Congestion management techniques for disruption-tolerant satellite networks

Delay and disruption-tolerant networks are becoming an appealing solution for extending Internet boundaries toward challenged environments where end-to-end connectivity cannot be guaranteed. In particular, satellite networks can take advantage of a priori trajectory estimations of nodes to make efficient routing decisions. Despite this knowledge is already used in routing schemes such as contact graph routing, it might derive in congestion problems because of capacity overbooking of forthcoming connections (contacts). In this work, we initially extend contact graph routing to provide enhanced congestion mitigation capabilities by taking advantage of the local traffic information available at each node. However, since satellite networks data generation is generally managed by a mission operation center, a global view of the traffic can also be exploited to further improve the latter scheme. As a result, we present a novel strategy to avoid congestion in predictable delay- and disruption-tolerant network systems by means of individual contact plans. Finally, we evaluate and compare the performance improvement of these mechanisms in a typical low Earth orbit satellite constellation.Fil: Madoery, Pablo Gustavo. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Estudios Avanzados en Ingeniería y Tecnología. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Estudios Avanzados en Ingeniería y Tecnología; ArgentinaFil: Fraire, Juan Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Estudios Avanzados en Ingeniería y Tecnología. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Estudios Avanzados en Ingeniería y Tecnología; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; ArgentinaFil: Finochietto, Jorge Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Estudios Avanzados en Ingeniería y Tecnología. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Estudios Avanzados en Ingeniería y Tecnología; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentin

Routing in the Space Internet: A contact graph routing tutorial

A Space Internet is possible, as long as the delay and disruption challenges imposed by the space environment are properly tackled. Because these conditions are not well addressed by terrestrial Internet, more capable Delay-Tolerant Networking (DTN) protocols and algorithms are being developed. In particular, the principles and techniques for routing among ground elements and spacecraft in near-Earth orbit and deep-space are enacted in the Contact Graph Routing (CGR) framework. CGR blends a set of non-trivial algorithm adaptations, space operations concepts, time-dynamic scheduling, and specific graph models. The complexity of that framework suggests a need for a focused discussion to facilitate its direct and correct apprehension. To this end, we present an in-depth tutorial that collects and organizes first-hand experience on researching, developing, implementing, and standardizing CGR. Content is laid out in a structure that considers the planning, route search and management, and forwarding phases bridging ground and space domains. We rely on intuitive graphical examples, supporting code material, and references to flight-grade CGR implementations details where pertinent. We hope this tutorial will serve as a valuable resource for engineers and that researchers can also apply the insights presented here to topics in DTN research.Fil: Fraire, Juan Andres. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina. Universitat Saarland; AlemaniaFil: De Jonckère, Olivier. Technische Universität Dresden; AlemaniaFil: Burleigh, Scott C.. California Institute of Technology; Estados Unido

On route table computation strategies in Delay-Tolerant Satellite Networks

Delay-Tolerant Networking (DTN) has been proposed for satellite networks with no expectation of continuous or instantaneous end-to-end connectivity, which are known as Delay-Tolerant Satellite Networks (DTSNs). Path computation over large and highly-dynamic yet predictable topologies of such networks requires complex algorithms such as Contact Graph Routing (CGR) to calculate route tables, which can become extremely large and limit forwarding performance if all possible routes are considered. In this work, we discuss these issues in the context of CGR and propose alternatives to the existing route computation scheme: first-ending, first-depleted, one-route, and per-neighbor strategies. Simulation results over realistic DTSN constellation scenarios show that network flow metrics and overall calculation effort can be significantly improved by adopting these novel route table computation strategies.Fil: Fraire, Juan Andres. Universidad Nacional de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Estudios Avanzados en Ingeniería y Tecnología. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Estudios Avanzados en Ingeniería y Tecnología; ArgentinaFil: Madoery, Pablo Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Estudios Avanzados en Ingeniería y Tecnología. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Estudios Avanzados en Ingeniería y Tecnología; Argentina. Universidad Nacional de Córdoba; ArgentinaFil: Charif, Amir (EXT). Commissariat A Energie Atomique; FranciaFil: Finochietto, Jorge Manuel. Universidad Nacional de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Estudios Avanzados en Ingeniería y Tecnología. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Estudios Avanzados en Ingeniería y Tecnología; Argentin

Battery-aware contact plan design for LEO satellite constellations: The ulloriaq case study

