Internet of Satellites (IoSat): an interconnected space paradigm

During the last years the space has been populated by Distributed Satellite Systems, which some of them have started to implement Inter-Satellite Communication. However, current solutions are composed of a unique mission and homogeneous spacecrafts or a combination of them. This actually limits their use in the so-called “Federated Satellite Systems” that proposes the interconnection of heterogeneous spacecrafts in order to establish a mission collaboration whenever the resources are not used for the primary mission goal. This point-to-point proposal has some limitations that can be addressed in a multi-hop platform, i.e. a network. Current satellite network proposals, such as Space Internet or Heterogeneous Spacecraft Network, propose the creation of a common network backbone which provides connectivity for future missions. However, this approach supposes huge maintenance and deployment costs. This work presents a new interconnected space paradigm based on a more peer-to-peer architecture: Internet of Satellites. This new paradigm promotes the creation of sporadic networks, called Inter Satellite Networks, which provide the required communication means to deploy Federated Satellite Systems for multi-hop cases.Peer ReviewedPostprint (published version

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

Assessment of satellite contacts using predictive algorithms for autonomous satellite networks

Upcoming Low Earth Orbit Satellite Networks will provide low-latency and high downlink capacity necessary for future broadband communications and Earth Observation missions. This architecture was proposed at the beginning of the 90’s, although it has just recently re-gained popularity thanks to the so-called Mega-Constellations. This network is composed of satellites that have Inter-Satellite Links (ISL) to communicate between them. Due to the satellite motion, an ISL is a temporal contact between two satellites characterized by a lifetime in which the communication remains feasible. The determination of a route between distant satellites is a challenging problem in this context. However, the satellite follows a well-known deterministic orbit trajectory, being feasible the prediction of its position by propagating a trajectory model over time. The Contact Graph Routing protocol uses this feature to determine the evolution of the routes by pre-computing on-ground a planning of the satellite contacts. This centralized ground-dependent solution cannot be directly applied in the Internet of Satellites paradigm, which proposes the autonomous deployment of heterogeneous satellite networks without pre-assuming any specific satellite system architecture. Following this concept, the present work proposes a distributed algorithm by which a satellite predicts neighbor contacts, and generates a global contact plan without trajectory propagation. To achieve this solution, an ISL has been modeled as a “close approach” between two satellites, which is characterized by their relative motion. The present work details the predictive algorithm, and evaluates its performance in two scenarios with a hybrid satellite constellation and a mega-constellation.This work was supported in part by the CommSensLab Excellence Research Unit Maria de Maeztu (MINECO) under GrantMDM-2016-0600, in part by the Spanish Ministerio MICINN and EU ERDF Project (Sensing With Pioneering Opportunistic Techniques) under Grant RTI2018-099008-B-C21, in part by the AGAUR—Generalitat de Catalunya (FEDER) under Grant FI-DGR 2015, and in partby the Secretaria d’Universitats i Recerca del Departament d’Empresa i Coneixement de la Generalitat de Catalunya under Grant 2017 SGR 376Peer ReviewedPostprint (published version

FSSCat Mission description and first scientific results of the FMPL-2 onboard 3CAT-5/A

