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Band selection is a key strategy to address the challenges of managing large hyperspectral datasets and reduce the dimensionality problem associated with the simultaneous analysis of hundreds of spectral bands. However, the computational complexity of traditional methods makes the algorithms difficult to be deployed on board satellites. This is especially true for Small Satellites with limited computational and power resources. Moreover, existing band selection techniques often require the hypercube to be processed at least at Level-1B product, i.e., the bands need to be finely aligned before selecting them, demanding more computational resources for the on-board computer. This study presents a novel neural network-based approach for on-board band selection using data with coarse band-to-band aligned. This methodology not only simplifies the pre-processing requirements, but also opens new possibilities for efficient hyperspectral imaging from space on-board Small Satellites, such as classification, change and target detection., This project was part of the project "GENESIS: GNSS Environmental and Societal Missions – Subproject UPC", Grant PID2021-126436OB-C21 funded by the Ministerio de Ciencia e Investigación (MCIN)/Agencia Estatal de Investigación (AEI)/10.13039/501100011033 and EU FEDER “Una manera de hacer Europa”, and by a FPU fellowship from the Spanish Ministry of Education. Part of this work has also been possible thanks to the Italian Space Agency (ASI) that granted access to its PRISMA database (http://prisma.asi.it/)., Peer Reviewed, Postprint (published version)

In the context of the 3Cat-8 mission, a CubeSat standard nanosatellite under development at the NanoSat Lab (UPC), the conception, design, and measurement of a prototype have been carried out. This prototype includes one of the essential elements for communications: the antennas. Designed to be placed on one of the external faces of the spacecraft, this structure aims to group the resonant elements for the L1 band for GNSS-Reflectometry, as well as the S-band for data uplink and downlink, and the X-band for data downlink. The technology used to implement these components has been microstrip antennas due to their compact and lightweight nature. However, the proper development has been affected by external limitations, ultimately leading to the exclusion of the S-band in the measured prototype, which has been replaced by COTS antennas., En el contexto de la misión 3Cat-8, un nanosatélite del estándar CubeSat en desarrollo en el NanoSat Lab (UPC), se ha llevado a cabo la concepción, diseño y medición de un prototipo que incluye uno de los elementos imprescindibles para las comunicaciones: las antenas. Esta estructura, diseñada para ser colocada en una de las caras externas del satélite, tiene como objetivo agrupar los elementos resonantes de la banda L1 para Reflectometría GNSS, banda S para la subida y bajada de datos, y banda X para la bajada de datos. La tecnología utilizada para implementar estos componentes ha sido la de antenas microstrip, debido a su naturaleza compacta y ligera. Sin embargo, el correcto desarrollo se ha visto afectado por limitaciones externas, provocando finalmente la exclusión de los modelos de banda S en el prototipo mesurado, y su reemplazo por antenas COTS., En el context de la missió 3Cat-8, un nanosatèl·lit de l'estàndard CubeSat en desenvolupament al NanoSat Lab (UPC), s'ha dut a terme la concepció, disseny i mesura d'un prototip que inclou un dels elements imprescindibles per a les comunicacions: les antenes. Aquesta estructura, dissenyada per ser col·locada en una de les cares externes del satèl·lit, pretén agrupar els elements ressonants de la banda L1 per a Reflectometria GNSS, banda S per a la pujada i baixada de dades, i banda X per a la baixada de dades. La tecnologia utilitzada per implementar aquests components ha estat la d'antenes microstrip, gràcies a la seva naturalesa compacta i lleugera. Tanmateix, el correcte desenvolupament s'ha vist afectat per limitacions externes, provocant finalment l'exclusió dels models de banda S en el prototip mesurat, els quals han estat substituïts per antenes COTS.

