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The integration of non-terrestrial networks into the 5G ecosystem is mainly driven by the possibility of provisioning service in remote areas. In this context, the advent of flying base stations at the low Earth orbit (LEO) will enable anywhere and anytime connectivity. To materialize this vision, it is of utmost importance to improve radio protocols with the aim of allowing direct satellite access. Bearing this aspect in mind, we present a new random access signal, which is based on the filter bank multicarrier (FBMC) waveform, and a computationally efficient detection scheme. The proposed solution outperforms the standardized access scheme based on single-carrier frequency division multiplexing (SC-FDM), by reducing out-of-band (OOB) emissions and reducing the missed detection probability in presence of very high carrier frequency offset (CFO), which is inherent to LEO satellite systems. The improvement is related to the fine frequency resolution of the detector and the use of pulse shaping techniques. Interestingly, the FBMC-based random access signal achieves a high level of commonality with 5G new radio, as the preamble generation method and the time-frequency allocation pattern can be kept unchanged. Concerning the practical implementation aspects, the complexity of the detector is similar in both SC-FDM and FBMC. This paper is part of the R+D+i project (PID2020-115323RB-C31) funded by MCIN/AEI/ 10.13039/501100011033. This work is supported by the grant from Spanish Ministry of Economic Affairs and Digital Transformation and the European union - NextGenerationEU (UNICO-5G I+D/AROMA3D-Space (TSI-063000-2021-70))

This paper presents an integrated network architecture combining a cell-free massive multiple-input multiple-output (CF-M-MIMO) terrestrial layout with a low Earth orbit satellite segment where the scalability of the terrestrial segment is taken into account. The main purpose of such an integrated scheme is to transfer to the satellite segment those users that somehow limit the performance of the terrestrial network. Towards this end, a correspondingly scalable technique is proposed to govern the ground-to-satellite user diversion that can be tuned to different performance metrics. In particular, in this work the proposed technique is configured to result in an heuristic that improves the minimum per-user rate and the sum-rate of the overall network. Simulation results serve to identify under which conditions the satellite segment can become an attractive solution to enhance users’ performance. Generally speaking, although the availability of the satellite segment always leads to an improvement of users’ rates, it is in those cases where the terrestrial CF-M-MIMO network exhibits low densification traits that the satellite backup becomes crucial. This work was supported in part by the Agencia Estatal de Investigación, Ministerio de Ciencia e Innovación (MCIN/AEI/10.13039/501100011033) through the R+D+i Project under Grant PID2020-115323RB-C32 and Grant PID2020-115323RB-C31; and in part by the Centre Tecnológic de Telecomunicacions de Catalunya Researchers through the Grant from the Spanish Ministry of Economic Affairs and Digital Transformation and the European Union-NextGenerationEU under Grant UNICO-5G I+D/AROMA3D-Hybrid TSI-063000-2021-71.

This paper investigates a dual satellite transmission scheme with coherent reception. The receiver has a single synchronization circuit and is locked to only one of the satellites. Beam-centric pre-compensation techniques are considered in the paper. The cooperation area in which coherent reception is feasible is characterized analytically. The application of precoding to the orthogonal time and frequency space (OTFS) waveform is considered to counteract the residual offsets, which result from the displacement of the receiver from the selected reference point. Numerical evaluations show that the dual satellite scheme improves the system spectral efficiency as well the link reliability in comparison with the single satellite transmission scheme. This paper is part of the R+D+i project (PID2020-115323RB-C31) funded by MCIN/AEI/ 10.13039/501100011033.

Aquest treball ha rebut finançament del programa europeu DISCOVERER (Disruptive Technologies for Very Low Earth Orbit Platforms, EC-H2020-737183) This thesis studies the complementarity of VLEO satellite technologies with existing solutions in the telecommunications market, both in the space and terrestrial sectors. All the characteristics and particularities of VLEO orbits are defined and explained in detail, showing advantages and disadvantages compared to traditional higher orbits. Study of the deployment of the satellite constellation concept within the New Space framework. Next, the business opportunities that can be generated by the introduction of VLEO technologies in the telecommunications market are studied, analysing the possible reshaping of each vertical market and how can they be most benefited. Finally, a business opportunity is proposed and qualitatively analysed in detail using the Value Proposition Canvas methodology.

Recently, there has been a paradigm shift in space missions. They no longer rely on a single satellite to achieve all the objectives of a mission. Responsibility is shared between devices that can communicate and share resources to achieve these objectives. This paradigm shift has increased the need to assess communication performance within FSS. Despite proposals for simulators and emulators to achieve this goal, none of them integrates the dynamics of satellites with their communications. This thesis presents two proposals and the implementation of one of them to extend the capabilities of the communication channel of the simulator developed by the NanoSat Lab of the UPC. Additionally, following the lines of the i2Cat Space Communications research group, a test bench is also presented to demonstrate the feasibility of a satellite contact emulator. As it will be demonstrated, developing such an emulator has not been possible. Finally, it is concluded that both parts of this thesis may converge. Thus, combining the possibilities offered by the current simulator with those available in the emulator under development. En el transcurso de los últimos años se ha observado un cambio en el paradigma en las misiones espaciales. Éstas ya no cuentan sólo con un único satélite que tenga que alcanzar todos los objetivos de una misión. Se reparte la responsabilidad entre diferentes dispositivos que son capaces de comunicarse y compartir recursos para alcanzar tales objetivos. De ese cambio de paradigma nace la necesidad de poder evaluar el comportamiento de las comunicaciones dentro de un FSS. A pesar de la existencia de simuladores y propuestas de emuladores para alcanzar tal objetivo, ninguno de ellos integra las dinámicas de los satélites con sus comunicaciones. En esta tesis, se presentan dos propuestas y la implementación de una de ellas para ampliar las capacidades del canal de comunicaciones del simulador desarrollado por NanoSat Lab de la UPC. Además, siguiendo las líneas del grupo de investigación de Comunicaciones Espaciales de i2Cat también se presenta un test-bed para demostrar la viabilidad de un emulador de contactos de satélites. Pues, como se va a demostrar, el desarrollador de uno como tal no ha sido posible. Por último, se concluirá que ambas partes de esta tesis puedan converger en algún momento combinando así las posibilidades que ofrece el actual simulador con las de un emulador que está en desarrollo. En el transcurs dels últims anys s’ha observat un canvi en el paradigma de les missions espacials. Aquestes ja no compten només d’un únic satèl·lit que hagi d’assolir tots els objectius d’una missió. Es reparteix la responsabilitat entre diferents dispositius els quals són capaços de comunicar-se i compartir recursos per tal d’assolir tals objectius. D’aquest canvi de paradigma neix la necessitat de poder avaluar el comportament de les comunicacions dins d’un FSS. Tot i l’existència de simuladors i propostes d’emuladors per assolir tal objectiu, cap d’ells integra les dinàmiques dels satèl·lits amb les seves comunicacions. En aquesta tesi, es presenten dues propostes i la implementació d’una d’elles per tal d’ampliar les capacitats del canal de comunicacions del simulador desenvolupat pel NanoSat Lab de la UPC. A més a més, seguint les línies del grup de recerca de Comunicacions Espacials d'i2Cat també es presenta un test-bed per tal de poder demostrar la viabilitat d’un emulador de contactes de satèl·lits. Doncs, com es demostrarà, el desenvolupant d’un com a tal no ha estat possible. Finalment, es conclourà que ambdues parts d'aquesta tesi puguin convergir en algun moment combinant així les possibilitat que ofereix l'actual simulador amb les d’un emulador que està en desenvolupament

