On Routing for Extending Satellite Service Life in LEO Satellite Networks

International audienceWe address the problem of routing for extending the service life of satellites in Iridium-like LEO constellations. Satellites in LEO constellations can spend over 30% of their time under the earth’s umbra, time during which they are powered by batteries. While the batteries are recharged by solar energy, the depth of discharge they reach during eclipse significantly affects their lifetime – and by extension, the service life of the satellites themselves. For batteries of the type that power Iridium satellites, a 15% increase to the depth of discharge can practically cut their service lives in half. We present two new routing metrics – LASER and SLIM – that try to strike a balance between performance and battery depth of discharge in LEO satellite constellations. Our basic approach is to leverage the deterministic movement of satellites for favoring routing traffic over satellites exposed to the sun as opposed to the eclipsed satellites, thereby decreasing the average battery depth of discharge – all without adversely affecting network performance Simulations show that LASER and SLIM can reduce the depth of discharge by about 11% and 16%, respectively, which can lead to as much as 100% increase in the satellite batteries lifetime. This is accomplished by trading off very little in terms of end-to-end delay

Energy efficiency in LEO satellite and terrestrial wired environments

To meet an ever-growing demand for advanced multimedia services and to support electronic connectivity anywhere on the planet, development of ubiquitous broadband multimedia systems is gaining a huge interest at both academic and industry levels. Satellite networks in general and LEO satellite constellations in particular will play an essential role in the deployment of such systems. Therefore, as LEO satellite constellations like Iridium or IridiumNEXT are extremely expensive to deploy and maintain, extending their service lifetimes is of crucial importance. In the main part of this thesis, we propose different techniques for extending satellite service life in LEO satellite constellations. Satellites in such constellations can spend over 30% of their time under the earth’s umbra, time during which they are powered by batteries. While the batteries are recharged by solar energy, the Depth of Discharge (DoD) they reach during eclipse significantly affects their lifetime – and by extension, the service life of the satellites themselves. For batteries of the type that power Iridium and Iridium-NEXT satellites, a 15% increase to the DoD can practically cut their service lives in half. We first focus on routing and propose two new routing metrics – LASER and SLIM – that try to strike a balance between performance and battery DoD in LEO satellite constellations. Our basic approach is to leverage the deterministic movement of satellites for favoring routing traffic over satellites exposed to the sun as opposed to the eclipsed satellites, thereby decreasing the average battery DoD– all without taking a significant penalty in performance. Then, we deal with resource consolidation – a new paradigm for the reduction of the power consumption. It consists in having a carefully selected subset of network links entering a sleep state, and use the rest to transport the required amount of traffic. This possible without causing major disruptions to network activities. Since communication networks are designed over the peak traffic periods, and with redundancy and over-provisioned in mind. As a remedy to these issues, we propose two different methods to perform resource consolidation in LEO networks. First, we propose trafficaware metric for quantifiying the quality of a frugal topology, the Maximum Link Utilization (MLU). With the problem being NP-hard subject to a given MLU threshold, we introduce two heuristics, BASIC and SNAP, which represent different tradeoffs in terms of performance and simplicity. Second, we propose a new lightweight traffic-agnostic metric for quantifiying the quality of a frugal topology, the Adequacy Index (ADI). After showing that the problem of minimizing the power consumption of a LEO network subject to a given ADI threshold is NP-hard, we propose a heuristc named AvOId to solve it. We evaluate both forms of resource consolidation using realistic LEO topologies and traffic requests. The results show that the simple schemes we develop are almost double the satellite batteries lifetime. Following the green networking in LEO systems, the second part of this thesis focuses on extending the resource consolidation schemes to current wired networks. Indeed, the energy consumption of wired networks has been traditionally overlooked. Several studies exhibit that the traffic load of the routers only has a small influence on their energy consumption. Hence, the power consumption in networks is strongly related to the number of active network elements. In this context, we extend the traffic-agnostic metric, ADI, to the wired networks. We model the problem subject to ADI threshold as NP-hard. Then, we propose two polynomial time heuristics – ABStAIn and CuTBAck. Although ABStAIn and CuTBAck are traffic unaware, we assess their behavior under real traffic loads from 3 networks, demonstrating that their performance are comparable to the more complex traffic-aware solutions proposed in the literature