3GPP, the organization developing standards for cellular technologies, is currently working on the adaptation of the NB-IoT protocol for use over Non-Terrestrial Networks (NTN). This TFG is aimed to study the performance of the protocol under different service deployment scenarios., 3GPP, la organización que desarrolla estándares para tecnologías celulares, está trabajando actualmente en la adaptación del protocolo NB-IoT para su uso en redes no terrestres (NTN). Este TFG tiene como objetivo estudiar el rendimiento del protocolo bajo diferentes escenarios de despliegue de servicios., 3GPP, l'organització que desenvolupa estàndards per a tecnologies cel·lulars, està treballant actualment en l'adaptació del protocol NB-IoT per al seu ús en xarxes no terrestres (NTN). Aquest TFG té com a objectiu estudiar el rendiment del protocol sota diferents escenaris de despliegue de serveis.

Satellite communications are of great importance in providing, for example, access to the Internet for a large part of the population. These communications are based on radio frequency links. In recent years, however, given the saturation in the radio frequency spectrum, and with the search for improvements in communication, communication through optical links emerged. Given this, this work proposes a study of radio frequency communications and optical communications, through the constellation of satellites in orbit MEO called O3b MEO. To do this, the Silleo simulator is used, a tool that allows the design of air and sea navigation support systems and orbital designs for satellite communications. This present study expands the functionality of this simulator, adding the necessary equations for the calculation and study of optical communications to perform the practical study.

This work will try to give an overview of the origin of the most impacting effects that cause disturbances in space systems. Both, the nature of the effect on the system and the design methodologies commonly used to protect against them. Throughout the work, comments will be provided which allow for a fairly complete visualization of the changing scenario and context that the sector is currently experiencing. The approach will focus on technical topics and challenges.

3Cat-8 is a mission based on a 6U satellite developed by the UPC NanosatLab group (technical University of Catalonia). The main goal of the satellite is for academic purposes and for ionospheric research. The satellite is composed in different subsystems. This Final degree thesis is focused on the communication subsystem, designing and implementing the S-band and X-band communication system., 3Cat-8 es una misión basada en un satélite 6U, desarrollado por el NanosatLab de la UPC (Universidad politécnica de Cataluña) Los Principales objetivos de este satélite son académicos para investigar sobre la Ionosfera. El satélite está dividido en diferentes subsistemas, este TFG está enfocado a la parte de Comunicaciones, más concretamente, al diseño e implementación del sistema de comunicaciones de banda X y banda S., 3Cat-8 és una missió basada en un satèl·lit 6U, desenvolupada pel NanosatLab de l'UPC (Universitat Politècnica de Catalunya) Els principals objectius d'aquest satèl·lit són, en primer lloc, acadèmics i, per altra banda, de recerca sobre la Ionosfera. El satèl·lit està dividit en diferents subsistemes. Aquest Treball de Final de Grau està enfocat a la part de comunicacions, més concretament en la part del disseny i implementació del sistema de comunicacions de banda X i banda S.

Synchronizing the local oscillators in multibeam satellites with the objective of coherent communications is still an open challenge. It has to be addressed to implement full-frequency reuse approaches, such as precoding techniques using the already deployed multibeam satellites. This article addresses the required phase synchronization to enable precoding techniques in multibeam satellite systems. It contains the detailed design of a frequency and phase compensation loop based on the proportional-integral controller, which deals with the phase drift introduced by the hardware components. Specifically, the phase noise of the local oscillators used for up and down conversion at each system element (gateway, satellite, and user terminals). The implementation of the two-state phase noise model used to emulate this phase drift is included in the article. Besides, a comparative analysis of several methods to combine the frequency and phase measurements obtained from the user terminals is also included. Finally, the performance of the proposed closed-loop synchronization method is validated through simulations using our in-house developed MIMO end-to-end satellite emulator based on SDR platforms., This research was funded by the Luxembourg National Research Fund (FNR) under the CORE project COHESAT: Cognitive Cohesive Networks of Distributed Units for Active and Passive Space Applications, grant reference [FNR11689919] and the project DISBuS: Dynamic Beam Forming and In-band Signalling for Next Generation Satellite Systems, grant reference [FNR13778945]. For the purpose of open access, the author has applied a Creative Commons Attribution 4.0 International (CCBY4.0) license to any Author Accepted Manuscript version arising from this submission. Additionally, this work has been supported by the European Space Agency under project number 4000122451/18/NL/NR ”Live Satellite Precoding Demonstration - CCN: MEO case (LiveSatPreDem).”, Peer Reviewed, Postprint (published version)

