A Source Routing Algorithm Based on CGR for DTN-Nanosatellite Networks

The number of nanosatellites orbiting around the Earth is increasing year after year. Nanosatellite constellations can be deployed to cover even larger areas. However, data exchange among nanosatellites is not trivial, especially due to the required hardware components related to the limited size and weight. Moreover, in some cases, contacts between nanosatellites and ground stations cannot always be guaranteed. The Delay and Disruption Tolerant Networking (DTN) paradigm allows storing data in nanosatellite and ground station buffers until the contact with the next hop is available. Routing in this kind of network is a crucial aspect. Delivery times are larger compared to a \u201cclassical\u201d network due to the time that data have to wait inside intermediate node buffers and to the limitation of available resources, especially on-board nanosatellites. The adoption of a smart routing strategy can contribute relieving this gap. In this paper, we propose S-CGR, a Source routing algorithm based on the Contact Graph Routing (CGR). It computes a routing path from source to destination nodes for each bundle, which is the data unit in DTN networks. S-CGR considers static and known a priori information about contacts (begin times, end times, and overall contact volumes) and dynamic information about nanosatellite buffer occupancies and available contact volumes. The complete source/destination paths are stored in the bundles. Intermediate nodes read the routin

Nanosatellite-5G Integration in the Millimeter Wave Domain: A Full Top-Down Approach

This paper presents a novel network architecture for an integrated nanosatellite (nSAT)-5G system operating in the millimeter-wave (mmWave) domain. The architecture is realized adopting a delay/disruption tolerant networking (DTN) approach allowing end users to adopt standard devices. A buffer aware contact graph routing algorithm is designed to account for the buffer occupancy of the nSATs and for the connection planning derived from their visibility periods. At the terrestrial uplink, a coded random access is employed to realize a high-capacity interface for the typically irregular traffic of 5G users, while, at the space uplink, the DTN architecture is combined with the contention resolution diversity slotted Aloha protocol to match the recent update of the DVB-RCS2 standard. To achieve a reliable testing of the introduced functionalities, an accurate analysis of the statistic of the signal to interference-plus-noise ratio and of the capture probability at each mmWave link is developed by including interference, shadowing, fading, and noise. The application of the designed architecture to data transfer services in conjunction with possible delay reduction strategies, and an extension to inter-satellite communication, are finally presented by estimating the resulting loss/delay performance through a discrete-time discrete-event platform based on the integration of Matlab with Network Simulator 3

Experimental Evaluation of On-Board Contact-Graph Routing Solutions for Future Nano-Satellite Constellations

Hardware processing performance and storage capability for nanosatellites have increased notably in recent years. Unfortunately, this progress is not observed at the same pace in transmission data rate, mostly limited by available power in reduced and constrained platforms. Thus, space-to-ground data transfer becomes the operations bottleneck of most modern space applications. As channel rates are approaching the Shannon limit, alternative solutions to manage the data transmission are on the spot. Among these, networked nano-satellite constellations can cooperatively offload data to neighboring nodes via frequent inter-satellite links (ISL) opportunities in order to augment the overall volume and reduce the end-to-end data delivery delay. Nevertheless, the computation of efficient multi-hop routes needs to consider not only present satellite and ground segments as nodes, but a non-trivial time dynamic evolution of the system dictated by orbital dynamics. Moreover, the process should properly model and rely on considerable amount of available information from node’s configuration and network status obtained from recent telemetry. Also, in most practical cases, the forwarding decision shall happen in orbit, where satellites can timely react to local or in-transit traffic demands. In this context, it is appealing to investigate on the applicability of adequate algorithmic routing approaches running on state-of-the-art nanosatellite on-board computers. In this work, we present the first implementation of Contact Graph Routing (CGR) algorithm developed by the Jet Propulsion Laboratory (JPL, NASA) for a nanosatellite on-board computer. We describe CGR, including a Dijkstra adaptation operating at its core as well as protocol aspects depicted in CCSDS Schedule-Aware Bundle Routing (SABR) recommended standard. Based on JPL’s Interplanetary Overlay Network (ION) software stack, we build a strong baseline to develop the first CGR implementation for a nano-satellites. We make our code available to the public and adapt it to the GomSpace toolchain in order to compile it for the NanoMind A712C on-board flight hardware based on a 32-bit ARM7 RISC CPU processor. Next, we evaluate its performance in terms of CPU execution time (Tick counts) and memory resources for increasingly complex satellite networks. Obtained metrics serve as compelling evidence of the polynomial scalability of the approach, matching the predicted theoretical behavior. Furthermore, we are able to determine that the evaluated hardware and implementation can cope with satellite networks of more than 120 nodes and 1200 contact opportunities