FSSCat, the “Federated Satellite Systems/ 3 Cat-5” mission was the winner of the 2017 ESA S^3 (Sentinel Small Satellite) Challenge and overall winner of the Copernicus Masters competition. FSSCat consists of two 6 unit cubesats carrying on board UPC's Flexible Microwave Payload - 2 (FMPL-2), an L-band microwave radiometer and GNSS-Reflectometer implemented in a software defined radio, and Cosine's HyperScout-2 visible and near infrared + thermal infrared hyperspectral imager, enhanced with PhiSat-1, a on board Artificial intelligence experiment for cloud detection. Both spacecrafts include optical and UHF inter-satellite links technology demonstrators, provided by Golbriak Space and UPC, respectively. This paper describes the mission, and the main scientific results of the FMPL-2 obtained during the first three months of the mission, notably the sea ice concentration and thickness, and the downscaled soil moisture products over the Northern hemisphere.This work was supported by 2017 ESA S 3 challenge and Copernicus Masters overall winner award (“FSSCat” project) and ESA project “FSSCat Validation Experiment in MOSAIC”, by the Spanish Ministry of Science, Innovation and Universities, "Sensing with Pioneering Opportunistic Techniques" SPOT, grant RTI2018-099008- BC21/AEI/10.13039/501100011033, and by the Unidad de Excelencia Maria de Maeztu MDM-2016-0600.Peer ReviewedArticle signat per 25 autors/es: A. Camps 1,2; J.F. Munoz‐Martin 1; J.A. Ruiz‐de‐Azua 1,2; L. Fernandez 1; A. Perez-Portero 1; D. Llavería 1; C. Herbert 1; M. Pablos 3; A. Golkar 4,1; A. Gutiérrrez 5; C. António 5; J. Bandeiras 5; J. Andrade 5; D. Cordeiro 5; S. Briatore 4,6; N. Garzaniti 4,6; F. Nichele 7; R. Mozzillo 7; A. Piumatti 7; M. Cardi 7; M. Esposito 8; B. Carnicero Dominguez 9; M. Pastena 9; G. Filippazzo 10; A. Reagan 10 // 1. Universitat Politècnica de Catalunya, Barcelona, Spain; 2. Institut d’Estudis Espacials de Catalunya, Barcelona, Spain; 3. Institut de Ciències del Mar (ICM-CSIC) & Barcelona Expert Center (BEC) on Remote Sensing, Barcelona, Spain; 4. Skolkovo Institute of Science and Technology, Moscow, Russia; 5. Deimos Eng., Lisbon, Portugal; 6. Golbriak Space, Tallin, Estonia; 7. Tyvak International, Torino, Italy; 8. Cosine, Oosteinde, The Netherlands; 9. ESA ESTEC, Noordwijk, The Netherlands; 10. ESA ESRIN, Frascati, ItalyPostprint (author's final draft

3 Cat-4 mission, 1-Unit CubeSat for earth observation: Evaluation on the qualification and production during Phase D

The 3Cat-4 mission is a 1-unit CubeSat platform that serves as a technology demonstrator and educational platform for students at Universitat Politècnica de Catalunya (UPC). Promoted by the UPC Nanosatellite and Payload Laboratory (UPC NanoSatLab), the most notable subsystems that innovate in the nanosatellite scenario are (1) the Flexible Microwave Payload - 1 (FMPL-1) [1], a cost-effective payload to execute Global Navigation Satellite System Reflectometry (GNSS-R), and L-band microwave radiometry experiments using a commercial off-the-shelf (COTS) software-defined radio (SDR) and (2) the Nadir Antenna Deployment Subsystem (NADS) [2], an in-orbit deployable high-directivity antenna used by Earth Observation (EO) payloads. This paper presents the findings of the 3Cat-4 mission during Phase D, the qualification and production phase of the project. Since the publication of the first introductory work for this mission in 2019[3], several sections of the subsystems have been redesigned and upgraded to correct previous design flaws or to meet new requirements. In addition, this paper addresses the educational perspective of this mission, analyzing its performance and usefulness in the aforementioned subject

Deployment mechanism for an L-Band Helix antenna on-board the 3Cat-4 1U CubeSat

Earth Observation (EO) is key for climate and environmental monitoring at global level, and in specific regions where the effects of global warming are more noticeable, such as in polar regions, where ice melt is also opening new commercial maritime routes. Soil moisture is also useful for agriculture and monitoring the advance of desertification, as well as biomass and carbon storage. Global Navigation Satellite System - Reflectometry (GNSS-R) and L-band microwave Radiometry are passive microwave remote sensing techniques that can be used to perform these types of measurements regardless of the illumination and cloud conditions, and -since they are passive- they are well suited for small satellites, where power availability is a limiting factor. GNSS-R was tested from space onboard the UK-DMC and the UK TechDemoSat-1, and several missions have been launched using GNSS-R as main instrument, as CyGNSS, BuFeng-1, or the FSSCAT [1] mission. These missions aim at providing soil moisture [2], ocean wind speed [3], and flooding mapping of the Earth. L-band microwave radiometry data has also been retrieved from space with SMOS and SMAP missions, obtaining sea ice thickness, soil moisture, and ocean salinity data [4]. The 3Cat-4 mission was selected by the ESA Academy "Fly your Satellite" program in 2017. It aims at combining both GNSS-R and L-band Microwave Radiometry at in a low-power and cost-effective 1-Unit (1U) satellite. Moreover, the 3Cat-4 can also detect Automatic Identification System (AIS) signals from vessels. The single payload is the Flexible Microwave Payload 1 (FMPL-1) [5] that performs the signal conditioning and signal processing for GNSS-R, L-Band microwave radiometry and AIS experiments. The spacecraft has three payload antennas: (1) a VHF monopole for AIS signals; (2) an uplooking antenna for the direct GPS signals; (3) a downlooking antenna that captures reflected GPS signals, and for the Microwave Radiometer. The downlooking antenna is a deployable helix antenna called the Nadir Antenna and Deployment Subsystem (NADS) which has a volume of less than 0,3U when stowed, achieving an axial length of more than 500 mm when deployed. As part of this mission, the design of the NADS antenna, its RF performance, as well as the environmental tests performed in terms of structural and thermal space conditions will be presented