Survey of Inter-satellite Communication for Small Satellite Systems: Physical Layer to Network Layer View

Small satellite systems enable whole new class of missions for navigation, communications, remote sensing and scientific research for both civilian and military purposes. As individual spacecraft are limited by the size, mass and power constraints, mass-produced small satellites in large constellations or clusters could be useful in many science missions such as gravity mapping, tracking of forest fires, finding water resources, etc. Constellation of satellites provide improved spatial and temporal resolution of the target. Small satellite constellations contribute innovative applications by replacing a single asset with several very capable spacecraft which opens the door to new applications. With increasing levels of autonomy, there will be a need for remote communication networks to enable communication between spacecraft. These space based networks will need to configure and maintain dynamic routes, manage intermediate nodes, and reconfigure themselves to achieve mission objectives. Hence, inter-satellite communication is a key aspect when satellites fly in formation. In this paper, we present the various researches being conducted in the small satellite community for implementing inter-satellite communications based on the Open System Interconnection (OSI) model. This paper also reviews the various design parameters applicable to the first three layers of the OSI model, i.e., physical, data link and network layer. Based on the survey, we also present a comprehensive list of design parameters useful for achieving inter-satellite communications for multiple small satellite missions. Specific topics include proposed solutions for some of the challenges faced by small satellite systems, enabling operations using a network of small satellites, and some examples of small satellite missions involving formation flying aspects.Comment: 51 pages, 21 Figures, 11 Tables, accepted in IEEE Communications Surveys and Tutorial

Hybrid Satellite-Terrestrial Communication Networks for the Maritime Internet of Things: Key Technologies, Opportunities, and Challenges

With the rapid development of marine activities, there has been an increasing number of maritime mobile terminals, as well as a growing demand for high-speed and ultra-reliable maritime communications to keep them connected. Traditionally, the maritime Internet of Things (IoT) is enabled by maritime satellites. However, satellites are seriously restricted by their high latency and relatively low data rate. As an alternative, shore & island-based base stations (BSs) can be built to extend the coverage of terrestrial networks using fourth-generation (4G), fifth-generation (5G), and beyond 5G services. Unmanned aerial vehicles can also be exploited to serve as aerial maritime BSs. Despite of all these approaches, there are still open issues for an efficient maritime communication network (MCN). For example, due to the complicated electromagnetic propagation environment, the limited geometrically available BS sites, and rigorous service demands from mission-critical applications, conventional communication and networking theories and methods should be tailored for maritime scenarios. Towards this end, we provide a survey on the demand for maritime communications, the state-of-the-art MCNs, and key technologies for enhancing transmission efficiency, extending network coverage, and provisioning maritime-specific services. Future challenges in developing an environment-aware, service-driven, and integrated satellite-air-ground MCN to be smart enough to utilize external auxiliary information, e.g., sea state and atmosphere conditions, are also discussed

Reducing power consumption in LEO satellite network

Current low earth orbit (LEO) satellite network display poor power efficiency, running network devices at full capacity all the time regardless of the traffic matrix and the distribution of the population over the Globe. Most of the research on energy efficiency of LEO satellites has focused on component level or link level. Therefore, this kind of research is not holistic to try to look at the satellite system as a single node. To enhance the energy efficiency. The solution should exploits multipath routing and load balancing. LEO network is overprovisioned, and hence selectively shutting down some satellite nodes and links during off-peaks hours seems like a good way to reduce energy consumption. In this paper, we exploit the fact that due to geographical and climatic conditions, some satellite links are expected to be loaded with data while others remain unused. Our approach is to power down satellite nodes and links during period of low traffic, while guaranteeing the connectivity and QoS. Finding the optimal solution is NP-problem and therefore, we explore in this work two heuristic algorithms. We evaluate our heuristics on a realistic LEO topology and real traffic matrices. Simulation results show that the power saving can be significant

End-to-end communications in low-rate wireless networks: Problems and solutions in satellite scenarios