We have recently been able to witness how large companies have set themselves the goal of launching fleets of hundreds or even thousands of satellites to offer different services. This new generation of satellites is marking a clear trend to reduce their size and cost. However, this also leads to increasingly demanding challenges and constraints that require innovative solutions in the design of small-size, high-capacity communications systems. The present work offers the complete process from the design, to the implementation and test of a communications system for PocketQube picosatellites. The proposed solution benefits from LoRa technology, and includes both the hardware part of the communications subsystem and software for its configuration and operation according to the defined protocol. Finally, this project has been designed and integrated, and its compatibility and cooperation with the rest of the subsystems has been tested, for the PoCAT picosatellites developed at the UPC NanoSat Lab. Recientemente hemos podido presenciar como grandes compañías se han marcado el objetivo de lanzar flotas de cientos o incluso miles de satélites para ofrecer diferentes servicios. Esta nueva generación de satelites está marcando una clara tendencia a reducir el tamaño y coste de éstos. Sin embargo, esto también conlleva retos y restricciones cada vez más exigentes que necesitan soluciones inovadoras en el diseño de sistemas de comunicaciones de tamaño reducido y alta capacidad. El presente trabajo ofrece el proceso completo desde el diseño, pasando por la implemetación y test, de un sistema de comunicaciones para picosatelites PocketQube. La solución propuesta se beneficia de la tecnología LoRa, y comprende tanto la parte de hardware del subsistema de comunicaciones, como el software para su configuración y funcionamiento según el protocolo definido. Finalmente, este proyecto ha sido diseñado e integrado, y se ha probado su compatibilidad y cooperación con el resto de subsistemas, para los picosatellites PoCAT desarrollados por el UPC NanoSat Lab. Recentment, hem pogut presenciar com grans companyies s'han marcat l'objectiu de llançar flotes de centenars o fins i tot milers de satèl·lits per oferir diferents serveis. Aquesta nova generació de satèl·lits està marcant una clara tendència a reduir-ne la mida i el cost. No obstant, això també comporta reptes i restriccions cada vegada més exigents que necessiten solucions innovadores en el disseny de sistemes de comunicacions de mida reduïda i alta capacitat. Aquest treball ofereix el procés complet des del disseny, passant per la implementació i test, d'un sistema de comunicacions per a picosatèl·lits PocketQube. La solució proposada es beneficia de la tecnologia LoRa, i comprèn tant la part de hardware del subsistema de comunicacions, com el software per a la seva configuració i funcionament segons el protocol definit. Finalment, aquest projecte ha estat dissenyat i integrat, i s’ha provat la seva compatibilitat i cooperació amb la resta de subsistemes, pels picosatèl·lits PoCAT desenvolupats per l'UPC NanoSat Lab.

UPC NanoSat Lab is a laboratory located in the Universitat Politècnica de Catalunya, which is focused on the design and development of nano and picosatellite spacecrafts. This type of platforms have significant limitations in dimensions and structure. Nevertheless, due to its reduced cost, there is a high momentum as many companies and universities are investing their resources in innovative applications for Earth observation and communications. This thesis is part of a UPC NanoSat Lab project for the IEEE Geoscience and Remote Sensing Society called "Open PocketQube Kit". It aims at developing different educational PocketQubes, a type of picosatellite with a 5 cm cube size, which will be integrated in the 3Cat-8 mission. Precisely, this final degree thesis is focused on the design and implementation of the electrical power supply for these spacecrafts as well as a thermal analysis study for the whole of the structure. El UPC NanoSat Lab es un laboratorio de la Universidad Politécnica de Cataluña, que se centra en el diseño y desarrollo de nano y picosatélites. Este tipo de plataformes tienen limitaciones significativas en dimensiones y potencia. Sin embargo, debido a su coste reducido, existe un impulso creciente por parte de muchas empresas y universidades que estan invirtiendo sus recursos en aplicaciones innovadoras de observación terrestre y comunicaciones. Este trabajo de final de grado forma parte de un proyecto del UPC NanoSat Lab para la IEEE Geoscience and Remote Sensing Society titulado "Open PocketQube Kit" que tiene como objectivo desarrollar diferentes PocketQubes educativos, un tipo de picosatélites con forma de cubo de 5 cm de tamaño, los cuales irán integrados dentro de la misión del 3Cat-8. Precisamente, este trabajo de final de grado está centrado en el diseño e implementación del subsistema de alimentación eléctrica de estas plataformas así como un análisis térmico del conjunto de toda la misión. L'UPC NanoSat Lab és un laboratori de la Universitat Politècnica de Catalunya, focalitzat en el disseny i desenvolupament de nano i picosatèl·lits. Aquest tipus de plataformes tenen limitacions significatives en dimensions i potència. Tanmateix, degut al seu reduït cost, existeix un impuls creixent per part de moltes empreses i universitats que estan invertint els seus recursos en aplicacions innovadores d'observació terrestre i comunicacions. Aquesta treball de fi de grau forma part d'un projecte de l'UPC NanoSat Lab per l'IEEE Geoscience and Remote Sensing Society titulat "Open PocketQube Kit". Aquest projecte té com a objectiu desenvolupar diferents PocketQubes educatius, un tipus de picosatèl·lits, amb forma de cub de 5 cm de mida, que aniran integrats dins de la missió del 3Cat-8. Precisament, aquest treball de fi de grau està centrat en el disseny i implementació del subsistema d'al·limentació elèctrica d'aquestes plataformes així com un anàlisi tèrmic pel conjunt de tota la missió.

With the entry barrier for conventional small satellites continuously increasing for uni- versities and researches, this thesis means to promote a more accessible option in the form of a single unit picosatellite (1P). In this report, the design, implementation and testing procedures, alongside with the general mode of operation of these otherwise called PocketQubes will be presented. Three different configurations will be defined by means of three payloads: a VGA camera and two RFI Monitoring Receivers, at L-band and K-band. The avionics, constituting of an EPS, OBC, COMMS and an ADCS will remain mostly unchanged between the three variants. An IEEE GRSS initiative, the project has taken place, from designing to implementation and testing, within UPC?s NanoSat Lab, and is scheduled to be delivered in the shape of a kit, containing the Flight Models fully equipped with a set of manuals and tutorials for assembly, testing and operation, at the end of 2022. Additionally, a flight opportunity is envisioned for two of these PocketQubes aboard the NanoSat Lab?s future 3Cat-8 mission. Con la barrera de entrada de los pequeños satélites convencionales en continuo aumento para las universidades e investigadores, esta tesis pretende promover una opción más accesible en forma de un picosatélite de una sola unidad (1P). En este informe, el diseño, la implementación y los procedimientos de prueba, junto con el modo general de funcionamiento de estos, también llamados PocketQubes, serán presentados. Se definirán tres configuraciones diferentes mediante tres cargas útiles: una cámara VGA y dos receptores de monitorización RFI, uno en banda L y otro en banda K. La aviónica, constituida por los subsistemas EPS, OBC, COMMS y ADCS, permanecer a prácticamente sin cambios entre las tres variantes. El proyecto, una iniciativa del GRSS del IEEE, se ha llevado a cabo desde el diseño hasta la implementación y las pruebas en el NanoSat Lab de la UPC, y está previsto que se entregue en forma de kit, conformado por los modelos de vuelo Amb la barrera d’entrada als petits satèl·lits convencionals en augment continu per a les universitats i investigadors, aquesta tesi tracta de facilitar l’accés a una opció més assequible, en forma d’un picosatèl·lit d’1P. En aquest treball es presenten els procediments de disseny, implementació i proves realitzades, conjuntament amb els modes generals de funcionament d’aquests satèl·lits, anomenats PocketQubes. Es definiran tres configuracions diferents, segons la carrega útil a bord: una càmera VGA i dos sensors de RFI, un en banda L i l’altre en banda K. L’aviònica, constituïda per una EPS, una OBC, un sistema COMMS i el mòdul ADCS, romandrà pràcticament sense alteracions entre els tres models. Aquest projecte és una iniciativa del GRSS de l’IEE, i s’ha executat, des del disseny fins a la implementació i verificació, a les instal·lacions del NanoSat Lab de la UPC, i està pendent de ser entregat com a kit complet, incloent-hi els models de vol i el conjunt de manuals i tutorials de muntatge, proves i la operació, a finals de 2022. A més, es preveu una oportunitat de vol per a dos d’aquests PocketQubes a bord de la futura missió 3Cat-8 del NanoSat Lab.