Contribution to the development of autonomous satellite communications networks : the internet of satellites

Aplicat embargament des de la data de defensa fins al dia 28 de febrer de 2021The space is experiencing a revolution due to the em ergence of satellite services to satisfy environmental, socio-econom ic, and geo-political demands. Earth Observation satellite systems have become dependable resources for climate monitoring, modern agriculture, and other applications. The 5G incursion in the aerospace domain has promoted the satellites as promising platforms to achieve global coverage, and cope the limitations of ground facilities. These demands can be summarized in two system requirements: (1) increase of data transfer capacity, and (2) decrease of end-to-end com m unications latency. Distributed Satellite Systems have emerged as an effective solution of m ultiple satellites operating simultaneouslyto satisfycommon requirements. Federated Satellite Systems are serious candidates to exploit the potential of distributed architectures by establishing opportunistic collaborations among satellites to share unallocated resources. These collaborations, called federations, allows to conceive the space as a cloud in which satellites leverage from other resources to improve their performance. The successive investigations have been centered on developing novel federation technologies. However, multiple design aspects are still open fields of study, such as the development of communications capabilities to establish these federations. This dissertation contributes to fill this gap bydefining mechanisms to deploy a network infrastructure for this purpose. A networked environment in which satellites are able to establish sporadically, and opportunisticallyfederations has been discussed. This context is called the Internet of Satellites paradigm, and prometes the temporal deployment of inter-satellite networks, composed of heterogeneous satellites. This feature---with satellite motion--­poses a challenge on the definition of end-to-end communications routes composed of intermediate satellites. Areview of current routing protocols from other satellite networks is conducted to identify the ideal protocol for these dynam ic networks. The outcome remarks the need to combine capabilities from different domains to achieve the desired performance. Among them, the capabilityto predict future inter-satellite links becomes crucial to mitigate the fragmentation of the network. With this prem ise in mind, this dissertation presents a predictive protocol that perform s the estimation of these inter-satellite contacts in a distributed manner. This new satellite capability may support the routing protocol by allowing the estimation of future routes as a sequence of satellite contacts over time. The research presented in this dissertation also tackles other questions that remained unanswered: How can satellites be aware of the available resources offered by other satellites? What are the necessary mechanisms to deploy a federation? A software stack with two protocols to deal with this technology gap has been developed. The Opportunistic Service Availability Dissem ination Protocol allows notifying the services that are available in a satellite, while the Federation Deploym ent Control Protocol form alizes the rules to establish and m anage a federation. The application of these protocols considerably enhancded the capabilityof the satellite system to download data, becom ing thus enablers of future satellite m issions. The achieved perform anee has motivated the developm ent of a dedicated system. 