Power demands of communication technologies between LEO small-satellites are difficult to counterbalance by solar infeed and on-board battery storage, due to size and weight limitations. This makes the problem of battery-powered intersatellite communication a very difficult one. Its management requires a profound understanding as well as techniques for a proper extrapolation of the electric power budget as part of the inter-satellite and satellite-to-ground communication design. We discuss how the construction of contact plans in delay tolerant networking can profit from a sophisticated model of the on-board battery behavior. This model accounts for both nonlinearities in battery behavior as well as stochastic fluctuations in charge, so as to control the risk of battery depletion. We take an hypothetical Ulloriaq constellation based on the GOMX–4 satellites from GomSpace as a reference for our studies.Fil: Fraire, Juan Andres. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina. Universitat Saarland; AlemaniaFil: Nies, Gilles. Universitat Saarland; AlemaniaFil: Gerstacker, Carsten. Universitat Saarland; AlemaniaFil: Hermanns, Holger. Universitat Saarland; Alemania. Institute of Intelligent Software; ChinaFil: Bay, Kristian. GomSpace A/S; DinamarcaFil: Bisgaard, Morten. GomSpace A/S; Dinamarc

Design challenges in contact plans for disruption-tolerant satellite networks

During the past 20 years, space communications technologies have shown limited progress in comparison to Internet-based networks on Earth. However, a brand new working group of the IETF with focus on DTN promises to extend today's Internet boundaries to embrace disruptive communications such as those seen in space networks. Nevertheless, several challenges need to be overcome before operative DTNs can be deployed in orbit. We analyze the state of the art of effective design, planning, and implementation of the forthcoming network communications opportunities (contacts). To this end, different modeling techniques, system constraints, selection criteria, and methods are reviewed and compared. Finally, we discuss the increasing complexity of considering routing and traffic information to enrich the planning procedure, yielding the need to implement a contact plan computation element to support space DTN operation.Fil: Fraire, Juan Andres. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; ArgentinaFil: Finochietto, Jorge Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Estudios Avanzados En Ingeniería y Tecnología. Universidad Nacional de Córdoba. Facultad de Ciencias exactas Físicas y Naturales. Instituto de Estudios Avanzados En Ingeniería y Tecnología; Argentin

Routing-aware fair contact plan design for predictable delay tolerant networks

Delay tolerant networks (DTNs) have become a promising solution for extending Internet boundaries to challenged environments such as satellite constellations. In this context, strategies to exploit scarce communication opportunities, while still considering device and application constraints, are still to be investigated to enable the actual deployment of these networks. In particular, the Contact Graph Routing (CGR) scheme has been proposed as it takes advantage of the contact plan, which comprises all future contacts among nodes. However, resource constraints can forbid the totality of these contacts to belong to the contact plan; thus, only those which together meet an overall goal shall be selected. In this article, we consider the problem of designing a contact plan that can provide fairness in link assignment and minimal all-to-all route delay; therefore, achieving equal contact opportunities while favoring end-to-end traffic latency. We formalize this by means of a multi-objective optimization model that can be computationally intractable for large topologies; thus, heuristic algorithms are proposed to compute the contact plan in practice. Finally, we analyze general results from these routines and discuss how they can used to provision valuable contact plans for real networks.Fil: Fraire, Juan Andres. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba; ArgentinaFil: Finochietto, Jorge Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba; Argentin

Contact plan design for GNSS constellations: A case study with Optical Inter-Satellite Links

Optical Inter-Satellite Links (OISLs) are being con-sidered for future Global Navigation Satellite System (GNSS)constellations. Thanks to OISLs, the constellation incorporatesimproved clock synchronization and precise ranging among thesatellites, which are essential features to achieve accurate timeand orbit determination. High data rate communications withinthe space segment also reduce ground segment dependency, bymeans of decentralized access to information. However, the dualoptimization of data and navigation performance metrics requiresa careful assignment of OISLs to the available laser communica-tion terminals on-board. To this end, we present a Contact PlanDesign (CPD) scheme based on a Degree Constrained MinimumSpanning Tree heuristic applied to such OISL-enabled GNSS (O-GNSS) constellations. Results on the Kepler system, a novel GNSSproposal, show that a fair distribution of connectivity among theconstellation can be ensured while optimizing its range-basedposition estimation capabilities (PDOP). A PDOP improvementof 85 % is reached on average by the optimized contact plan withrespect to a generic scheduler that disregards the geometricaldistribution of the chosen links.Fil: Nardin, Andrea. Politecnico di Torino; ItaliaFil: Fraire, Juan Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Estudios Avanzados en Ingeniería y Tecnología. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Estudios Avanzados en Ingeniería y Tecnología; ArgentinaFil: Dovis, Fabio. Politecnico di Torino; Itali