En un mundo cada vez más globalizado y en el que el tiempo es oro, se genera la necesidad de estar conectados a todo y con todos. El Internet de las Cosas (IoT) es una tendencia tecnológica revolucionaria que está transformando la forma en que interactuamos con el mundo que nos rodea. Por esta razón en este proyecto se propuso la idea de conocer más sobre este tipo de tecnología y comprobar cuan eficaz puede llegar a ser. Por lo tanto, emplearemos el uso de un módem que nos permitirá conectarnos a un conjunto de satélites que se mueven constantemente alrededor de la Tierra y, cuyo movimiento podemos predecir en función de la ubicación en la que nos encontremos. El objetivo principal es comprobar la eficacia de las transmisiones de datos a través del módem además de la ayuda del entorno LabVIEW que nos servirá para automatizar y agilizar más el proceso. La primera fase constará de una toma de contacto inicial donde hablaremos de las características del módem y las funciones que nos ofrece tanto éste como el portal o página web que nos recopila las transmisiones que han llegado con éxito. Realizaremos unas pruebas utilizando la función de la predicción del satélite a través de las coordenadas que nosotros indiquemos y plantearemos la hipótesis sobre si realmente necesitamos automatizar el proceso a través de una aplicación. Una vez planteada la hipótesis, hay que tener en cuenta que este módem ofrece una serie de comandos de programación que tienen distintas funciones, sin embargo, para poder hacer uso de éstos es necesario escribirlos de forma manual a través del puerto serie. Por este motivo se explicará el diseño de las primeras aplicaciones de prueba hechas en LabVIEW que se plantearán con la intención de comparar cuántos mensajes llegan teniendo en cuenta si se envían de forma manual o de forma automática. Estas aplicaciones son capaces de ejecutar estos comandos de forma automática y recopilar los datos que se envían correctamente, mejorando así el método de tra, The Internet of Things (IoT) is a technological revolutionary tendency which is transforming the way we interact with the world that surrounds us. By this premise, the idea of this project was proposed in order to know more about this kind of technology and check how efficient it can be. With that said, we will use a modem that will allow us to communicate to a set of satellites that move constantly around the Earth with a movement which can be predicted by setting the location where we are making the transmition. The main aim is to check the efficiency of the data transmission through the modem with the help of the program LabVIEW that will serve us to automate and speed up the process. The first phase will consist of a first contact where we will explain the characteristics and the functions that offer not only the modem but also the access of the web page that compilates the transmissions that have arrived successfully. We will make some initial tests using the satellite pass prediction function through the coordinates we indicate initially and also will make an hypothesis that poses the need to automate the process through an application or not. Once we pose the hypothesis, it is essential to remark that this modem offers a series of programming commands that have different results; however, in order to be able to use them it is necessary to execute them manually through a serial port. That is why it will be explained the design of the first test applications and how they were made with the intention of comparing how many messages arrive considering whether they are sent manually or automatically. These applications can execute these commands automatically and collecting the data that is sent correctly, thus improving the transmission method, and increasing the number of messages received by the satellite. The second phase will consist of explaining the LabVIEW environment and what its function will be in this project. We will talk about the tools used within th, Assaig per demostrar la idoneïtat de l'automatització en la transmissió de dades a satèl·lits a través de la creació d'un sistema format per 3 aplicacions a l'entorn LabVIEW per a la seva posterior funció a l'hora de posar-lo en funcionament realitzant proves a temps real i descobrint quines són els factors essencials per a una millora deficiència en la comunicació i enviament de missatges.