11 has been named Federated Satellite Systems Experiment payload, and includes a communications device to create inter-satellite links. This system has been verified in a stratospheric balloon campaign, and integrated in a CubeSat miss ion. This dissertation discusses the results of the campaign, which emphasize the benefits and viabilityof this implementation. We expect that the contributions of this dissertation mayencourage to keep investigating on this inter-satellite communications for satellite federations.L'espai esta experimentant! una revolució degut a l'aparició de serveis per satèl·lit que satisfan les noves demandes ambientals, socials i geo-polítiques. Els sistemes de satèl·lits per observar la Terra han esdevingut recursos essencials per el control del clima, !'agricultura moderna, i altres aplicacions. L'entrada del 5G en el sector aeroespacial ha promogut els satèl·lits com plataformes per aconseguir una cobertura global. Aquestes necessitats poden ser classificades en dos requeriments de sistema: (1) L'augment de la capacitat per transferir dades, i (2) la reducció de la latència en les comunicacions d'extrem-a-extrem. Els sistemes distribuïts de satèl·lits han esdevingut una solució efectiva amb múltiples satèl·lits essent operats simultàniament per satisfer uns requeriments comuns. Els sistemes federats de satèl·lits són candidats prometedors per explotar el potencial de les arquitectures distribuïdes mitjançant col·laboracions oportunistiques entre satèl·lits per compartir recursos. Aquestes col·laboracions, anomenades federacions, permeten concebre l'espai com un entorn on els satèl·lits poden beneficiar-se dels recursos d'altres per millorar el seu funcionament. Les investigacions s'han central en desenvolupar noves tecnologies per aquestes federacions. No obstant, molts aspectes de disseny encara són punts oberts de recerca, com ara el desenvolupament de protocols de comunicació per establir aquestes federacions. Aquesta tesina contribueix definint mecanismes que permeten desplegar una infraestructura en xarxa per establir federacions. A més a més, es discuteix sobre aquest context interconnectat on els satèl·lits poden establir esporàdicament i oportunísticament les federacions. Aquest escenari s'ha anomenat la Internet dels Satèl·lits, i promou els desplegament temporal de xarxes entre satèl·lits heterogenis. Aquesta característica, amb el moviment dels satèl·lits, suposa un repte en la definició de rutes entre extrems formades per satèl·lits intermitjos. Una revisió de protocols d'enrutament actuals d'altres xarxes de satèl·lits s'ha realitzat per identificar el protocol ideal per aquest tipus de xarxa dinàmica. El resultat remarca la necessitat de combinar capacitats de diferents dom in is per aconseguir el funcionament desitjat. Entre aquestes, la capacitat de preveure futurs enllaços entre satèl·lits esdevé crucial per mitigar la fragmentació de la xarxa. Amb aquesta premissa, aquesta tesina presenta un protocol predictiu que estima aquests contactes entre satèl·lits de forma distribuïda. Aquesta nova capacitat pot complementar el protocol d'enrutament mitjançant l'estimació de futures rutes com seqüències of contactes de satèl·lits a través del temps. La recerca presentada en aquesta tesina també respon altres preguntes que no s'havien res post encara: Com els satèl·lits poden descobrir els recursos disponibles en la xarxa? Quins són els mecanismes necessaris per establir i mantenir una federació? Una pila de protocols per cobrir aquesta necessitat tecnològica ha sigut desenvolupat. El protocol de dispersió de la disponibilitat de serveis oportunístics permet notificar els serveis disponibles en un satèl·lit, mentre que el protocol desplegament i control de federacions s'encarrega d'establir i gestionar les federacions. L'aplicació d'aquests protocols considerablement van realçar la capacita! del sistema de satèl·lit per descarregar dades, esdevenint així potenciadors de futures missions. Aquests resultats han motivat el desenvolupament d'un sistema dedica!, que inclou un dispositiu de comunicacions per crear enllaços entre satèl·lit. Aquest sistema ha estat verifica! en una campanya de globus estratosfèrics, i ha sigut integral en una missió de CubeSats. Aquesta dissertació presenta els resultats de la campanya, els quals emfasitzen els profits i viabilitat d'aquesta implementació.Postprint (published version