Satellite simulators, such as STK, implement accurate models of the spacecrafts astrodynamics, which is crucial for some analyses. However, these simulators are insufficient simulating the networking aspects of satellites. For that reason the Distributed Satellite Systems (DSS) simulator has been implemented. The DSS is based on Network Simulator-3 (NS-3),and it is used to simulate communications of spacecrafts and constellations. The simulator allows to obtain metrics of contacts between the ground station and the satellite, and also of communications between satellites. I Distributed Satellite Systems (DSS), composed of multiple spacecraft units orbiting around the Earth, are becoming increasingly popular due to their ability to satisfy short revisit times and responsiveness. Furthermore, these DSS may be equipped with inter satellite communications and networking capabilities. Simulation techniques and computational support are required to develop and optimize such satellite structures. As a result, the major goal of the "DSS-Sim" (Distributed Satellite Systems Simulator), a project currently under development at the UPC NanoSat Lab, is to replicate all parts of this type of in-orbit architecture and analyse a variety of system-level properties. In this regard, this thesis describes the design and implementation in the DSS-Sim of two additional MAC protocols: an Aloha and a CSMA/CA MAC protocol. This thesis presents the design and implementation of the MAC protocols mentioned above, and a test section that describes the validation procedures for these protocols implemented on the DSS-Sim. Los Sistemas de Satélites Distribuidos (DSS), están compuestos por múltiples unidades de satélites que orbitan alrededor de la Tierra. Estos DSS se están volviendo cada vez más populares debido a su capacidad para satisfacer tiempos de revisita cortos y su capacidad de respuesta. Además, estos DSS pueden estar equipados con comunicaciones internas por satélite y disponer de sistemas con capacidades de red. Sin embargo, se requieren técnicas de simulación y soporte computacional para desarrollar y optimizar dichas estructuras de satélites. Por ello, el gran objetivo del "DSS-Sim" (del inglés ‘Distributed Satellite Systems Simulator’), proyecto actualmente en desarrollo en el NanoSat Lab de la UPC, es replicar todas las partes de este tipo de arquitectura en órbita y analizar una variedad de propiedades a nivel del sistema. En este sentido, esta tesis describe el diseño e implementación en el DSS-Sim de dos protocolos MAC adicionales: el Aloha y un protocolo MAC CSMA/CA. Esta tesis presenta el diseño e implementación de los protocolos MAC mencionados anteriormente, y una sección de pruebas que describe los procedimientos de validación para estos protocolos implementados en el DSS-Sim. Els Sistemes de Satèl·lits Distribuïts (DSS), estan formats per múltiples satèl·lits que orbiten al voltant de la Terra. Aquests DSS s’estan tornant cada cop més populars a causa de la seva capacitat per satisfer temps de revisita curts i la seva gran capacitat de resposta. A més, aquests DSS poden estar equipats amb comunicacions per satèl·lit internes i sistemes amb capacitats de xarxa. Tanmateix es requereixen tècniques de simulació i suport computacional per desenvolupar i optimitzar aquestes estructures de satèl·lits. Com a resultat, el principal objectiu del ‘DSS-Sim’ (de l’anglès ‘Distributed Satellite Systems Simulator’), un projecte que actualment està en desenvolupament al NanoSat Lab de la UPC, és replicar les parts d’aquest tipus d’arquitectura en òrbita i analitzar una varietat de propietats a nivell del sistema. En aquest sentit, aquesta tesi descriu el disseny i la implementació en el DSS-Sim de dos protocols MAC addicionals: l’Aloha i un protocol MAC CSMA/CA. Aquesta tesi presenta el disseny i implementació dels protocols MAC esmentats anteriorment, i una secció de proves que descriu els procediments de validació d’aquests protocols implementats al DSS-Sim.

Earth Observation applications are demanding higher spatial resolution and shorter revisit times than existing systems, which can be met by ad-hoc constellations of Federated Satellite Systems. These systems are distributed satellite architectures 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 federation concept to a multi-hop scenario, without predefining a particular satellite system architecture, and deploying temporal satellite networks. The basis of both concepts is the offer of unused satellite resources as services. Therefore, it is necessary that satellites notify their availability to the other satellites that compose the system. This work presents a novel Opportunistic Service Availability 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. The protocol has been verified in a realistic scenario composed of Earth Observation satellites, and the Telesat mega-constellation as network backbone. The achieved results demonstrate the benefits of using a protocol as the proposed one, which in some cases even doubles the amount of data that can be downloaded. To the best of our knowledge, this proposal is the first protocol that allows deploying opportunistic services for Federated Satellite Systems., 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.

Having a quality connectivity service is key in the economic, educational and health development of today’s society. However, current communication systems are not capable of providing full community connectivity, leaving the most remote areas underserved. This project analyzes how the Telesat satellite operator, through its Telesat Lightspeed constellation, proposes a business model based on deploying 298 satellites in low Earth orbits (LEO) to face the most demanding telecommunications challenges, and close the digital divide between urban and rural communities by delivering a universal, fast and affordable internet service. Therefore, studying the benefits and applications of low Earth orbits, analyzing the characteristics of Telesat and its constellation of satellites, as well as examining how it intends to carry out its value proposition and the risks it faces, are the main points on which this thesis is based.

This project aims to study the quality of communication using nanosatellites in LEO orbits. The objective is to study the signal attenuation by radio frequency (RF) antennas between a nanosatellite and a ground station, or another nanosatellite. For this purpose, a MATLAB simulator is developed that allows the modeling of satellite orbits by using TLEs, orbital elements or Walker constellations. As for the communication parameters, different transmission frequencies and atmospheric propagation models can be used. As for the antennas, two different types are used: parabolic reflectors for ground stations and patch antennas for satellites. The quality of a communication link is determined by two different methods: using the received power or the signal-to-noise ratio in reception. In the case of received power, this should be higher than the sensitivity of the transceiver under study, while signal-to-noise takes into account different digital modulations that determine the probability of message loss. Thanks to this simulator, it is possible to obtain results that determine the visibility times between satellites and/or ground stations, and to determine if the communication for a given link meets the minimum communication requirements, as well as to calculate the transmission power necessary to meet these requirements. It also performs a 3D representation in which the orbits of the satellites as well as the ground stations can be observed.

The Global Satellite Tracking Initiative aims to support international students and young professionals to set up ground stations to download real-time data and images from satellites orbiting above their regions. The objective is to empower and build capabilities among space enthusiasts around the world and to promote the space sector through hands-on activities and real space technologies related to satellite communications. The Space Generation Advisory Council, together with SatNOGS as an integral part of the Libre Space Foundation, have been supporting the initiative to enhance the development of a global open source network of satellite ground stations. The initiative will be providing all the resources, hardware, and know-how that is needed to set up ground stations. A competition was launched by the end of 2021 to select teams of space enthusiasts and supply them with a kit and step-by-step instructions on how to build their own ground stations. By setting up ground stations in backyards, local universities, or maker clubs, teams are not only self-learning about telecommunications and satellite technologies, but they are creating a meaningful impact in their local communities by bringing the broad society closer to science, technology, engineering, mathematics and, in particular, space. The initiative also intends to support space missions while engaging local communities from different regions around the world in the space sector through appealing imagery and tools. After closing the Call for Applications in this pilot initiative, 10 winning teams were selected upon receiving almost 200 applications from more than 60 countries. The selected winners are based in the following emerging space faring nations: Benin, Bolivia, Egypt, Ethiopia, Nepal, Peru, Philippines, Rwanda, Vietnam, and Zimbabwe. They are being supplied with a basic Ground Station Kit and instructions on how to receive live images and data from different space missions, starting with the following frequency bands: - 137 megahertz: To receive images from National Oceanic & Atmospheric Administration satellites. - 144-146 megahertz: To receive images and data from the International Space Station. - 440 megahertz: To receive data from numerous scientific and educational small satellites. Those teams that manage to set up the basic ground station kits and conduct some outreach and educational activities will receive a more advanced system. This paper captures the process to be followed by the selected teams, from the unboxing of the hardware to the reception and processing of data from operational space missions.

The ESA ESEO Mission [1] included an amateur radio payload [2]. The results of which included the development of radio technologies that utilised final year student projects over a 5 year period. Many lessons regarding compliance and process enabled a new payload to follow: the Student Ranging Transponder Radio for X-band and L-band (or STAR-XL). The STAR-XL design leverages key aspects of the ESEO payload design for a generic CubeSat platform; including TT&C voltage and current sense circuitry, receiver circuitry, and flight software. But instead of a maximum 4800 bps telemetry and transponder system - the STAR- XL targets a 100 kHz bandwidth system that will allow faster downlink rates that are forward error correction, link margin and modulation order dependent. With 100 kHz bandwidth, the linear receiver is designed to also operate as a transponder - enabling ranging and navigation applications such as orbit determination and further experiments from amateur radio groundstations. This paper details the recent student project efforts in three key areas: a new STM32-based on-board computer, an X-band up-converter board and dual X/L band patch (as shown in Fig. 1). The new OBC includes an IQ modulator for transmitting complex waveforms and an optimised flight software suite that takes advantage of dual DMA hardware on-chip to reduce overheads. The X-band upconverter board required the development of new safety interlock and RF chain circuitry on a Rogers (RO4350B) PCB material. A new dual X/L-band patch antenna and filter circuit is also built and measured. Each of these projects has led to new lessons and increased the real-world case studies used to teach spacecraft avionics.

