The satellite-terrestrial networks (STN) utilize the spacious coverage and low transmission latency of the Low Earth Orbit (LEO) constellation to transfer requested content for subscribers especially in remote areas. With the development of storage and computing capacity of satellite onboard equipment, it is considered promising to leverage in-network caching technology on STN to improve content distribution efficiency. However, traditional caching and distribution schemes are not suitable in STN, considering dynamic satellite propagation links and time-varying topology. More specifically, the unevenness of user distribution heightens difficulties for assurance of user quality of experience. To address these problems, we first propose a density-based network division algorithm. The STN is divided into a series of blocks with different sizes to amortize the data delivery costs. To deploy the caching satellites, we analyze the link connectivity and propose an approximate minimum coverage vertex set algorithm. Then, a novel cache node selection algorithm is designed for optimal subscriber matching. On the basis of time-varying network model, the STN cache content updating mechanism is derived to enable a stable and sustainable quality of user experience. The simulation results demonstrate that the proposed user-oriented STN content distribution scheme can obviously reduce the average propagation delay and network load under different network conditions and has better stability and self-adaptability under continuous time variation. 

QoE-Aware Efficient Content Distribution Scheme For Satellite-Terrestrial Networks

The LEO satellite network is an important part of the communication network, among which the inter-satellite link (ISL) undertakes the main data transmission task. The routing technology in LEO constellation is an important technical component of the satellite communication system. However, the design of ISL routing algorithm is not easy. It is necessary to consider the relative motion between satellites, the data transmission capacity of nodes and the reliability of links. Moreover, the algorithm should be adaptive to face all kinds of emergencies. Based on the above considerations, this paper proposes a multi-constraint optimal routing algorithm (MCORA) in LEO satellite networks. By analyzing various parameters that may affect data transmission, the link selection problem is transformed into a multi-constraint optimal problem. In order to avoid getting trapped in local optimal solution during path finding, an improved ant colony algorithm is proposed. So MCORA not only considers the optimal link selection but also considers the reliability and load balancing of the whole network. Simulation results show that the MCORA scheme obtains better link performance, indicating the proposed routing algorithm is feasible.

A multi-constraint optimal routing algorithm in LEO satellite networks

The ever-increasing demand for ubiquitous and differentiated services at anytime and anywhere emphasizes the necessity of aerospace integrated networks (AINs) which consist of multi-tiers, e.g., high-altitude platforms (HAPs) tier, unmanned aerial vehicles (UAVs) tier, low earth orbit (LEO) satellites tier, etc. for wide coverage and high capacity. However, the inherent heterogeneity, time-variability, and differentiated mobility characteristics between terrestrial networks and AINs constraint the materialization of the aforementioned widely expected potentials of AINs. Therefore, it is crucial to make a profound understanding of AINs’ impacts on pivotal models and methodologies for enabling 6G, thus providing technology reference for AINs empowering 6G. To understand the latest development and ultimately open new research niches on this significant topic, this survey is the pioneer paper to serve as a systematical and comprehensive overview in both single-tier scenarios and combining-tiers scenarios in AINs. We start with a profound discussion about the state-of-the-art potentially promising methodologies and models in the era of AINs empowering 6G from the perspective of the system architecture and networking design and enabling technologies of AINs, to enable flexible and scalable management and control of the AINs and ensure network stability. Furthermore, we make an in-depth literature overview across the network dynamics modeling, theoretical performance analysis model, and system optimization to enhance the system performance and guarantee user-on-demand services. Additionally, we highlight the ongoing research challenges and future directions with focusing on the development trend of ultra-dense satellite constellations in 6G.

Aerospace Integrated Networks Innovation for Empowering 6G: A Survey and Future Challenges

Method of Rain Attenuation Prediction Based on Long–Short Term Memory Network

When using link-state protocols such as OSPF or IS-IS, forwarding loops can occur transiently when the routers adapt their forwarding tables as a response to a topological change. In this paper, we present a mechanism that lets the network converge to its optimal forwarding state without risking any transient loops and the related packet loss. The mechanism is based on an ordering of the updates of the forwarding tables of the routers. Our solution can be used in the case of a planned change in the state of a set of links and in the case of unpredictable changes when combined with a local protection scheme. The supported topology changes are link transitions from up to down, down to up, and updates of link metrics. Finally, we show by simulations that sub-second loop-free convergence is possible on a large Tier-1 ISP network.

Avoiding transient loops during the convergence of link-state routing protocols

Low earth orbit (LEO) satellite systems, an important part of the next generation of global communication systems, have the advantages of low transmission delay, low satellite cost and low launch cost. The construction of an LEO satellite network with global coverage has become the direction of future space network transmission development. Although extensive research has been conducted on the routing of LEO satellite networks, most papers focus on only space segment routing, with little attention paid to the route between the satellite and ground station. This paper introduces the transmission scenario of ground station switching with connected satellites and analyzes the problem of data packet loss caused by ground station and satellite communication link switching. Two optimization strategies based on static routing and dynamic routing are proposed as solutions to the problem of data packet loss, with software-simulated test results showing that both approaches can effectively avoid packet loss.

/pdf/optimization-strategy-to-solve-transmission-interruption-ds14q43ngu.pdf

Hefeng Bai

Papers

Optimization Strategy to Solve Transmission Interruption Caused by Satellite-Ground Link Switching