Empowering the Tracking Performance of LEO-Based Positioning by Means of Meta-Signals

Global Navigation Satellite Systems (GNSSs) are the most widespread technology for Position Navigation and Timing (PNT). They have been traditionally deployed exploiting Medium Earth Orbit (MEO) or Geosynchronous Orbit (GSO) satellites. To meet future demands and overcome MEO and GSO limitations, GNSSs based on Low Earth Orbit (LEO) constellations have been investigated as a radical system change. Although characterized by a higher Doppler effect, a PNT service supplied by LEO satellites can provide received signals that are about 30 dB stronger. Moreover, broadband LEO constellations and the forthcoming mega-constellations can be exploited to deliver a piggybacked PNT service. With this cost-effective solution, a PNT service might be subject to substantial bandwidth limitations. A narrowband implementation of the so-called meta-signal approach in GNSS receivers, namely Virtual Wideband (VWB), can tolerate harsh Doppler conditions while reducing the processed bandwidth. It is thus suited to a secondary PNT service delivered by LEO satellites. The aim of this work is to show the applicability of the VWB architecture to signals provided by a piggybacked PNT service, hosted on a mega-constellation. Through this case study we demonstrate the capability of this implementation to bear high Doppler conditions while empowering the potential of LEO PNT.Fil: Nardin, Andrea. Politecnico di Torino; ItaliaFil: Dovis, Fabio. Politecnico di Torino; ItaliaFil: Fraire, Juan Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Estudios Avanzados en Ingeniería y Tecnología. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Estudios Avanzados en Ingeniería y Tecnología; Argentina. Universite Claude Bernard Lyon 1. Institut de Physique Nucléaire de Lyon.; Franci

OpenCL overview, implementation, and performance comparison

High performance parallel computing was something exclusive for expensive specialized hardware some years ago. But now we can find powerful parallel processors in many home graphics card whose interface has been recently opened by many manufacturers for general purpose computing. OpenCL, created by the world most important processors manufacturers, went a little further, aiming for a platform and manufacturer independent parallel language. However, understanding this new processing paradigm is challenging and critical for future computation demanding applications. The first approach of this document is to provide a deep technical background of OpenCL architecture. Second, we propose an implementation of a matrix product calculation OpenCL kernel directly implemented in C++ without wrappers so as to describe in detail the OpenCL programming flow. Thirdly, different platforms and algebraic scenarios are created for this program concluding that the improvement of calculation performance can reach up to 3 orders of magnitude over the same algorithm in plain C++.Fil: Fraire, Juan Andres. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ferreyra, Pablo Alejandro. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Marques, Carlos Alberto. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Traffic-aware contact plan design for disruption-tolerant space sensor networks

Delay and disruption tolerant networks (DTNs) are becoming an appealing solution for extending Internet boundaries across challenged network environments. In particular, if node mobility can be predicted as in space sensor networks (SSNs), routing schemes can take advantage of the a-priori knowledge of a contact plan comprising forthcoming communication opportunities. However, the design of such a plan needs to consider available spacecraft resources whose utilization can be optimized by exploiting the expected data which is largely foreseeable in typical Earth observation missions. In this work, we propose Traffic-Aware Contact Plan (TACP): a novel contact plan design procedure based on a Mixed Integer Linear Programming (MILP) formulation which exploits SSNs predictable properties in favor of delivering efficient and implementable contact plans for spaceborne DTNs. Finally, we analyze a low orbit SSN case study where TACP outperforms existing mechanisms and proves to be of significant impact on enhancing the delivery of sensed data from future space networks.Fil: Fraire, Juan Andres. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; ArgentinaFil: Madoery, Pablo Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Estudios Avanzados En Ingeniería y Tecnología. Universidad Nacional de Córdoba. Facultad de Ciencias exactas Físicas y Naturales. Instituto de Estudios Avanzados En Ingeniería y Tecnología; ArgentinaFil: Finochietto, Jorge Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Estudios Avanzados En Ingeniería y Tecnología. Universidad Nacional de Córdoba. Facultad de Ciencias exactas Físicas y Naturales. Instituto de Estudios Avanzados En Ingeniería y Tecnología; Argentin