Communication links over satellites allow interconnecting very distant regions to provide service where the terrestrial networks are limited. In this scenario, it is of major importance to devise mechanisms accounting for the improved freshness of packets given the impact of large distances. Their analysis is particularly important when considering the deployment of sensors in remote areas, where satellite links may introduce a high delay in the communication system. In this respect, we report the use of age of information (AoI) metrics to evaluate users' allocation mechanisms. We use power-domain non-orthogonal multiple access (NOMA) as an alternative to orthogonal multiple access (OMA) to optimally reduce the age of received packets. We derive the proper formulation to account for a fairness condition when pairing users accounting for both; the user's needs to transmit information and the allowable link rate. Comparative results are provided by numerically evaluating the solution for NOMA and OMA accounting for the peak age of information (PAoI) metric. We show that the resource allocation mechanisms in NOMA results in less PAoI (40%) compared to OMA. We remark this result through extensive numerical simulations based on actual uplink satellite communication links accounting for 500 users. This work has been supported by the Spanish National Project IRENE (PID2020-115323RB-C31, PID2020- 115323RB-C33 / AEI / 10.13039/501100011033).

Next-generation satellite systems require more flexibility in resource management such that available radio resources can be dynamically allocated to meet time-varying and non-uniform traffic demands. Considering potential benefits of beam hopping (BH) and non-orthogonal multiple access (NOMA), we exploit the time-domain flexibility in multi-beam satellite systems by optimizing BH design, and enhance the power-domain flexibility via NOMA. In this paper, we investigate the synergy and mutual influence of beam hopping and NOMA. We jointly optimize power allocation, beam scheduling, and terminal-timeslot assignment to minimize the gap between requested traffic demand and offered capacity. In the solution development, we formally prove the NP-hardness of the optimization problem. Next, we develop a bounding scheme to tightly gauge the global optimum and propose a suboptimal algorithm to enable efficient resource assignment. Numerical results demonstrate the benefits of combining NOMA and BH, and validate the superiority of the proposed BH-NOMA schemes over benchmarks. This work was supported in part by the Luxembourg National Research Fund (FNR) CORE projects ROSETTA (under grant C17/IS/11632107) and FlexSAT (under grant C19/IS/13696663).

Zero-Forcing (ZF) and Regularized Zero-Forcing (RZF) precoding are low-complexity sub-optimal solutions widely accepted in the satellite communications community to mitigate the resulting co-channel interference caused by aggressive frequency reuse. However, both are sensitive to the conditioning of the channel matrix, which can greatly reduce the achievable gains. This paper brings the attention to the benefits of a design that allows some residual received interference power at the co-channel users. The motivation behind this approach is to relax the dependence on the matrix inversion procedure involved in conventional precoding schemes. In particular, the proposed scheme aims to be less sensitive to the user scheduling, which is one of the key limiting factors for the practical implementation of precoding. Furthermore, the proposed technique can also cope with more users than satellite beams. In fact, the proposed precoder can be tuned to control the interference towards the co-channel beams, which is a desirable feature that is not met by the existing RZF solutions. The design is formulated as a non-convex optimization and we study various algorithms in order to obtain a practical solution. Supporting results based on numerical simulations show that the proposed precoding implementations are able to outperform the conventional ZF and RZF schemes. This work has been partially supported by the Luxembourg National Research Fund (FNR) under the project FlexSAT (C19/IS/13696663) and by the ministry of Science, Innovation and Universities, Spain, under project TERESA-TEC2017-90093- C3-1-R (AEI/FEDER, UE).

The space market is experiencing a tremendous transformation with private companies taking the lead and launching an increasing number of satellites. Up until recently, geostationary orbits were the most used for commercial exploitation, however, in recent years Low and Very Low Earth Orbits have been playing a very important role in the evolution of the space market. While the Earth Observation industry has continued developing, the last couple of years have seen the focus shifting towards telecommunications. As part of the Discoverer project, which is developing terrestrial observation satellites for Very Low Earth Orbits, this study aims to look beyond observation satellites to propose a market for satellites in the Internet of Tomorrow technologies. During the course of this project the American company Starlink has been gaining traction in their goal to create a constellation of satellites in Low and Very Low Earth Orbits to provide internet in all remote parts of the planet, A business plan has been made in which Discoverer could develop satellites for low and very low orbits with a focus on telecommunications use. As part of the study, business opportunities have been proposed and, above all, the greatest emerging competitor, Starlink, has been analyzed.

This paper proposes a hybrid network architecture combining a cell-free Massive MIMO terrestrial layout with a low Earth orbit satellite segment jointly targeting the maximization of the minimum per-user rate in the coverage area. Towards this end, an optimization framework is proposed, alongside a greedy solution, that diverts the terrestrial users experiencing poor propagation conditions to the satellite segment. Simulation results show the substantial benefits this integrated approach brings along, very specially when the terrestrial segment operates single-antenna access points or is sparsely deployed., Grant numbers : TERESA - Hybrid TERrEstrial/Satellite Air Interface for 5G and Beyond (TEC2017-90093-C3-1-R).

During the last years, satellite systems have evolved from monolithic spacecraft to distributed architectures. These new architectures are based on a group of satellites that works to achieve a common goal or mission. Among the different distributed architectures, the Federated Satellite System concept is the more promising one for Earth Observation. This novel concept aims at establishing win-win collaborations between the satellites to share unallocated resources, such storage capacity or downlink opportunities. The deployment of this concept requires the development of new technologies and the necessary equipment to perform it. In particular, a simulation engine that represents the interaction between the satellites becomes a crucial facility. Among the different simulation engines, no one is able to integrate satellite dynamics and communications interaction. These two features are essential to correctly represent the interaction of the satellites in a federation. For this reason, a dedicated simulator was developed by the NanoSat Lab research group in UPC. This engine provides a simulation framework in which satellites can be defined with different modules that represents the satellite resources, and the corresponding protocols to interact between them. The simulator remains still under development, and new features must still be implemented. Among the different ones, the development of a viewer that is able to represent the status of the interactions in the satellite trajectory becomes an interesting feature to understand the nature of federations. This dissertation addresses this new feature, implementing a dedicated viewer using current technologies. The development has addressed the different challenges associated to integrating a new viewer in the simulator, and in the standard visualization tool. The resulting implementation is able to represent the satellite interaction using a temperature representation in which more transmission heat the communication link. This resulting viewer will contribute in the future research associated to the Federated Satellite Systems. En els últims anys, els sistemes de satèl·lits han evolucionat, passant de ser naus monolítiques a tractar-se d'arquitectures distribuïdes. Aquestes noves arquitectures es basen en grups de satèl·lits que treballen en poder assolir un objectiu o missió comuna. Entre els diferents tipus d'arquitectures distribuïdes, el concepte de les Federated Satellite System és el més prometedor de cara a l'Observació terrestre. Aquest concepte innovador mira d'establir col·laboracions win-win entre els satèl·lits i compartir d'aquesta manera recursos que no es troben en ús, tals com l'emmagatzematge o l'opció de Downlink. El desplegament d'aquest concepte requereix el desenvolupament de noves tecnologies i d'un equipament necessari per a realitzar-ho. En particular, un simulador que representi la interacció entre satèl·lits esdevé un bé fonamental. Entre els diferents sistemes de simulació, cap és capaç d'integrar dinàmiques dels satèl·lits i comunicacions. Aquestes dos característiques són essencials per a representar correctament la interacció entre satèl·lits en una FSS. Per aquest motiu, un simulador dedicat estava sent desenvolupat pel grup de recerca del NanoSat Lab de la UPC. Aquest motor proporciona un entorn de simulació en el qual els satèl·lits poden ser definits amb diferents mòduls que representin els seus recursos, i els corresponents protocols per a poder interactuar entre ells. El simulador és encara en fase de desenvolupament, i noves característiques necessiten ser implementades. Entre aquestes característiques, el desenvolupament d'un visor que permeti representar l'estat de les interaccions en la trajectòria d'un satèl·lit és una característica que pot ser important de cara a entendre el funcionament de les federacions de satèl·lits. Aquesta dissertació tracta aquesta nova característica, implementant un visor dedicat utilitzant tecnologies actuals. El desenvolupament enfoca diferents reptes associats a integrar una now viewer en el simulador, i en l'estàndard de visualització. La implementació resultada és capaç de representar la interacció entre satèl·lits mostrant en una escala de calor l'activitat d'un enllaç. Aquesta viewer contribuirà en el futur de la recerca associada a les Federated Satellite Systems..

