选择策略下系统的中断概率闭合表达式。接着，进一步得到高信噪比条件下中断概率的近似表达式，为分析各种参数对系统性能的影响提供了更加便捷的方法。最后，计算机仿真不仅验证了理论推导的正确性，而且定量分析了协作传输带来的好处，从而为HSTCN技术的实际应用提供理论依据。

Performance analysis of hybrid satellite-terrestrial cooperative transmission system based on relay selection

Hybrid satellite-terrestrial cooperative network (HSTCN) has recently become an attractive research topic due to its potential to improve the quality-of-service of satellite communication. This paper investigates the outage performance of the considered HSTCN based on relay selection. First, by assuming that the maximum ratio combining is utilized at the destination, we obtain the end-to-end signal-to-noise ratio (SNR) by adopting the threshold-based decode-and-forward relay strategy in case that there is a direct link between the satellite and the terrestrial users. Next, the closed-form expressions for outage probability of the considered system with random selection and optimal selection schemes are derived, where the satellite links undergo shadowed-Rician fading, while the terrestrial links follow Nakagami-m fading. Furthermore, the asymptotic outage probability formulas at a high SNR are also developed to reveal the effects of representative parameters on the system performance conveniently. Finally, numerical results confirm the validity of the theoretical formulas and quantitatively analyze the benefits of cooperative transmission, thus providing a theoretical basis for the practical application of the HSTCN technology.