Satellite communication links are susceptible to present numerous discontinuities in the transmission. Specific solutions are necessary to be developed to cope this problem. In this sense Delay and Disruptive Tolerant Networks are envisaged as solutions trying to optimize in some sense the communication link. In this TFG the problem of disruptive networks will be studied and possible solutions will be analyzed having in mind satellites scenarios. The work will require the definition of a scenario and the implementation of some state-of-the art solutions in a simulator.Since the Sputnik 1 was first launched in 1957, satellites have taken over the world with their multiple applications in our day-to-day life, specially in the telecommunications field, from television broadcast to mobile communications. One of the main issues they present, is that a single satellite can't provide an end-to-end communication between two spots widely separated. This issue implies that a continuous network between these two spots can never be implemented, and that's why so many public and private companies have been working for a long time in clusters of satellites to provide global coverage of the earth. In the last decade, the M2M (machine-to-machine) communications have become one of the most advanced fields in the engineering world, as they are changing it in order to create a more sophisticated and automatized future. These type of low-rate wireless communications can be supported in a satellite network but they sometimes require a low latency in its channel. In this project, several satellite network scenarios are simulated in order to study the different delays in them and to find the way to optimize the latency in the M2M communication between two fixed spots in the globe, while creating a continuous network made out of GEO and LEO satellites. The project is focused on the idea of finding the best satellite architecture to obtain a fluid communication without any relevant delay along the way, as well as discussing the trade-off between the delay of the signal and the energy consumption of the satellite, specially in the nanosatellite case.Desde que el Sputnik 1 fue lanzado por primera vez en 1957, los satélites han tomado el mundo con sus múltiples aplicaciones en nuestro, especialmente en el campo de las telecomunicaciones, desde la emisión de televisión a las comunicaciones móviles. Uno de los principales problemas que presentan, es que un solo satélite no puede proporcionar una comunicación de extremo a extremo entre dos puntos muy distantes entre sí. Este problema implica que una red contínua entre estos dos puntos no se puede implementar, y es por eso por lo que muchas empresas públicas y privadas han estado trabajando durante mucho tiempo en grupos de satélites para proporcionar una cobertura global de la Tierra. En la última década, las comunicaciones M2M (machine-to-machine) se han convertido en uno de los campos más avanzados en el mundo de la ingeniería, y lo están cambiando con el fin de crear un futuro más sofisticado y automatizado. Este tipo de comunicaciones sin hilos de bajo ritmo de bit puede ser apoyado en una red de satélites, pero que a veces requiere una latencia baja en su canal. En este proyecto, varios escenarios de redes de satélite son simulados con el fin de estudiar los diferentes retardos en todos ellos y en encontrar la manera de optimizar la latencia en la comunicación M2M entre dos puntos fijos en el mundo, usando la creación de una red continua hecha de satélites GEO y LEO. El proyecto se centra en la idea de encontrar la mejor arquitectura de satélites para obtener una comunicación fluida y sin ningún retraso relevante en el camino, así como en discutir el equilibrio entre el retardo de la señal y el consumo de energía del satélite, especialmente en el caso de nanosatélites.Des de que l'Sputnik 1 es llançava per primer cop el 1957, els satèl·lits han dominat el món amb les seves múltiples aplicacions en la nostra vida quotidiana, especialment en el camp de les telecomunicacions, des de difusió de televisió a les comunicacions mòbils. Una de les principals qüestions que presenten, és que un únic satèl·lit no pot proporcionar una comunicació extrem a extrem entre dos punts molt distants. Això implica que mai no es pugui implementar una xarxa contínua entre aquests dos punts, i és per això que moltes empreses públiques i privades han estat treballant durant molt temps en agrupacions de satèl·lits per donar cobertura global de la terra. En la darrera dècada, les comunicacions de M2M (machine-to-machine) han esdevingut un dels camps més avançats del món de l'enginyeria, ja que estan canviant-lo per tal de crear un més sofisticat i automatitzat futur. Aquests tipus de comunicacions sense fils de baix ritme de bit poden ser recolzades en una xarxa de satèl·lits però de vegades requereixen una latència baixa al seu canal. En aquest projecte, diversos escenaris de xarxes de satèl·lits són simulats per tal d'estudiar els diferents retards en tots ells i en trobar la manera d'optimitzar la latència en la comunicació M2M entre dos punts fixos en el món, utilitzant la creació d'una xarxa contínua de satèl·lits GEO i LEO. El projecte es centra en la idea de trobar la millor arquitectura de satèl·lits per obtenir una comunicació fluida sense demora pertinent en el camí, així com en discutir la solució de compromís que existeix entre el retard del senyal i el consum energètic del satèl·lit, especialment en el cas dels nanosatèl·lits