Non-Orthogonal Multiple Access (NOMA) has potentials to improve the performance of multi-beam satellite systems. The performance optimization in satellite-NOMA systems can be different from that in terrestrial-NOMA systems, e.g., considering distinctive channel models, performance metrics, power constraints, and limited flexibility in resource management. In this paper, we adopt a metric, Offered Capacity to requested Traffic Ratio (OCTR), to measure the requested-offered data (or rate) mismatch in multi-beam satellite systems. In the considered system, NOMA is applied to mitigate intra-beam interference while precoding is implemented to reduce inter-beam interference. We jointly optimize power, decoding orders, and terminal-timeslot assignment to improve the max-min fairness of OCTR. The problem is inherently difficult due to the presence of combinatorial and non-convex aspects. We first fix the terminal-timeslot assignment, and develop an optimal fast-convergence algorithmic framework based on Perron-Frobenius theory (PF) for the remaining joint power-allocation and decoding-order optimization problem. Under this framework, we propose a heuristic algorithm for the original problem, which iteratively updates the terminal-timeslot assignment and improves the overall OCTR performance. Numerical results verify that max-min OCTR is a suitable metric to address the mismatch issue, and is able to improve the fairness among terminals. In average, the proposed algorithm improves the max-min OCTR by 40.2% over Orthogonal Multiple Access (OMA)., Comment: 11 pages, 5 figures

The energy allocation problem in a massive access setting under iterative successive interference cancellation (SIC) is undertaken in this work. The classic one-iteration SIC still has room for improvement when the channel coding schemes adopted are non-error free. In this work, we investigate a satellite return link in which transmitters employ the same physical layer and transmission protocol: a given encoder, and spreading-based nonorthogonal multiple access. Leveraging iterative SIC, the gateway is endowed with strong interference suppression potential to deal with many uncoordinated transmissions. We elaborate on the interplay between energy and reliability for all users by designing an energy allocation with minimum energy expenditure when the iterative SIC receiver performs two decoding attempts per user. We resort to the user-asymptotic regime to address the randomness in the multi-feature system model of two-iteration SIC, which has turned the analysis into a deterministic one. We formulate our final design as a vector optimization aided by tools from the calculus of variations. We show the competitive performance achieved by the designed allocation, specially under encoders associated with short-length codes. We also assess our analysis by simulating a low-level SIC implementation. Work supported in part by Agencia Estatal de Investigacion (AEI, Spain) and by European Regional Development Fund (ERDF) through project RODIN (PID2019-105717RB-C22), and in part by the Catalan administration (AGAUR) under Grant 2017 SGR 578 and Fellowship 2020FI B2 00062.

Secure and reliable exchange of data and information plays a crucial role in our society, for example protecting money transfers, commercial transactions, medical data, remote control of sensible infrastructures, etc. Efforts are striving towards achieving global network coverage even in remote geographical areas. In this context, the QUANGO (cubesat for QUANtum and 5G cOmmunication) project, started in January 2021 under the EU Horizon 2020 Research and Innovation program, is aimed at designing and prototyping the key elements of a satellite mission that targets the delivery of both IoT services and Quantum Key Distribution (QKD) services, implemented using a constellation of CubeSats that operate in LEO. The rationale behind this vision is to address the growing need for the safe, reliable, and ubiquitous exchange of data in our society that is becoming of paramount importance for a plethora of activities. The implementation of this project can provide a new paradigm to share the satellite infrastructure required for secure communication based on quantum technologies and for 5G communication. The spacecraft will carry two interconnected payloads: 1. A 5G IoT radio, called access network payload, based on a flexible software-defined radio (SDR). 2. A secure communication system based on a quantum link to distribute quantum keys to the ground. The combination of these two payloads allows for the implementation of a QKD service where the 5G IoT payload in addition to the delivery of IoT services, is intended to be used as an integral part of the envisioned QKD solution. Moreover, the combination of these two payloads will contribute to reduce the cost of both services by sharing the satellite platform and study how these two technologies can further improve synergically, getting benefits from each other’s ecosystem. The project is being developed by a consortium of European universities, research centres and SME with a strong heritage in areas such as quantum cryptography, optical communication, microsatellites development and 5G networks. The objective of the paper is to present an overview of the QUANGO project along with preliminary design considerations of the mission and platform to be developed. This work was supported by the QUANGO project (see https://quango.dei.unipd.it/), funded by the EU in the frame of Horizon 2020 programme. Peer Reviewed Article signat per 17 autors/es: D. Sarica (a), A. Balossino (a), S. Simonetti (a), G. Vallone (b), P. Villoresi (b), F. Berra (b), M. Guadalupi (c), J. Ferrer (c), I. Llorens (c), R. Ferrús (c), A. Francesconi (d), F. Sansone (d), E. Birello (d), V. Pruneri (e), I. H. L. Grande (e), E. Diamanti (f), M. Schiavon (f) (a) Argotec Srl, Via Cervino 52, 10155, Torino, Italy, {danilo.sarica, alessandro.balossino, simone.simonetti} @argotecgroup.com / (b) Department of Information Engineering, University of Padova, I-35131 Padova, Italy, {vallone, paolo.villoresi,} @dei.unipd.it, federico.berra@phd.unipd.it / (c) Sateliot, Rambla de Catalunya 124, 08008, Barcelona, Spain, {marco, josep.ferrer, isaac.llorens, ramon.ferrus} @sateliot.space / (d) Stellar Project, Via Niccolò Tommaseo, 69/D, 35131, Padova, Italy, {alessandro.francesconi, francesco.sansone, edoardo.birello} @stellarproject.space / (e) ICFO, Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, Barcelona, Spain, {Valerio.Pruneri, Ignacio.Lopez} @icfo.eu / (f) Sorbonne Université, 4 place Jussieu, 75005, Paris, France, {eleni.diamanti, matteo.schiavon} @lip6.fr

Low-complexity suboptimal solutions are widely accepted to design spatial precoders that mitigate the resulting co-channel interference in multibeam high throughput satellites, which is caused by the aggressive frequency reuse. The most widely accepted solution, due to its simplicity and robustness to different channel conditions, is the so-called minimum Mean Square Error (MMSE) precoder. This work reviews the different rationals that support this technique and presents an alternative that maximizes the directivity. With this new point of view we propose a solution that is suitable for both the unicast and the multicast scenario. The latter is quite unexplored in the existing literature, partly explained by its loss of performance with respect to the unicast case. The proposed technique presents a practical and more clear design than the MSE, and the numerical simulations proof its gains compared to the benchmark. © VDE VERLAG GMBH · Berlin · Offenbach., This work is supported by the Spanish ministry of science and innovation under project IRENE (PID2020-115323RB-C31 / AEI / 10.13039/501100011033) and from the Catalan Government (2017-SGR-1479). © 2021, IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other work.

Cellular networks play a very important role in nowadays paradigm which goal is to establish connectivity all around the world. Low power wide area networks (LPWAN) seem to fit well within low-cost devices, which constitute a great part of the electronics market. In this context, the narrowband internet of things (NB-IoT) protocol specified by the 3GPP is consolidating as one of the most adopted technologies in the field of LPWAN, together with LoRaWAN. With the goal of reaching global coverage, the NB-IoT protocol, which was mainly designed for terrestrial cellular networks, is now being extended to be able to work also on satellite networks. The support of satellite access is seen as the enabler of truly massive machine-type communications (mMTC) into areas that cellular connectivity is limited or inexistent (remote areas, air and sea communications). This thesis provides a performance assessment of the NB-IoT protocol under different satellite link conditions and transmission modes. The assessment is conducted using the MATLAB LTE Toolbox. Las redes móviles tienen un papel muy importante en la actualidad, puesto que tienen como objetivo establecer conectividad en todo el mundo. Las redes de bajo consumo y largo alcance (LPWAN) parecen encajar bien en un entorno donde los dispositivos de bajo coste constituyen una gran parte del mercado de la electrónica. En este contexto, el protocolo NB-IoT especificado por el 3GPP se consolida como una de las tecnologías más adoptadas en el contexto de LPWAN, junto con LoRaWAN. Con el objetivo de conseguir una cobertura global, el protocolo NB-IoT, que fue diseñado principalmente para redes de telefonía terrestre, ahora se está ampliando para poder trabajar también en redes de satélite. El acceso por satélite es visto como la puerta hacia las comunicaciones de tipos máquina masiva (mMTC) en áreas donde la conectividad celular es limitada o inexistente (áreas remotas, comunicaciones aéreas y marítimas). Esta tesis proporciona una evaluación del rendimiento del protocolo NB-IoT bajo diferentes condiciones de enlace por satélite y modos de transmisión. La evaluación se realiza utilizando la caja de herramientas MATLAB LTE. Les xarxes mòbils tenen un paper molt important en l'actualitat, ja que tenen com a objectiu establir connectivitat a tot el món. Les xarxes de baix consum i llarg abast (LPWAN) semblen encaixar bé en un entorn on els dispositius de baix cost constitueixen una gran part del mercat de l'electrònica. En aquest context, el protocol NB-IoT especificat pel 3GPP es consolida com una de les tecnologies més adoptades en el context de LPWAN, juntament amb LoRaWAN. Amb l'objectiu d'aconseguir una cobertura global, el protocol NB-IoT, que va ser dissenyat principalment per a xarxes de telefonia terrestre, ara s'està ampliant per poder treballar també en xarxes de satèl·lit. L'accés per satèl·lit és vist com la porta cap a comunicacions de tipus màquina massiva (mMTC) en àrees on la connectivitat cel·lular és limitada o inexistent (àrees remotes, comunicacions aèries i marítimes). Aquesta tesi proporciona una avaluació del rendiment del protocol NB-IoT sota diferents condicions d'enllaç per satèl·lit i modes de transmissió. L'avaluació es realitza utilitzant la caixa d'eines MATLAB LTE.