Control Activo en AFDX y Modelización ARINC 653

El proyecto se basa en un análisis sobre la tecnología AVB (Audio/Video Bridging) para ser capaces de caracterizar el delay máximo y así el comportamiento en situaciones críticaThe presented work is oriented on explain the experience of the investigation performed on the embedded systems field. Concretely, the investigation is composed of two standards: ARINC 664 and ARINC 653. The investigation about the standard ARINC 664 Part 7, called Avionic Full Duplex Switched Ethernet (AFDX), is oriented on the improvement of the bandwidth utilization using an active control system. AFDX is a technology that allows guaranteeing an expected behaviour, an important characteristic for avionic real-time applications. In order to reinforce the quality of service, the standard define the concept of Virtual Link (VL) which determine a unidirectional logic point-to-point connection. The VL transmission is limited by the Bandwidth Allocation Gap (BAG), which indicates the minimum period of time between two consecutives frames. Considering that only specific values of BAG are accepted while the application period is arbitrary, the utilization of the bandwidth becomes small. In addition, owing to the asynchronous nature of AFDX protocol, the jitter degrades the determinism of the network, which constraints the use of critical applications. Therefore, the research has contribute a feedback system based on active control in order to avoid this problem. Concretely, two control loops have been presented. The first one, called Bandwidth Efficiency Control Loop (BECL), is oriented on maximizing the bandwidth utilization of the VL. The second one, called Jitter Stabilization Control Loop (JSCL), is used in order to stabilize the jotter on a predefined value. The second research subject, which is based on the standard ARINC 653, defines an optimization model to allocate and schedule different tasks which share the same resources inside a system. The utilization of the Integrate Modular Avionic (IMA) architecture is a technologic tendency in the avionic industry, thanks to its capacity for sharing time and space between different tasks. However, the combination of allocation and scheduling of tasks can be a complex problem. Therefore, a model that allows an automatic adjustment following a criteria has been developed. The model variables and constraints are formulated by lineal inequalities and equalities. Therefore, the problem can be solved in an efficient way by lineal programming algorithms. This experience has allowed me to go in depth in the embedded systems field, specifically in the AFDX network. Moreover, I have been able to apply the knowledge earn during my study in a real research situation. The result of this experience has been the production of two articles: • The article with the title Active Bandwidth Efficiency and Jitter Control for AFDX: A Network Calculus Approach has been presented as a draft for IEEE INFOCOM 2016 conference. • The article with the title A Modeling and Optimization of Simultaneous Partition Allocation and Schedule Design for Mixed-Criticality Systems has been presented as a draft for European Journal of Operational Research.El trabajo presentado tiene como objetivo explicar la experiencia en investigación sobre el dominio de los sistemas embarcados. Concretamente, la investigación se ha dividido en dos estándares: ARINC 664 y ARINC 653. La investigación sobre el estándar ARINC 664 Parte 7, conocido como Avionic Full Duplex Switched Ethernet (AFDX), ha estado orientada a la mejora de la utilización de los recursos, como por ejemplo el ancho de banda, mediante el uso de un sistema de control activo. AFDX es una tecnología que permite garantizar un comportamiento previsible, una característica importante para las aplicaciones aviónicas de tiempo-real. Para reforzar la calidad del servicio, el estándar define el concepto de Circuito Virtual (VL) que determina una conexión lógica de punto-a-punto y unidireccional. La transmisión del VL está limitada por el Bandwidth Allocation Gap (BAG), que indica el periodo mínimo de tiempo entre dos frames consecutivas. Considerando que ciertos valores específicos de BAG son autorizados al mismo tiempo que el periodo de la aplicación es arbitrario, la utilización del ancho de banda puede ser pequeña. Además, debido a que AFDX es un protocolo asíncrono, el jitter degrada el determinismo de la red, cosa que limita las aplicaciones críticas. Por ese motivo, la investigación ha aportado un sistema de feedback de control activo para evitar esta problemática. Concretamente, dos esquemas de control han estado definidos. El primero, llamado Bandwidth Efficiency Control Loop (BECL), tiene como objetivo maximizar el uso del ancho de banda en un VL. El segundo, llamado Jitter Stabilization Control Loop (JSCL), es usado para estabilizar el jitter sobre un valor predefinido. El segundo tema, el que se basa en la investigación del estándar ARINC 653, aporta un