Small satellites and CubeSats: survey of structures, architectures, and protocols

The space environment is still challenging but is becoming more and more attractive for an increasing number of entities. In the second half of the 20th century, a huge amount of funds was required to build satellites and gain access to space. Nowadays, it is no longer so. The advancement of technologies allows producing very small hardware components able to survive the strict conditions of the outer space. Consequently, small satellites can be designed for a wide set of missions keeping low design times, production costs, and deployment costs. One widely used type of small satellite is the CubeSat, whose different aspects are surveyed in the following: mission goals, hardware subsystems and components, possible network topologies, channel models, and suitable communication protocols. We also show some future challenges related to the employment of CubeSat networks

Antenna and Random Access Solutions for nano-satellite and 5G networks operating in the millimiter-wave domain

L\u2019obiettivo di questa tesi \ue8 la discussione di soluzioni per reti satellitari basate su nano-satelliti e reti 5G, operanti in onde millimetriche. I contributi originali di questo lavoro interessano due settori che ricoprono un ruolo chiave nel contesto delle comunicazioni digitali ad alta velocit\ue0 e alta capacit\ue0: i meccanismi di condivisione del mezzo trasmissivo basati sull\u2019accesso casuale e le antenne a schiera riconfigurabili e compatte. I risultati ottenuti in questi due ambiti sono poi applicati in un\u2019architettura di rete che integra sistemi 5G terrestri e una costellazione di nanosatelliti in orbita bassa. Le comunicazioni satellitari sono sempre pi\uf9 parte integrante della vita quotidiana. Negli ultimi anni, si \ue8 registrata una crescita notevole dei piccoli satelliti (da 1 a 100 kg), sia in termini di tecnologia, che di frequenza di utilizzo. Non solo vengono lanciati in gran numero, ma si \ue8 iniziato ad utilizzarli in costellazioni da diverse decine di unit\ue0. Questa attivit\ue0 \ue8 l\u2019indicatore di una prospettiva ormai prossima: gli sviluppi nel settore dell\u2019Information and Communication Technology hanno avviato diverse iniziative che puntano ad utilizzare megacostellazioni di satelliti come reti per la fornitura di servizi di comunicazione a banda larga. Lo sfruttamento delle onde millimetriche rappresenta quindi un punto cardine per soddisfare la crescente richiesta di capacit\ue0 dei sistemi radio di prossima generazione. Inoltre, lo scenario che ne risulta \ue8 tale da richiedere una connettivit\ue0 completa, cos\uec che ogni satellite operi come un nodo di rete a tutto tondo, con possibilit\ue0 di collegamento tra la terra e lo spazio, e da satellite a satellite. In tale contesto, il ricorso a moderne tecniche di accesso casuale \ue8 particolarmente indicato. Negli ultimi anni si \ue8 assistito a un rinnovato interesse per i protocolli di tipo Aloha, grazie alla possibilit\ue0 di dotare i ricevitori di sistemi di cancellazione dell\u2019interferenza. A tale proposito, viene presentato un nuovo algoritmo che affianca alla cancellazione iterativa di interferenza lo sfruttamento dell\u2019effetto cattura, tenendo al tempo stesso presente la possibile non idealit\ue0 della cancellazione, e quindi la presenza di un residuo. Le sue prestazioni sono confrontate con i metodi attualmente adottati negli standard, mostrando un miglioramento del throughput pari al 31%. Viene inoltre presentata la sintesi di un\u2019antenna a schiera operante in banda Ka adatta per l\u2019uso su nanosatelliti. La schiera risultante offre interessanti benefici in termini di larghezza di banda, polarizzazione e versatilit\ue0, essendo possibile un utilizzo dual-task (downlink verso terra e collegamentointersatellitare). I risultati cos\uec ottenuti sono poi utilizzati per dimostrare, in un simulatore tempo discreto ed evento discreto, le prestazioni ottenibili da un\u2019architettura di rete integrante segmenti di rete radiomobile 5G con una dorsale costituita da una costellazione di nanosatellti. Il simulatore si avvale inoltre di un modello teorico per valutare l\u2019impatto della distribuzione geometrica dei nodi interferenti su una comunicazione in onde millimetriche di tipo line-of-sight. Tale modello, validato con simulazioni di tipo Monte Carlo, contempla i diagrammi di radiazione delle antenne e i recenti modelli di canale in onde millimetriche, che tengono in considerazione rumore, dispersione angolare, fading e bounded path loss. Sono state ricavate delle formulazioni analitiche per la distribuzione della potenza di rumore e interferenza, che consentono di valutare in forma chiusa la probabilit\ue0 di cattura. Tale impostazione \ue8 stata infine usata per discutere gli effetti dell\u2019interferenza sulla capacit\ue0 di Shannon di un collegamento in uplink operante in onde millimetriche, prendendo in considerazione delle condizioni realistiche per il canale