The 3rd Generation Partnership Project (3GPP), the standard development organization in charge of the 5G mobile system specifications, is currently developing the adaption of the NB-IoT protocol for non-terrestrial networks (NTN), referred to as NB-IoT NTN. The NB-IoT NTN protocol is expected to operate, among others, in LEO constellations. To that end, the NB-IoT protocol originally conceived for terrestrial access is being enhanced to address the specific characteristics of LEO satellite channels, including e.g. timing relationship enhancements in random access and scheduling processes to deal with the longer propagation delays of satellite channels and new Doppler precompensation mechanisms. Mobility management improvements to cope with moving satellite cells and noncontinuous operation of the service link are also being worked out, leading to e.g. the specification of new system information messages encoding satellite ephemerides data and specific tracking area management approaches for satellite access. The possibility to use the same protocol NB-IoT for both terrestrial and satellite access offers an unprecedented opportunity for massive IoT services, which will benefit from the global coverage provided by satellites. In this context, this paper describes the key design considerations and main system components of a NB-IoT NTN solution that is being developed for operation with CubeSat platforms in low-density LEO constellations. Results and discussion of technical challenges are provided in the areas of link budget, beam layout configurations, capacity and achievable service performance indicators.

This paper investigates a novel closed-form noniterative precoding technique for multicast multibeam satellite systems. Next-generation satellite systems will be benefited from the flexible use of the satellite resources especially its power flexible allocation among beams. Intending to obtain a low-computational complexity design, we revisit the well-known signal-to-leakage-and-noise ratio design for multicast transmission. Two alternatives are introduced considering both the physical meaning of the ratio and certain multicast channel vector mapping. We observe the benefits of these techniques in satellite flexible payloads. The proposed technique shows a substantial gain compared to the benchmark according to the numerical simulations. Intuitive insights on the precoding behaviour are also presented. This work is funded by Ministry of Science, Innovation and Universities, Spain, under project TERESA -TEC2017-90093-C3-1-R (AEI/FEDER, UE) and by Catalan government under the grant 2017-SGR-01479.

As the new space revolution is being led by several operators of large Low Earth Orbit satellite constellations, and research into satellite communications becomes more prevalent, it is increasingly necessary to make access to research in this field as open as possible. This research has been around the development of a satellite networking simulator to enable further research, specially in the satellite-based airborne communications. This simulator has been implemented as flexible as possible to enable further extending features. It ingests real-world data from ground stations, aircraft and satellites, simulates and plans discrete events, and post-processes the network metrics obtained. Several case studies are presented in this thesis for analyzing constellation deployment as well as for exploratory network analysis and validation of the simulator.

Nowadays, constellations and distributed networks of satellites are emerging as clear development trends in the space system market to enable augmentation, enhancement, and possibilities of new applications for future Earth Observation (EO) missions. While the adoption of these satellite architectures is gaining momentum for the attaining of ever more stringent application requirements and stakeholder needs, the efforts to analyze their benefits and suitability, and to assess their impact for future programmes remains as an open challenge to the EO community. In this context, this paper presents the mission and system architecture conceived during the Horizon 2020 ONION project, a European Union research activity that proposes a systematic approach to the optimization of EO space infrastructures. In particular, ONION addressed the design of complementary assets that progressively supplement current programs and took part in the exploration of needs and implementation of architectures for the Copernicus Space Component for EO. Among several use cases considered, the ONION project focused on proposing system architectures to provide improved revisit time, data latency and image resolution for a demanding application scenario of interest: Marine Weather Forecast (MWF). A set of promising system architectures has been subject of a comprehensive assessment, based on mission analysis expertise and detailed simulation for evaluating several key parameters such as revisit time and data latency of each measurement of interest, on-board memory evolution and power budget of each satellite of the constellation, ground station contacts and inter-satellite links. The architectures are built with several heterogeneous satellite nodes distributed in different orbital planes. Each platform can embark different instrument sets, which provide the required measurements for each use case. A detailed mission analysis has then been performed to the selected architecture for the MWF use case, including a refined data flow analysis to optimize system resources; a refined power budget analysis; a delta-V and a fuel budget analysis considering all the possible phases of the mission. This includes from the correction of launcher injection errors and acquisition of nominal satellite position inside the constellation, orbit maintenance to control altitude, collision avoidance to avoid collision with space debris objects and end-of-life (EOL) disposal to comply with EOL guidelines. The relevance of the system architecture selected for the MWF has been evaluated for three use cases of interest (Arctic sea-ice monitoring, maritime fishery pressure and aquaculture, agricultural hydric stress) to show the versatility and the feasibility of the chosen architecture to be adapted for other EO applications., This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 687490.

Next generation satellite payload technology is expected to provide digital processing capabilities. This will pave the way to regard satellites as flying base stations. However, the initial access procedure must be improved. In this work we focus on non-geostationary earth orbit (NGEO) satellite networks. In this scenario, the random access preamble signal and the detection must be robust to large carrier frequency offsets (CFOs). Towards this end, we investigate the adoption of the pruned discrete Fourier transform spread filter bank multicarrier waveform. The proposed design is suitable for the access scheme of forthcoming 5G-based NGEO satellite communications. The reason is twofold. First, it improves the spectral confinement with respect to the standard single-carrier frequency-division multiplexing (SC-FDM) waveform. Second, it achieves a high level of commonality with 5G new radio, by keeping unchanged the subcarrier spacing, the slot duration and the preamble sequence. Remarkably, the new design allows the straightforward application of non-coherent post detection integration (NCPDI) techniques, which divide the correlation in blocks. Numerical results show that the proposed solution reduces out-of-band emissions and the missed detection probability in presence of CFO, with respect to the conventional approach based on SC-FDM and preamble detection with full-length correlation. This work has received funding from the ministry of Science, Innovation and Universities under project TERESA-TEC2017-90093-C3-1-R (AEI/FEDER,UE) and under grant RTI2018-099841-B-I00 and from the Catalan Government (2017-SGR-1479).

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 Grant MDM-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 part by the Secretaria d’Universitats i Recerca del Departament d’Empresa i Coneixement de la Generalitat de Catalunya under Grant 2017 SGR 376.

This paper tackles the problem of user scheduling in satellite content delivery networks with precoding. The clustering process has to consider two crucial and independent characteristics of the user terminals. On the one hand, users belonging to the same group shall have a reduced Euclidean norm between their channel vectors in order to obtain the maximum precoding gain. On the other hand, with the aim of exploiting the multicast capabilities of the system, user terminals grouped in the same cluster shall have requested the same content. The resulting clustering problem is formulated as a multigraph (also known as multiview) spectral clustering problem. The paper shows that this unsupervised learning framework is able to capture the different peculiarities of the mentioned problem. Two different techniques are introduced and validated in a close-to-real numerical simulation. This work has received funding from the Spanish ministry of Science, Innovation and Universities under project TERESA-TEC2017-90093-C3-1-R (AEI/FEDER,UE), and by the Catalan Government under grant 2017-SGR01479.