modelo de optimización para la distribución y la programación temporal de procesos (llamados tareas) que comparten los mismos recursos dentro de un sistema. El uso de la arquitectura Integrada Modular Aviónica (IMA) es una tendencia tecnológica de la industria de la aviación, gracias a la capacidad de compartir el tiempo i el espacio entre diferentes procesos. No obstante, combinar la distribución y la programación temporal de diferentes aplicaciones que comparten los mismos recursos dentro de una misma plataforma puede suponer un problema muy complejo. Para solucionar este problema, un modelo que permite el ajuste automático según un criterio de optimización ha sido desarrollado. Las variables i las restricciones del modelo son formulados mediante desigualdades y/o igualdades lineales. Por ese motivo, el problema puede ser solucionado de una forma eficiente mediante diferentes algoritmos de programación lineal. Esta experiencia me ha permitido profundizar en el dominio de los sistemas embarcados, sobretodo en la red AFDX. Además, he podido aplicar los conocimientos obtenidos durante mis estudios en una situación real de investigación. El resultado de esta experiencia ha sido la producción de dos artículos: • El artículo que tiene como título Active Bandwidth Efficiency and Jitter Control for AFDX: A Network Calculus Approach ha sido presentado como draft para la conferencia IEEE INFOCOM 2016. • El artículo que tiene como título A Modeling and Optimization of Simultaneous Partition Allocation and Schedule Design for Mixed-Criticality Systems ha sido presentado como draft para la revista European Journal of Operational Research.El treball presentat té com objectiu detallar l’experiència de recerca realitzada sobre el domini de sistemes embarcats. Concretament, la recerca ha estat dividida en dos estàndards: ARINC 664 i ARINC 653. La recerca sobre l’estàndard ARINC 664 Part 7, conegut com Avionic Full Duplex Switched Ethernet (AFDX), ha estat orientada a la millora de l’utilització dels recursos, com per exemple l’ample de banda, en utilitzant un sistema de control actiu. L’AFDX és una tecnologia que permet garantir comportements prévisibles, una propietat important per les aplicacions aviòniques de temps-real. Per enfortir la qualitat de server, l’extàndard defineix el concepte de Circuit Virtual (VL) que determina una conexió lògica de punt-a-punt i unidireccional. La transmissió del VL està limitada pel Bandwidth Allocation Gap (BAG), que indique el període mínim de temps entre dues frames consecutives. En considerant que certs valors específics del BAG són autoritzats al mateix temps quel període de l’aplicació és arbitrari, l'utilització de l’ample de bande pot ser petita. Ademés, degut a que l’AFDX és un protocol asíncron, el jitter degrada el determinisme de la xarxa, cosa que limita les aplicacions crítiques. Per aquest motiu, la recerca ha aportat un sistèma de feedback de control actiu per evitar aquesta problemàtica. Concretament, dos esquemes de control han estat definits. El primer, anomenat Bandwidth Efficiency Control Loop (BECL), té com objectiu maximitzar l’utilització de l’ample de bande sobre un VL. El segon, anomenat Jitter Stabilization Control Loop (JSCL), és utilitzat per estabilitzar el jitter en un valor predefinit. El segon tema, aquell que es basa en la recerca de l’estàndard ARINC 653, aporta un model d'optimisació per la distribució de particions i per la programació temporal de processus (anomenats tasques) que comparteixen els mateixos recursos dins del mateix sistema. L'utilització de l’arquitectura Integrada Modular Aviònica (IMA) és una tendència tecnològica dins la indústria de l’aviació, gràcies a la capacitat de compartir el temps i l’espai entre diferents processos. No obstant, combinar la distribució i la programació temporal d’aplicacions que comparteixen els mateixos recursos dins de la mateixa plataforma pot esdevenir un problema d’una gran complexitat. Per adreçar aquesta problématica, un model que permet l’ajustement automàtic segons un criteri d’optimització ha estat desenvolupat. Les variables i les restriccions del model sont totes formulades mitjançant inegalitats i/o égalitats lineals. Per aquest motiu, el problema pot ser resolt d’una forma eficient mitjançant diferents algoritmes de programació lineal. Aquesta experiència m’ha permès aprofondir en el domini de sistemes embarcats, sobretot en la xarxa AFDX. Ademés, he pogut aplicar els coneixements obtinguts durant els meus estudis en una situació real de recerca. Els resultats d’aquesta experiència han estat la producció de dos articles: • L'article que té com a títol Active Bandwidth Efficiency and Jitter Control for AFDX: A Network Calculus Approach ha estat lliurat com a draft per la conferència IEEE INFOCOM 2016. • L'article que té com a títol A Modeling and Optimization of Simultaneous Partition Allocation and Schedule Design for Mixed-Criticality Systems ha estat lliurat com a draft per la revista European Journal of Operational Research

