Logical topology-based routing in LEO constellations

Satellite communication is distinguished by global coverage and the ability to support a wide range of applications. LEO (Low Earth Orbit) satellite systems employing inter-satellite links offer rich connectivity in space and provide direct broadband access and personal communication service. One of the technical challenges for LEO systems is the design of efficient routing strategies tailored to their highly dynamic nature. In this paper, we present a new routing method which solves the routing problem effciently by overlaying a static logical topology over the physical constellation. The algorithm generates near-optimal shortest paths. The performance of our proposed scheme is evaluated through theoretical analysis and simulations.published_or_final_versio

Supporting IP/LEO satellite networks by handover-independent IP mobility management

科研費報告書収録論文(課題番号:14380172・基盤研究(B)(2) ・H14～H15/研究代表者:根元, 義章/トラヒックパターンの時系列解析に基づく次世代広域不正アクセス自動追跡システム

Explicit Load Balancing Technique for NGEO Satellite IP Networks With On-Board Processing Capabilities

科研費報告書収録論文(課題番号:17500030/研究代表者:加藤寧/インターネットと高親和性を有する次世代低軌道衛星ネットワークに関する基盤研究

Optimization of Reconfigurable Satellite Constellations Using Simulated Annealing and Genetic Algorithm

Agile Earth observation can be achieved with responsiveness in satellite launches, sensor pointing, or orbit reconfiguration. This study presents a framework for designing reconfigurable satellite constellations capable of both regular Earth observation and disaster monitoring. These observation modes are termed global observation mode and regional observation mode, constituting a reconfigurable satellite constellation (ReCon). Systems engineering approaches are employed to formulate this multidisciplinary problem of co-optimizing satellite design and orbits. Two heuristic methods, simulated annealing (SA) and genetic algorithm (GA), are widely used for discrete combinatorial problems and therefore used in this study to benchmark against a gradient-based method. Point-based SA performed similar or slightly better than the gradient-based method, whereas population-based GA outperformed the other two. The resultant ReCon satellite design is physically feasible and offers performance-to-cost(mass) superior to static constellations. Ongoing research on observation scheduling and constellation management will extend the ReCon applications to radar imaging and radio occultation beyond visible wavelengths and nearby spectrums. Keywords: Earth observation; remote sensing; satellite constellation; reconfigurability; repeat ground tracks; simulated annealing; genetic algorith

Analysis of OSPFv3 in LEO satellite networks

Communication via satellite networks is under continuous research and development as it offers many advances over traditional terrestrial networks such as global coverage, but has a major drawback to be solved, the problem of point-to-point routing. In this work we have developed a satellite network emulator using Linux containers, which has allowed us to analyze the behavior of the IP routing protocol OSPFv3 in this type of networks. Specifically, its behavior has been analyzed in the Iridium constellation, which is widely known and used in this type of studies. For this purpose, we have used files of the topology of these networks over time generated with the HypatiaSeam orbital propagator, a modification of Hypatia made by the SeamSAT research group of the UPC. This project is part of a more global project whose objective is to be able to use a network of LEO satellites for communication between aircraft and airspace control centers. This would make it possible to centralize the different control centers, since it would not be necessary for aircraft to be in direct range to communicate with these centers, but thanks to the global coverage provided by these networks, they could communicate from anywhere in the world. Specifically, in this project we have developed an emulation platform that has allowed us to analyze the behavior of the OSPFv3 protocol to find optimal routes, i.e., shortest distance in terms of the cost function of the protocol. We will present the design and implementation of the emulation platform as well as the analysis of OSPFv3 performance in terms of protocol convergence time to topology changes, number of hops between a satellite and a ground station, delay and loss rate

Revolutionizing Future Connectivity: A Contemporary Survey on AI-empowered Satellite-based Non-Terrestrial Networks in 6G

Non-Terrestrial Networks (NTN) are expected to be a critical component of 6th Generation (6G) networks, providing ubiquitous, continuous, and scalable services. Satellites emerge as the primary enabler for NTN, leveraging their extensive coverage, stable orbits, scalability, and adherence to international regulations. However, satellite-based NTN presents unique challenges, including long propagation delay, high Doppler shift, frequent handovers, spectrum sharing complexities, and intricate beam and resource allocation, among others. The integration of NTNs into existing terrestrial networks in 6G introduces a range of novel challenges, including task offloading, network routing, network slicing, and many more. To tackle all these obstacles, this paper proposes Artificial Intelligence (AI) as a promising solution, harnessing its ability to capture intricate correlations among diverse network parameters. We begin by providing a comprehensive background on NTN and AI, highlighting the potential of AI techniques in addressing various NTN challenges. Next, we present an overview of existing works, emphasizing AI as an enabling tool for satellite-based NTN, and explore potential research directions. Furthermore, we discuss ongoing research efforts that aim to enable AI in satellite-based NTN through software-defined implementations, while also discussing the associated challenges. Finally, we conclude by providing insights and recommendations for enabling AI-driven satellite-based NTN in future 6G networks.Comment: 40 pages, 19 Figure, 10 Tables, Surve

Performance Analysis of Protocol Independent Multicasting-Dense Mode in Low Earth Orbit Satellite Networks

This research explored the implementation of Protocol Independent Multicasting - Dense Mode (PIM-DM) in a LEO satellite constellation. PIM-DM is a terrestrial protocol for distributing traffic efficiently between subscriber nodes by combining data streams into a tree-based structure, spreading from the root of the tree to the branches. Using this structure, a minimum number of connections are required to transfer data, decreasing the load on intermediate satellite routers. The PIM-DM protocol was developed for terrestrial systems and this research implemented an adaptation of this protocol in a satellite system. This research examined the PIM-DM performance characteristics which were compared to earlier work for On- Demand Multicast Routing Protocol (ODMRP) and Distance Vector Multicasting Routing Protocol (DVMRP) - all in a LEO satellite network environment. Experimental results show that PIM-DM is extremely scalable and has equivalent performance across diverse workloads. Three performance metrics are used to determine protocol performance in the dynamic LEO satellite environment, including Data-to- Overhead ratio, Received-to-Sent ratio, and End-to-End Delay. The OPNET® simulations show that the PIM-DM Data-to-Overhead ratio is approximately 80% and the protocol reliability is extremely high, achieving a Receive-to-Sent ratio of 99.98% across all loading levels. Finally, the PIM-DM protocol introduces minimal delay, exhibiting an average End-to-End Delay of approximately 76 ms; this is well within the time necessary to support real-time communications. Though fundamental differences between the DVMRP, ODMRP, and PIM-DM implementations precluded a direct comparison for each experiment, by comparing average values, PIM-DM generally provides equivalent or better performance