The DISCOVERER project is developing technologies to enable commercially-viablesustained-operation of satellites in very low Earth orbitsfor communications and remote sensing applications. Operatingcloser to the surface of the Earthsignificantly reduceslatency for communications applications and improves link budgets, whilstremote sensing also benefitsfrom improved link budgets,the ability to havehigher resolution or smaller instruments, all of which providecost benefits. In addition, all applications benefit from increased launch mass to lower altitudes, whilst end-of-life removal is ensured due to the increased atmospheric drag. However, this drag must also be minimised and compensated for. DISCOVERER is developing several critical technologies to enable commercially-viable operations in at these lower altitudesincluding aerodynamic materials, aerodynamic attitude and orbitcontrol methods, atmosphere breathing electric propulsion and an in-situenvironment monitoring payload. Thecurrentstatus of these developments are summarised, along with the plans for thecoming year. The DISCOVERER project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 737183.

This paper investigates the application of multicast non-orthogonal multiple access (MC-NOMA) schemes to the forward link of a satellite communication system. In multicast transmission each frame contains information of multiple users. To benefit from the theory developed in NOMA, the proposed scheme creates two groups of users within each beam. The analysis conducted in this work reveals that the user grouping has an impact on the performance. In the light of this observation, power allocation and user clustering techniques have been derived to either maximize the sum-rate or achieve max-min fairness. The numerical simulation results show that MC-NOMA outperforms multicast orthogonal multiple access (MC-OMA) schemes, where different groups are served in orthogonal resources. Moreover, the gain of MC-NOMA over the MC-OMA becomes more prominent as number of users per group and the transmit power increases. The results show the minimum-rate and the sum-rate of MC-NOMA can be increased by a factor 2 and 1.45 with respect to MC-OMA, respectively.

This paper aims at designing an onboard beam generation process for a hybrid onboard on-ground multibeam satellite architecture. The proposed method offers a good tradeoff between total throughput and feeder link bandwidth requirements compared with pure on-ground systems. Full frequency reuse among beams is considered, and the beamforming at the satellite is designed for supporting interference mitigation techniques. In addition, in order to reduce the payload cost and complexity, this onboard beamforming is assumed to be constant and the same for forward and return link transmissions so that the same array-fed reflector can be used for forward and return links, leading to a substantial reduction of the payload mass. To meet all these requirements, a novel robust minimum mean square error optimization is conceived. The benefits of the considered scheme are evaluated with respect to the current approaches both analytically and numerically. Indeed, we show that with the DVB-RCS and DVB-S2 standards, our proposal allows increasing the total throughput within a range between 6% and 15% with respect to other onboard processing techniques in the return and forward link, respectively.

In the past two decades, a silent revolution has taken place in the space domain, leading to what today is known as “New Space.” We have passed from a selected group of countries, space agencies, and big industries building, launching, and operating satellites and other spacecrafts, of a scenario in which many universities and research institutes can do it. The key of this was the definition of the “CubeSat” standard, back to 1999. In 2013, it all took off on the commercial Earth Observation sector with the first launches from two companies that are now running 100+ CubeSat constellations for optical imaging or weather prediction, with very low revisit times. Today, the same revolution is taking place in the fields of Telecommunications, and Astronomical Scientific missions. In this chapter, the evolution of the space sector is briefly revised until the arrival of the CubeSats. Then, the CubeSat intrinsic limitations are discussed as they are key to understand the development and current situation of the CubeSat sector. NASA and ESA strategies are also presented. The chapter concludes with a summary of the technology roadmap to enable the next generation of CubeSat-based missions, including satellite constellations or federations, formation flying, synthetic apertures… This work has been supported by an ICREA Acadèmia award from the Generalitat de Catalunya to Prof. A. Camps. The author wants to express his gratitude to Profs. A. Golkar (Skoltech, Moscow, Russia) and H. Park (Universitat Politècnica de Catalunya, Barcelona, Spain) for the revision of this chapter and useful comments.

An optimal payload selection conducted in the frame of the H2020 ONION project (id 687490) is presented based on the ability to cover the observation needs of the Copernicus system in the time period 2020–2030. Payload selection is constrained by the variables that can be measured, the power consumption, and weight of the instrument, and the required accuracy and spatial resolution (horizontal or vertical). It involved 20 measurements with observation gaps according to the user requirements that were detected in the top 10 use cases in the scope of Copernicus space infrastructure, 9 potential applied technologies, and 39 available commercial platforms. Additional Earth Observation (EO) infrastructures are proposed to reduce measurements gaps, based on a weighting system that assigned high relevance for measurements associated to Marine for Weather Forecast over Polar Regions. This study concludes with a rank and mapping of the potential technologies and the suitable commercial platforms to cover most of the requirements of the top ten use cases, analyzing the Marine for Weather Forecast, Sea Ice Monitoring, Fishing Pressure, and Agriculture and Forestry: Hydric stress as the priority use cases.

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. A switchable multi-antenna architecture for lens-assisted beamsteering in the Ka-band region allocated for 5G communications (24-30 GHz) is proposed. The radiating elements are bow-tie antennas mounted with a 3D printed high-permittivity dielectric lens (e r = 10). A 5-element array is simulated showing switchable 30° beam steering over a 120° sector with 19 dB maximum gain. Single antenna measurements of a scaled prototype with a Polylactic Acid (PLA) lens (e r = 2.7) show gains around 11 dB, in agreement with projected performances.

This paper introduces the notion of beam-free satellite systems and it investigates different scheduling algorithms for this architecture. Attending to the current satellite gateway cloudification, this paper assumes that users from different beams can be scheduled over the same frame. Indeed, considering full frequency reuse among beams and on ground precoding, we show that whenever the scheduler is able to freely group users independently of their beam location, large attainable rates are obtained. In addition, we also consider that the gateway is able to select a number of simultaneous transmissions which leads to a substantial sum-rate increase. A scheduling scheme based on spectral clustering is proposed and it shows a higher performance compared to other state-of-the-art alternatives. In addition, our method is able to deal with different user terminal traffic classes. Based on the numerical results obtained considering a close-to-real multibeam satellite pattern, we point out that the current per-beam scheduling process is an inefficient network management for multibeam satellite systems using precoding., Grant numbers : This work has received funding from the Ministerio de Ciencia, Innovación y Universidades under project TERESA-TEC2017-90093-C3-1-R (AEI/FEDER,UE) and from the Catalan Government (2017-SGR-1479).© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. The Operational Network of Individual Observation Nodes (ONION) project evaluated the benefits of applying Distributed Satellite System (DSS) architectures to Earth Observation. One of its outcomes is the identification of Arctic services as top priority current user needs that require near-realtime observations. Using Inter-Satellite Communications (ISC) capabilities, a Federated Satellite System (FSS) can establish a win-win collaboration between two spacecrafts to provide these services. However, as a FSS is established during the contact between two satellites, the service duration is limited. Therefore, the Internet of Satellites (IoSat) paradigm promotes the use of multi-hop sporadic networks to deploy FSS. In this context, the routing protocol (which identifies routes between a source-destination pair) becomes crucial. One of the most extended networks is the Mobile Ad-hoc Network (MANET), in which nodes are constantly moving and changing the network topology. In principle, applying MANET technologies in the IoSat context would provide self-organization, self-configuration, and flexibility to satellite systems. The Optimized Link-State Routing (OLSR) protocol is the predominant solution in MANET, because it quickly reacts against topology changes. This article aims at studying the benefits of using satellite networks with MANET solutions (e.g. OLSR) for polar satellite missions. The results presented in this article demonstrate that the access time is significantly improved, and thus these new Arctic services can be achieved.

Soil moisture constitutes one of the main factors for the study where there is a water deficit in the soil, mainly for semiarid regions. The semiarid region of Brazil, which extends from the northern of the Piaui State to the north of Minas Gerais, is a region vulnerable to drought. the accuracy of soil moisture estimation is important for different studies. Thus, the aim of this work is to present the soil moisture derived from different methods: 1) Soil Moisture and Ocean Salinity (SMOS) satellite products generated at the Barcelona Expert Center (BEC) [2] and 2) System of Monitoring and Alert of Anomaly for Agriculture (SIMAGRI) model, at the semiarid region of Brazil. This region is selected because is a semiarid region recently affected by droughts and in situ measurements are available. Then it is very suitable for validation. In this paper an inter-comparison work with data recorded by that network, HR SM data from BEC and SIMAGRI model is presented. This study has been carried out from November, 2015 to June, 2016. We are going to present the statistical study, using correlation coefficient (R), Bias, and Root Mean Square Error (RMSE) as metrics. The results of this study will help to analyze environmental and economic impacts when droughts are detected in this area, which economy is mainly based on agriculture and to act for mitigating the negative consequences. Finally, it seems that the combination of satellite product and SIMAGRI model can be used as a valuable tool for monitoring and alert in case of dry and/or flooding episodes in different agricultural regions.