Control Activo en AFDX y Modelización ARINC 653

El proyecto se basa en un análisis sobre la tecnología AVB (Audio/Video Bridging) para ser capaces de caracterizar el delay máximo y así el comportamiento en situaciones críticaThe presented work is oriented on explain the experience of the investigation performed on the embedded systems field. Concretely, the investigation is composed of two standards: ARINC 664 and ARINC 653. The investigation about the standard ARINC 664 Part 7, called Avionic Full Duplex Switched Ethernet (AFDX), is oriented on the improvement of the bandwidth utilization using an active control system. AFDX is a technology that allows guaranteeing an expected behaviour, an important characteristic for avionic real-time applications. In order to reinforce the quality of service, the standard define the concept of Virtual Link (VL) which determine a unidirectional logic point-to-point connection. The VL transmission is limited by the Bandwidth Allocation Gap (BAG), which indicates the minimum period of time between two consecutives frames. Considering that only specific values of BAG are accepted while the application period is arbitrary, the utilization of the bandwidth becomes small. In addition, owing to the asynchronous nature of AFDX protocol, the jitter degrades the determinism of the network, which constraints the use of critical applications. Therefore, the research has contribute a feedback system based on active control in order to avoid this problem. Concretely, two control loops have been presented. The first one, called Bandwidth Efficiency Control Loop (BECL), is oriented on maximizing the bandwidth utilization of the VL. The second one, called Jitter Stabilization Control Loop (JSCL), is used in order to stabilize the jotter on a predefined value. The second research subject, which is based on the standard ARINC 653, defines an optimization model to allocate and schedule different tasks which share the same resources inside a system. The utilization of the Integrate Modular Avionic (IMA) architecture is a technologic tendency in the avionic industry, thanks to its capacity for sharing time and space between different tasks. However, the combination of allocation and scheduling of tasks can be a complex problem. Therefore, a model that allows an automatic adjustment following a criteria has been developed. The model variables and constraints are formulated by lineal inequalities and equalities. Therefore, the problem can be solved in an efficient way by lineal programming algorithms. This experience has allowed me to go in depth in the embedded systems field, specifically in the AFDX network. Moreover, I have been able to apply the knowledge earn during my study in a real research situation. The result of this experience has been the production of two articles: • The article with the title Active Bandwidth Efficiency and Jitter Control for AFDX: A Network Calculus Approach has been presented as a draft for IEEE INFOCOM 2016 conference. • The article with the title A Modeling and Optimization of Simultaneous Partition Allocation and Schedule Design for Mixed-Criticality Systems has been presented as a draft for European Journal of Operational Research.El trabajo presentado tiene como objetivo explicar la experiencia en investigación sobre el dominio de los sistemas embarcados. Concretamente, la investigación se ha dividido en dos estándares: ARINC 664 y ARINC 653. La investigación sobre el estándar ARINC 664 Parte 7, conocido como Avionic Full Duplex Switched Ethernet (AFDX), ha estado orientada a la mejora de la utilización de los recursos, como por ejemplo el ancho de banda, mediante el uso de un sistema de control activo. AFDX es una tecnología que permite garantizar un comportamiento previsible, una característica importante para las aplicaciones aviónicas de tiempo-real. Para reforzar la calidad del servicio, el estándar define el concepto de Circuito Virtual (VL) que determina una conexión lógica de punto-a-punto y unidireccional. La transmisión del VL está limitada por el Bandwidth Allocation Gap (BAG), que indica el periodo mínimo de tiempo entre dos frames consecutivas. Considerando que ciertos valores específicos de BAG son autorizados al mismo tiempo que el periodo de la aplicación es arbitrario, la utilización del ancho de banda puede ser pequeña. Además, debido a que AFDX es un protocolo asíncrono, el jitter degrada el determinismo de la red, cosa que limita las aplicaciones críticas. Por ese motivo, la investigación ha aportado un sistema de feedback de control activo para evitar esta problemática. Concretamente, dos esquemas de control han estado definidos. El primero, llamado Bandwidth Efficiency Control Loop (BECL), tiene como objetivo maximizar el uso del ancho de banda en un VL. El segundo, llamado Jitter Stabilization Control Loop (JSCL), es usado para estabilizar el jitter sobre un valor predefinido. El segundo tema, el que se basa en la investigación del estándar ARINC 653, aporta un modelo de optimización para la distribución y la programación temporal de procesos (llamados tareas) que comparten los mismos recursos dentro de un sistema. El uso de la arquitectura Integrada Modular Aviónica (IMA) es una tendencia tecnológica de la industria de la aviación, gracias a la capacidad de compartir el tiempo i el espacio entre diferentes procesos. No obstante, combinar la distribución y la programación temporal de diferentes aplicaciones que comparten los mismos recursos dentro de una misma plataforma puede suponer un problema muy complejo. Para solucionar este problema, un modelo que permite el ajuste automático según un criterio de