© 2024 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 presents a novel autonomous management system for satellite-based Non-Terrestrial Networks (NTN). It addresses the challenges of managing the operations of Low Earth Orbit (LEO) constellations for the Internet of Things (IoT), emphasizing intermittent connectivity and resource constraints. This work contributes with the description of the scheduler module alongside a customized formulation of a novel multi-objective optimization problem and its associated mathematical framework. The resultant optimization algorithm is elaborated. This Constellation Management System (CMS) is validated through a real-world scenario, revealing substantial improvements of up to 40% in task assignment and throughput rates when compared to a best-effort baseline. This study underscores the CMS’s potential to enhance IoT communication with LEO constellations through resource-efficient and business-aware satellite operations scheduling., This work was supported by the Generalitat de Catalunya; the Spanish Ministry of Economic Affairs and Digital Transformation and the European Union – NextGeneration EU; the Spanish MCIN/AEI/ 10.13039/501100011033 through project PID2019-106808RA-I00; and by Departament d’Innovacio, Universitats i Empresa, Generalitat de Catalunya 2021 SGR 00330., Peer Reviewed, Postprint (published version)

La comunicació submarina pot resultar una feina complicada degut a les grans distàncies o l’elevat cost econòmic que pot suposar. No obstant, es pretén millorar la capacitat de comunicació aplicant metodologies com la comunicació acústica. També es busca millorar la capacitat de monitoratge de les dades mitjançant canals de comunicació satel·litals. Aquest projecte es divideix en dues parts degut a la gran diferenciació de les dues parts. La primera part és realitzada per Ivan Bautista Jimenez i la segona part per Pol Pérez De Gregorio Bermúdez. La primera part té com a objectiu principal general una comunicació estable i amb una gran fiabilitat entre una estació submarina i una boia de superfície. Aquesta connexió es realitzarà utilitzant dos mòdems acústics submarins, un amb la funció d’emissor i l’altre amb la funció de receptor. El dispositiu receptor tindrà també la funció d’emmagatzemar les dades rebudes. En la segona part del projecte s’integraran diferents elements per poder emmagatzemar les dades rebudes, i posteriorment realitzar una transmissió d’aquestes a satèl·lits Argos. L’objectiu d’aquesta part és assolir aquest objectiu d’enviament de manera que s’utilitzi la menor energia possible en un espai molt reduït., La comunicación submarina puede resultar un trabajo complicado debido a las grandes distancias o al elevado costo económico que puede suponer. No obstante, se pretende mejorar la capacidad de comunicación aplicando metodologías como la comunicación acústica. También se busca mejorar la capacidad de monitoreo de los datos mediante canales de comunicación satelital. Este proyecto se divide en dos partes debido a la gran diferenciación entre ambas. La primera parte es realizada por Ivan Bautista Jimenez y la segunda parte por Pol Pérez De Gregorio Bermúdez. La primera parte tiene como objetivo principal lograr una comunicación estable y altamente confiable entre una estación submarina y una boya de superficie. Esta conexión se realizará utilizando dos módems acústicos submarinos, uno con la función de emisor y el otro con la función de receptor. El dispositivo receptor también tendrá la función de almacenar los datos recibidos. En la segunda parte del proyecto se integrarán diferentes elementos para poder almacenar los datos recibidos y posteriormente realizar una transmisión de estos a los satélites Argos. El objetivo de esta parte es lograr esta transmisión utilizando la menor cantidad de energía posible en un espacio muy reducido., Underwater communication can get to be a tough thing due to the long distances or the high economic cost we face nowadays. Nevertheless, our intentions are focused on upgrading our ability to communicate by applying some methodologies such as acoustic communication. We also look for a better way of monitoring data using satellite communication channels. This project is divided in two parts due to the differentiation between both of the parts. The first part of the project has been done by Ivan Bautista Jimenez and the second part by Pol Pérez De Gregorio Bermúdez. The objective of the first part is to generate reliable and stable communication between an underwater station and a surface buoy. This connection is going to be done using two underwater acoustic modems, one with the transmitter function and the other with the receiver function. This device will also have the ability to save all data received. For the second part of the project we will integrate different elements in order to save all received data, and afterwards carry out the transmission of this data to Argos satellites. The objective for the second part of the project is to get on with the transmission using as few energy possible and the fewer space necessary.