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. This paper proposes an architecture framework for the realization of on-demand satellite network slicing that is built on the introduction of Software Defined Networking (SDN) and Network Function Virtualization (NFV) technologies. In this way, service delivery with satellite networks is shifted from a network for connectivity model to a network for service model with a high degree of service customization and adaptability, including satellite bandwidth on-demand. Under this framework, we study the resource orchestration of satellite network services by formulating the on-demand network slicing as an optimization problem that provides flexible service chaining and provisioning taking into account diversified service requirements. The objective is to determine the optimal resource allocation for supporting a satellite network slice that minimizes resources consumption while meeting service specification requirements such as the end-to-end delay.

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. IEEE Access Best Multimedia Award 2018, pel video de 4'50'' que acompanya l'article: sobre el sistema ONION (a Distributed Satellite Systems (DSS) concept formed by a Walker-Delta constellation formed by 8 heavy nodes including a SAR-X and an optical imager, and 8 small nodes including a GNSS-R payload. ONION provides innovative solutions to complement the current and planned Copernicus offer, targeting relevant and large user communities) The space industry is currently witnessing two concurrent trends: the increased modularity and miniaturization of technologies and the deployment of constellations of distributed satellite systems. As a consequence of the first trend, the relevance of small satellites in line with the “cheaper and faster” philosophy is increasing. The second one opens up completely new horizons by enabling the design of architectures aimed at improving the performance, reliability, and efficiency of current and future space missions. The EU H2020 ONION project (“Operational Network of Individual Observation Nodes”) has leveraged on the concept of Fractionated and Federated Satellite Systems (FFSS) to develop and design innovative mission architectures resulting in a competitive advantage for European Earth Observation (EO) systems. Starting from the analysis of emerging needs in the European EO market, the solutions to meet these needs are identified and characterized by exploring FFSS. In analogy with terrestrial networks, these systems envision the distribution of satellite functionalities amongst multiple cooperating spacecrafts (nodes of a network), possibly independent, and flying on different orbits. FFSS are considered by many as the future of spacebased infrastructures, as they offer a pragmatic, progressive, and scalable approach to improve existing and future space missions. This work summarizes the main results of the ONION project and the high-level design of the Marine Weather Forecast mission for polar regions. Peer Reviewed Award-winning

Routing protocols provide basic connectivity for the Internet. Routing is the action of nodes finding paths to deliver data packets. The mobile ad hoc network (MANET) is a self-configuring network, based on mobile nodes and wireless transmission. The nodes’ flexible position enables MANET’s application in various scenarios including satellite communication. While providing stronger robustness, the mobility of nodes in MANET also incurs negative effects such as disrupted links and limited route lifetime. Ad hoc On-demand Distance Vector (AODV) routing is a reactive routing protocol, in which routes are searched and established on request. In this project, AODV is studied and implemented in the satellite communication. Different parameters in the protocol are studied firstly in wireless sensor networks (WSN) simulation. By comparing the characteristics of conventional WSN and satellite communication, the parameters are adjusted to conclude the best setting for this scenario. We survey the performance of AODV in satellite communication using ns-3 simulation engine. Finally, we propose four solutions to handle the possible errors in the implementations of AODV

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.

© . This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ Highlights The climatology of desert dust events over the whole European region is presented. This study is based on the data of BSC-DREAM8b model and other validation tools. AERONET and satellite data are used for validation of the model outputs. The most affected areas are the central sectors, mainly in spring and summertime. Main dust contributors, over the European region are the western and central Sahara.

We present the results of the performance evaluation of polarization-time coding and soft interference cancellation in multi-beam satellite systems a ected by co-channel interference in realistic setups. The standard of Broadband Global Area Network service (BGAN) has been considered as reference for the physical layer and realistic interference and channel models have been adopted. The work has been carried out in the framework of the Next Generation Waveform for Increased Spectral E ciency (NGWISE) project founded by the European Space Agency (ESA).

New highly efficient, reliable, and low complexity Random Access Schemes are under research especially under the Machine to machine (M2M) communications paradigm. One of the main challenges is the inter-user interference, which constitutes the limiting factor to network performance, especially when dense wireless systems sustaining high traffic loads are deployed. Successive Interference cancellation (SIC) policies have proved an invaluable tool in order to counteract this problem. Nonetheless, the success of such IC schemes depends heavily on the received power distribution. For this reason, the aim of the project is to evaluate the performance of novel Successive Interference Cancellation schemes in real practical scenarios, in particular a land mobile satellite channel. First, we will design a simulator that will provide real profiles of received power distribution for a land mobile satellite channel. We will consider a massive user spread-spectrum Multiple Access (MA) network for wide area Machine to Machine (M2M) communications. Second, we will make use of Variational Calculus (VC) and novel Successive Interference Cancellation Techniques and with the help of Monte Carlo and Differential Equations computations, we will evaluate the performance in real practical scenarios when user transmissions are subject to an average energy constraint and users share the same Forward Error Correction (FEC) code and modulation scheme. Actualmente se está investigando nuevos esquemas de acceso aleatorio altamente eficientes, confiables y de baja complejidad, especialmente bajo el paradigma de comunicaciones máquina a máquina (M2M). Uno de los principales desafíos es la interferencia entre usuarios, que es el factor limitante para el rendimiento de la red, especialmente cuando se implementan sistemas inalámbricos densos que soportan grandes cargas de tráfico. Las políticas de cancelación de interferencias sucesivas (SIC) han demostrado ser una herramienta imprescindible para contrarrestar este problema. No obstante, el éxito de tales esquemas IC depende de la distribución de potencia recibida. Por esta razón, el objetivo del proyecto es evaluar el rendimiento de los nuevos esquemas de Cancelación sucesiva de interferencias en escenarios prácticos reales, en particular, en el canal satelital móvil terrestre. Primero, diseñaremos un simulador que proporcione perfiles reales de distribución de potencia recibida para un canal satelital móvil terrestre. Consideraremos una red con usuarios masivos de amplio espectro y de Acceso múltiple (MA) para comunicaciones de máquina a máquina (M2M) para área amplia. En segundo lugar, haremos uso de Cálculo Variacional (VC) y nuevas Técnicas de Cancelación Sucesivas de Interferencia y con la ayuda de computaciones de Monte Carlo y Ecuaciones Diferenciales, evaluaremos el desempeño en escenarios prácticos reales cuando las transmisiones de los usuarios están sujetas a una restricción de energía promedio y los usuarios comparten el mismo Código de corrección de errores (FEC) y esquema de modulación. Actualment s'està investigant nous esquemes d'accés aleatori altament eficients, fiables i de baixa complexitat, especialment sota el paradigma de comunicacions màquina a màquina (M2M). Un dels principals desafiaments és la interferència entre usuaris, que és el factor limitant per al rendiment de la xarxa, especialment quan s'implementen sistemes sense fil densos que suporten grans càrregues de trànsit. Les polítiques de cancel·lació d'interferències successives (SIC) han demostrat ser una eina imprescindible per contrarestar aquest problema. No obstant això, l'èxit de tals esquemes IC depèn de la distribució de potència rebuda. Per aquesta raó, l'objectiu del projecte és avaluar el rendiment dels nous esquemes de Cancel·lació successiva d'interferències en escenaris pràctics reals, en particular, al canal satelital mòbil terrestre. Primer, dissenyarem un simulador que proporcioni perfils reals de distribució de potencia rebuda per a un canal satelital mòbil terrestre. Considerarem una xarxa amb usuaris massius d'ampli espectre i d'Accés múltiple (MA) per a comunicacions de màquina a màquina (M2M) per un àrea extensa. En segon lloc, farem ús de Càlcul Variacional (VC) i noves Tècniques de Cancel·lació Successives d'Interferència i amb l'ajuda de computacions de Monte Carlo i Equacions Diferencials, avaluarem l'acompliment en escenaris pràctics reals quan les transmissions dels usuaris estan subjectes a una restricció d'energia mitjana i els usuaris comparteixen el mateix Codi de correcció d'errors (FEC) i esquema de modulació.

The use of dual polarization in mobile satellite systems is very promising for increasing the channel capacity. Polarized Modulation is proposed in this paper for use in practical systems, by providing simple equations for computing its capacity and featuring a link adaptation algorithm. This scheme shows remarkable gains in the spectral efficiency when compared with single polarization and other multi-antenna techniques such as V-BLAST. Polarized Modulation is a particular instance of more general Index Modulations, which are being considered for 5G networks. Thus, the proposed link adaptation algorithm could find synergies with current activities for future terrestrial networks.