Design and Implementation of a Narrow-Band Intersatellite Network with Limited Onboard Resources for IoT

Satellite networks are inevitable for the ubiquitous connectivity of M2M (machine to machine) and IoT (internet of things) devices. Advances in the miniaturization of satellite technology make networks in LEO (Low Earth Orbit) predestined to serve as a backhaul for narrow-band M2M communication. To reduce latency and increase network responsivity, intersatellite link capability among nodes is a key component in satellite design. The miniaturization of nodes to enable the economical deployment of large networks is also crucial. Thus, this article addresses these key issues and presents a design methodology and implementation of an adaptive network architecture considering highly limited resources, as is the case in a nanosatellite (≈10 kg) network. Potentially applicable multiple access techniques are evaluated. The results show that a time division duplex scheme with session-oriented P2P (point to point) protocols in the data link layer is more suitable for limited resources. Furthermore, an applicable layer model is defined and a protocol implementation is outlined. To demonstrate the technical feasibility of a nanosatellite-based communication network, the S-NET (S band network with nanosatellites) mission has been developed, which consists of four nanosatellites, to demonstrate multi-point crosslink with 100 kbps data rates over distances up to 400 km and optimized communication protocols, pushing the technological boundaries of nanosatellites. The flight results of S-NET prove the feasibility of these nanosatellites as a space-based M2M backhaul.BMWi, 50YB1225, S-Band Netzwerk für kooperierende SatellitenBMWi, 50YB1009, SLink - S-Band Transceiver zur Intersatelliten-Kommunikation von NanosatellitenDFG, 414044773, Open Access Publizieren 2019 - 2020 / Technische Universität Berli

Reinforcement learning for resource allocation in LEO satellite networks

Published versio

Internet of Satellites (IoSat): analysis of network models and routing protocol requirements

The space segment has been evolved from monolithic to distributed satellite systems. One of these distributed systems is called the federated satellite system (FSS) which aims at establishing a win-win collaboration between satellites to improve their mission performance by using the unused on-board resources. The FSS concept requires sporadic and direct communications between satellites, using inter satellite links. However, this point-to-point communication is temporal and thus it can break existent federations. Therefore, the conception of a multi-hop scenario needs to be addressed. This is the goal of the Internet of satellites (IoSat) paradigm which, as opposed to a common backbone, proposes the creation of a network using a peer-to-peer architecture. In particular, the same satellites take part of the network by establishing intermediate collaborations to deploy a FSS. This paradigm supposes a major challenge in terms of network definition and routing protocol. Therefore, this paper not only details the IoSat paradigm, but it also analyses the different satellite network models. Furthermore, it evaluates the routing protocol candidates that could be used to implement the IoSat paradigm.Peer ReviewedPostprint (author's final draft

Energy-efficient satellite joint computation and communication

The emerging interest in satellite networks will be a key driver in the path to 6G. The satellite segment must be conceived beyond a mere relay system, where nodes can process data and offload the terrestrial segment. Besides, evidence suggests that energy consumption is among the most important factors for the design of future communication networks. For this motivation, we introduce Sat2C, an energy-efficient algorithm for satellite joint routing, radio resource allocation and task offloading for latency-constrained services. We develop a novel energy model that incorporates the power amplifier subsystem and changes the geometry of the problem. Regarding the routing task, we propose the SHIELD algorithm, based on the submodularity framework and which achieves Pareto-efficient routes. Besides, the RRM problem is formulated as a log-log convex program. The experimental results reveal that Sat2C has low computational complexity, provides routes with low variance in the mean distance and the transmission powers are optimal to ensure energy minimization