El objetivo principal de esta tesis era desarrollar una herramienta capaz de emular con- stelaciones de satélites LEO con Mininet. Se desarrollará para evaluar el funcionamiento de diversos algoritmos de encaminamiento en este tipo de redes. El emulador funciona reproduciendo la red en instantes determinados y actualizando la Topología cada cierto tiempo. La versión final del emulador no imita la topología de la constelación tal y como es, si no que utiliza un nodo central como matriz de conmutación creando una red con topología en estrella. Se decidió por este diseño, ya que ofrece mayor flexibilidad. Desarrollar un emulador para constelaciones de satélites LEO ha sido más complicado de lo inicialmente previsto. Principalmente debido a problemas con el rendimiento del emulador y las optimizaciones que hemos tenido que implementar. Debido a esto no hemos podido lograr uno de los objetivos originales., L'objectiu principal d'aquesta tesi era desenvolupar una eina capaç d'emular constel·lacions de satèl·lits LEO amb Mininet. Per tal de provar el funcionament de diferents algoritmes d'encaminament en aquests tipus de xarxes per tal d'avaluar el seu rendiment. L'emulador funciona reproduint l'estat de la xarxa en instants determinats i actualitzant la seva topologia cada cert temps. La versió final de l'emulador no imita la topologia la constel·lació tal com és, sinó que fa servir un node central com a matriu de commutació creant una xarxa amb topologia en estrella. S'ha decidit per aquest disseny, ja que ofereix major flexibilitat. Desenvolupar un emulador per constel·lacions de satèl·lits LEO ha estat més complicat del que inicialment havíem previst. Principalment degut a problemes amb el rendiment de l'emulador i les optimitzacions que s'han hagut d'implementar. Degut això no hem pogut validar un dels objectius originals., The main objective of this thesis was to develop a tool that could emulate LEO satellite constellations networks with Mininet for testing different multipath routing algorithms in such networks and study their performance. The emulator works by reproducing the network at a given instant and updating its chang- ing topology after a certain amount of time. The final version of this tool does not mimic the constellation network ‘as-is’, instead uses a central node, used as a commutation matrix in order to create a star network for more flexibility. Developing an emulator for LEO satellite constellations has been more challenging than we initially thought, mainly due to problems we had with performance optimization. This took a toll, and one of the original objectives was not validated through implementing it due to lack of time issues.