Implementing Delay-Tolerant Networking at Morehead State University

A thesis presented to the faculty of the College of Science at Morehead State University in partial fulfillment of the requirements for the Degree of Master of Science by Nathaniel J. Richard on April 28, 2017

Prediction-enhanced Routing in Disruption-tolerant Satellite Networks

This thesis introduces a framework for enhancing DTN (Delay-/Disruption-Tolerant Networking) routing in dynamic LEO satellite constellations based on the prediction of contacts. The solution is developed with a clear focus on the requirements imposed by the 'Ring Road' use case, mandating a concept for dynamic contact prediction and its integration into a state-of-the-art routing approach. The resulting system does not restrict possible applications to the 'Ring Road,' but allows for flexible adaptation to further use cases. A thorough evaluation shows that employing proactive routing in concert with a prediction mechanism offers significantly improved performance when compared to alternative opportunistic routing techniques

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

A novel dissemination protocol to deploy opportunistic services in federated satellite systems

The Earth Observation community is demanding new satellite applications that cover the need of monitoring different areas with high spatial resolution and short revisit times. These applications will generate huge amounts of data, and thus improvements in the downlink capacity are mandatory. Distributed Satellite Systems have emerged as a moderate-risk and cost-effective solution to meet these new requirements. These systems are groups of satellites that share a global and common objective. One of these systems are the Federated Satellite Systems, which rely on the collaboration between satellites that share unused resources, such as memory storage, computing capabilities, or downlink opportunities. In the same context, the Internet of Satellites paradigm expands the FSS concept to a multi-hop scenario, without predefining a satellite system architecture, and deploying temporal satellite networks. The basis of both concepts is the offer of unused satellite resources as services, being necessary that satellites notify their availability to other satellites that composes the system. This work presents the Opportunistic Service Avaliability Dissemination Protocol, which allows a satellite to publish an available service to be consumed by others. Details of the protocol behavior, and packet formats are presented as part of the protocol definition. Additionally, without loss of generality, the protocol has been verified in a realistic scenario composed of Earth Observation satellites, and the Telesat mega-constellation as a network backbone. The achieved results demonstrate the benefits of using the proposed protocol by doubling the downloaded data in some cases.This work was supported in part by the ’’CommSensLab’’ Excellence Research Unit Maria de Maeztu Ministerio de asuntos Económicos y transformación digital (MINECO) under Grant MDM-2016-0600; in part by the Spanish Ministerio de Ciencia e Innovación (MICINN) and European Union - European Regional Development Fund (EU ERDF) project ’’Sensing with pioneering opportunistic techniques‘‘ under Grant RTI2018-099008-B-C21; in part by the Agència de Gestió d’Ajuts Universitaris i de Recerca (AGAUR)—Generalitat de Catalunya (FEDER) under Grant FI-DGR 2015; and in part by the Secretaria d’Universitats i Recerca del Departament d’Empresa i Coneixement de la Generalitat de Catalunya under Grant 2017 SGR 376 and Grant 2017 SGR 219.Peer ReviewedPostprint (published version