optimización ha sido desarrollado. Las variables i las restricciones del modelo son formulados mediante desigualdades y/o igualdades lineales. Por ese motivo, el problema puede ser solucionado de una forma eficiente mediante diferentes algoritmos de programación lineal. Esta experiencia me ha permitido profundizar en el dominio de los sistemas embarcados, sobretodo en la red AFDX. Además, he podido aplicar los conocimientos obtenidos durante mis estudios en una situación real de investigación. El resultado de esta experiencia ha sido la producción de dos artículos: • El artículo que tiene como título Active Bandwidth Efficiency and Jitter Control for AFDX: A Network Calculus Approach ha sido presentado como draft para la conferencia IEEE INFOCOM 2016. • El artículo que tiene como título A Modeling and Optimization of Simultaneous Partition Allocation and Schedule Design for Mixed-Criticality Systems ha sido presentado como draft para la revista European Journal of Operational Research.El treball presentat té com objectiu detallar l’experiència de recerca realitzada sobre el domini de sistemes embarcats. Concretament, la recerca ha estat dividida en dos estàndards: ARINC 664 i ARINC 653. La recerca sobre l’estàndard ARINC 664 Part 7, conegut com Avionic Full Duplex Switched Ethernet (AFDX), ha estat orientada a la millora de l’utilització dels recursos, com per exemple l’ample de banda, en utilitzant un sistema de control actiu. L’AFDX és una tecnologia que permet garantir comportements prévisibles, una propietat important per les aplicacions aviòniques de temps-real. Per enfortir la qualitat de server, l’extàndard defineix el concepte de Circuit Virtual (VL) que determina una conexió lògica de punt-a-punt i unidireccional. La transmissió del VL està limitada pel Bandwidth Allocation Gap (BAG), que indique el període mínim de temps entre dues frames consecutives. En considerant que certs valors específics del BAG són autoritzats al mateix temps quel període de l’aplicació és arbitrari, l'utilització de l’ample de bande pot ser petita. Ademés, degut a que l’AFDX és un protocol asíncron, el jitter degrada el determinisme de la xarxa, cosa que limita les aplicacions crítiques. Per aquest motiu, la recerca ha aportat un sistèma de feedback de control actiu per evitar aquesta problemàtica. Concretament, dos esquemes de control han estat definits. El primer, anomenat Bandwidth Efficiency Control Loop (BECL), té com objectiu maximitzar l’utilització de l’ample de bande sobre un VL. El segon, anomenat Jitter Stabilization Control Loop (JSCL), és utilitzat per estabilitzar el jitter en un valor predefinit. El segon tema, aquell que es basa en la recerca de l’estàndard ARINC 653, aporta un model d'optimisació per la distribució de particions i per la programació temporal de processus (anomenats tasques) que comparteixen els mateixos recursos dins del mateix sistema. L'utilització de l’arquitectura Integrada Modular Aviònica (IMA) és una tendència tecnològica dins la indústria de l’aviació, gràcies a la capacitat de compartir el temps i l’espai entre diferents processos. No obstant, combinar la distribució i la programació temporal d’aplicacions que comparteixen els mateixos recursos dins de la mateixa plataforma pot esdevenir un problema d’una gran complexitat. Per adreçar aquesta problématica, un model que permet l’ajustement automàtic segons un criteri d’optimització ha estat desenvolupat. Les variables i les restriccions del model sont totes formulades mitjançant inegalitats i/o égalitats lineals. Per aquest motiu, el problema pot ser resolt d’una forma eficient mitjançant diferents algoritmes de programació lineal. Aquesta experiència m’ha permès aprofondir en el domini de sistemes embarcats, sobretot en la xarxa AFDX. Ademés, he pogut aplicar els coneixements obtinguts durant els meus estudis en una situació real de recerca. Els resultats d’aquesta experiència han estat la producció de dos articles: • L'article que té com a títol Active Bandwidth Efficiency and Jitter Control for AFDX: A Network Calculus Approach ha estat lliurat com a draft per la conferència IEEE INFOCOM 2016. • L'article que té com a títol A Modeling and Optimization of Simultaneous Partition Allocation and Schedule Design for Mixed-Criticality Systems ha estat lliurat com a draft per la revista European Journal of Operational Research

Internet of Satellites (IoSat): an interconnected space paradigm

During the last years the space has been populated by Distributed Satellite Systems, which some of them have started to implement Inter-Satellite Communication. However, current solutions are composed of a unique mission and homogeneous spacecrafts or a combination of them. This actually limits their use in the so-called “Federated Satellite Systems” that proposes the interconnection of heterogeneous spacecrafts in order to establish a mission collaboration whenever the resources are not used for the primary mission goal. This point-to-point proposal has some limitations that can be addressed in a multi-hop platform, i.e. a network. Current satellite network proposals, such as Space Internet or Heterogeneous Spacecraft Network, propose the creation of a common network backbone which provides connectivity for future missions. However, this approach supposes huge maintenance and deployment costs. This work presents a new interconnected space paradigm based on a more peer-to-peer architecture: Internet of Satellites. This new paradigm promotes the creation of sporadic networks, called Inter Satellite Networks, which provide the required communication means to deploy Federated Satellite Systems for multi-hop cases.Peer Reviewe