The Satellite communications landscape has experienced drastic changes in the last few years. User behaviour is becoming increasingly difficult to characterise, and the rise of high data demand anywhere and at anytime, is at the same time providing new opportunities for the satellite communications sector, as well as new challenges. Moreover, improvement of hardware and flexibility in satellite systems are giving the tools to satellite operators to change from classic static allocations of resources, where the resources used to serve the demand where fixed, to a dynamic approach, where the system tries to accommodate resources to serve the existing demand and adapt to dynamic environments. One of the key problems in this context is how to link mobile users to satellites efficiently in time, while considering the mobility characteristics that mobile users possess. While there are numerous works that address that problem, the complexity and uncertainty added by mobile users has not been sufficiently studied. Specifically, we argue that unexpected changes of trajectory and delays on mobile users might make planned time connections between users and satellites infeasible. This is specially critical with aeronautical users, which possess fast mobility patterns and are characterised by having important delays and trajectory changes. In view of that, we propose a formulation of this problem that addresses mobile users and their characteristics in satellite constellations, and a way to solve the problem. Different simulations are then performed to assess the validity of the proposed approach, El paradigma de las comunicaciones por satélite ha experimentado cambios drásticos en los últimos años. El comportamiento de los usuarios es cada vez más difícil de caracterizar, y el aumento de la demanda de datos en cualquier lugar y en cualquier momento ofrece al mismo tiempo nuevas oportunidades para el sector de las comunicaciones por satélite, así como nuevos desafíos. Además, la mejora del hardware y la flexibilidad en los sistemas satelitales están brindando las herramientas a los operadores para cambiar de las clásicas asignaciones estáticas de recursos, donde los recursos utilizados para satisfacer la demanda eran fijos, a un enfoque dinámico, donde el sistema intenta acomodar los recursos para atender la demanda existente y adaptarse a entornos dinámicos. Uno de los problemas clave en este contexto es cómo vincular a los usuarios móviles a los satélites de manera eficiente en el tiempo, considerando las características de movilidad que poseen los usuarios móviles. Si bien existen numerosos trabajos que abordan ese problema, la complejidad e incertidumbre que agregan los usuarios móviles no ha sido suficientemente estudiada. Específicamente, argumentamos que los cambios inesperados de trayectoria y los retrasos en los usuarios móviles pueden hacer que las conexiones planificadas entre los usuarios y los satélites sean inviables. Esto es especialmente crítico con los usuarios aeronáuticos, que poseen patrones de movilidad rápida y se caracterizan por tener importantes retrasos y cambios de trayectoria. En vista de ello, proponemos una formulación de este problema que aborde a los usuarios móviles y sus características en constelaciones de satélites, y una forma de resolver el problema. Luego se realizan diferentes simulaciones para evaluar la validez del enfoque propuesto., El paradigma de les comunicacions per satèl·lit ha experimentat canvis dràstics en els últims anys. El comportament dels usuaris és cada vegada més difícil de caracteritzar, i l'augment de demanda de dades en qualsevol lloc i en qualsevol moment, està proporcionant al mateix temps noves oportunitats per al sector de les comunicacions per satèl·lit, així com nous reptes. D'altra banda, la millora del hardware i la flexibilitat en els sistemes de satèl·lits estan donant les eines als operadors de satèl·lits per canviar de les assignacions estàtiques clàssiques de recursos, on els recursos utilitzats per atendre la demanda és fixa, a un enfocament dinàmic, on el sistema intenta acomodar recursos per atendre la demanda existent i adaptar-se a entorns dinàmics. Un dels problemes clau en aquest context és com vincular els usuaris mòbils amb els satèl·lits de manera eficient en el temps, tenint en compte les característiques de mobilitat que tenen els usuaris mòbils. Encara que hi ha nombroses obres que aborden aquest problema, la complexitat i la incertesa afegides pels usuaris mòbils no han estat prou estudiades. Concretament, argumentem que els canvis inesperats de trajectòria i retards en els usuaris mòbils podrien fer inviables les connexions planificades entre usuaris i satèl·lits. Això és especialment crític amb els usuaris aeronàutics, que tenen patrons de mobilitat ràpida i es caracteritzen per tenir importants retards i canvis de trajectòria. En vista d'això, proposem una formulació d'aquest problema que abordi als usuaris mòbils i les seves característiques en les constel·lacions de satèl·lits, i una manera de resoldre el problema. A continuació, es realitzen diferents simulacions per avaluar la validesa de l'enfocament proposat.

