In this paper, we propose an approach for constructing a multi-layer multi-orbit space information network (SIN) to provide high-speed continuous broadband connectivity for space missions (nanosatellite terminals) from the emerging space-based Internet providers. This notion has been motivated by the rapid developments in satellite technologies in terms of satellite miniaturization and reusable rocket launch, as well as the increased number of nanosatellite constellations in lower orbits for space downstream applications, such as earth observation, remote sensing, and Internet of Things (IoT) data collection. Specifically, space-based Internet providers, such as Starlink, OneWeb, and SES O3b, can be utilized for broadband connectivity directly to/from the nanosatellites, which allows a larger degree of connectivity in space network topologies. Besides, this kind of establishment is more economically efficient and eliminates the need for an excessive number of ground stations while achieving real-time and reliable space communications. This objective necessitates developing suitable radio access schemes and efficient scalable space backhauling using inter-satellite links (ISLs) and inter-orbit links (IOLs). Particularly, service-oriented radio access methods in addition to software-defined networking (SDN)-based architecture employing optimal routing mechanisms over multiple ISLs and IOLs are the most essential enablers for this novel concept. Thus, developing this symbiotic interaction between versatile satellite nodes across different orbits will lead to a breakthrough in the way that future downstream space missions and satellite networks are designed and operated.
NOMA versus OMA in Finite Blocklength Regime: Link-Layer Rate Performance
在本文中，我们研究了非正交多址接入（NOMA）和正交多址接入（OMA）技术在有限块长度制度的延迟性能。在比较研究中，我们得出了两个用户NOMA和OMA对应的延迟服务质量的约束下，可实现的有效容量。然后，我们得到封闭形式的表达式，可实现的有效容量的弱和强的用户在这两种情况下，考虑在瑞利衰落信道传输。数值结果提供。特别是，它示出，在低信号噪声比（SNR），具有更好的信道条件的OMA用户优于两个NOMA用户。\blue{We also evaluate the impact of fixed power allocation scheme on the achievable effective capacity of two-user NOMA.}对链路层总速率的比较分析表明，在高信噪比时，有限块长NOMA的链路层总速率优于时延指数较松的OMA。