This paper explores multi-satellite transmission schemes. The focus is on the multi-user downlink scenario, where two low Earth orbit satellites transmit data cooperatively, which are then combined at each of the ground user terminals. A single synchronization circuit is employed at the receiver to reduce the terminal burden. The orthogonal time and frequency space (OTFS) waveform is utilized to handle the residual offsets and schedule users on non-overlapping delay-Doppler resources. The paper leverages on OTFS, beam-centric compensation and the characteristics of the satellite channel to eliminate inter-user interference. Numerical results assess the effectiveness of the proposed scheme and highlight the improvement in performance achieved through satellite cooperation as compared to single satellite transmission., This paper is supported by PID2020-115323RB-C31 funded by MCIN/AEI/ 10.13039/501100011033 and MINECO/EU grant NextGenerationEU [UNICO-5G I+D/AROMA3D-SPACE (TSI-063000-2021-70)]., Peer Reviewed, Postprint (author's final draft)

Satellite Internet of Things (Sat-IoT) is a novel framework in which satellites integrate sensing, communication and computing capabilities to carry out task-oriented communications. In this paper we propose to use the Long Range (LoRa) modulation for the purpose of estimation in a Sat-IoT scenario. Then we realize that the collisions generated by LoRa can be harnessed in an Over-the-Air Computing (AirComp) framework. Specifically, we propose to use LoRa for Type-based Multiple Access (TBMA), a semantic-aware scheme in which communication resources are assigned to different parameters, not users. Our experimental results show that LoRa-TBMA is suitable as a massive access scheme, provides large gains in terms of mean squared error (MSE) and saves scarce satellite communication resources (i.e., power, latency and bandwidth) with respect to orthogonal multiple access schemes. We also analyze the satellite scenarios that could take advantage of the LoRa-TBMA scheme. In summary, that angular modulations, which are very useful in satellite communications, can also benefit from AirComp., This work is part of the project IRENE (PID2020-115323RB-C31), funded by MCIN/AEI/10.13039/501100011033 and supported by the Catalan government through the project SGR-Cat 2021-01207., Peer Reviewed, Postprint (author's final draft)

According to forecasts, around 10 billion connected devices in the world will exchange data over the Internet by2028 and the significant connections increase threatens to congest terrestrial networks. These devices will mainly beembedded, controlled by smart software and operated in the cloud, integrating the Internet of Things ecosystem. Addi-tionally, current terrestrial infrastructures do not meet novel IoT requirements: remote access areas, multiple networkdomains crossing and adaptable latency and bandwidth. To provide global and ubiquitous coverage, the 3GPP stan-dardizes in rel-17 the concept of Non-Terrestrial-Networks. The term includes, among others, Non-Terrestrial nodessuch as GEO, MEO and LEO satellites. Lately, LEO satellites have contributed to consolidate the New Space indus-try opening new business opportunities by providing services using low-cost CubeSats. Despite offering importantbenefits compared to GEO (e.g. lower latency and propagation loss), LEO still has challenges to face related to com-munication discontinuity (intermittent satellite-to-ground links). Global region coverage is achieved through satelliteconstellations; however, the main concern is the non-guarantee of simultaneous contact from UE to the Ground StationNetwork via the satellite. While 3GPP rel-17 specs have centered on the specification of satellites using transparentpayload, the use of regenerative payloads has not precluded and has a central role in the technology roadmap. Re-generative payloads envision to embark part of the NF within the satellite, giving multiple enhancements (e.g. lowerlatencies, Store-and-Forward operation, in-satellite local loop communications and edge computing). Onboard func-tions may include radio access functions, such as eNB/gNB, as well as core NF, which enables direct satellite responseto UE. This paper provides a performance analysis of a deployment of core NF in a regenerative payload with a Soft-ware Defined Radio based on FPGA technology, Peer Reviewed, Postprint (published version)

The current trend of the space industry regarding Earth Observation (EO) and Telecommunications satellites is to keep lowering the orbit to increase the resolution of the images, to have a better Signal to Noise Ratio (SNR), or to have a lower latency in communications, among others things. Very Low Earth Orbits (VLEO) also offers the possibility to use the increased atmospheric density at low altitudes for novel purposes like aerodynamics-based attitude control. However, flying a satellite in VLEO is a technological challenge because atmospheric density is much higher in VLEO. To maintain a long-term mission, huge amounts of propellant would be needed if current propulsion systems were to be used. A possible solution to extend the lifetime of such missions is Atmosphere-Breathing Electric Propulsion (ABEP) that collects atmospheric particles (e.g. atomic oxygen) by an intake and feeds an electric thruster which ionizes and accelerates them to generate thrust. That is what Kreios Space is working on. They are developing an innovative all-electric propulsion system that would not need to carry propellant. On the context of the Kreios Space mission, this project aims to develop a satellite simulator for the Attitude Determination and Control Subsystem (ADCS) for this new satellite prototype. The simulator is developed in MATLAB Simulink. It is a very simple first approach of the subsystem. It aims to develop the bases of the subsystem to then, add new functionalities and make it more accurate as the satellite is developed. The simulator will basically contain the main components in any controlled system, which are: a reference, a controller, the actuators, and the model of the system, which includes the dynamics of the satellite. Additionally, a 3D visualisation block to see the satellite dynamics has been added. Once the simulator is developed, three different studies are carried out. The first one is related with VLEO disturbances. It demonstrates that other disturb

LEO satellite networks have become a growing item of interest in the last years. This new technology will revolutionize the internet, allowing communications all along the globe. Furthermore, thanks to LEO networks, it will now become possible to track flying aircraft with global coverage. Previous to LEO and GEO satellite networks, airlines did not have means to properly track aircraft flying through inter-oceanic routes. Hence, this technology will improve safety and reliability levels of aviation all over the world. As a result, air traffic is expected to be optimised, which shall in turn, allow to fly more sustainably. Such interest in this new technology has motivated the development of this project. The aim of this thesis is to design and implement an aircraft mobile node module for the SILLEO-SeamSAT constellation simulator, which would allow to study communications between aircraft and LEO satellite networks. For this purpose, a software tool has been developed in order to save and process real flights which shall be uploaded to the simulator. The results of this project will allow to determine the viability and performance of communications between aircraft and LEO satellite networks with global coverage.

En los últimos años, el número de satélites en el espacio ha crecido debido a la demanda de servicios basados en satélites. Los satélites pueden proporcionar distintos servicios, como por ejemplo, proporcionar servicios de telecomunicaciones (como telefonía, televisión, transmisión de datos, etc), observación de la Tierra, navegación y posicionamiento, meteorología, etc. Hasta el momento, la comunicación entre estaciones terrenas y satélite o entre satélites se ha basado en una comunicación por enlace RF. Sin embargo, recientemente ha despertado la necesidad de mejorar el sistema y permitir el intercambio de una mayor información en los enlaces de subida y bajada (Bit Rate). Además, el gran número de satélites orbitando la Tierra con diferentes finalidades afecta a la disponibilidad limitada del espectro de RF, la cual está firmemente regulada. De esta manera nace un nuevo tipo de comunicación basado en enlaces ópticos (Free Space Optic, FSO). Las comunicaciones FSO utilizan luz láser para transmitir información. Estas señales son transmitidas por un haz de luz que se propaga a través del espacio y es capturado por un receptor óptico. La ventaja de las comunicaciones FSO es que pueden transmitir grandes cantidades de información a velocidades extremadamente altas, superando incluso a las comunicaciones RF. Además, las señales FSO son inmunes a las interferencias electromagnéticas y son muy difíciles de interceptar, lo que las hace altamente seguras. Con el objetivo de analizar el comportamiento de las comunicaciones FSO, y realizar una comparación a nivel técnico y económico con las comunicaciones RF, surge el presente proyecto. En este, se ha propuesto una misión, la cual puede ser llevada a cabo por 4 casos distintos que combinan comunicaciones RF y FSO, además de distintas configuraciones orbitales. Esta misión se basa en el envío de información que una estación en Amazonas recibe (fotos, vídeos, datos, etc). La información enviada desde la estación en Amazonas s

In the present thesis, a MatLab simulator originally designed to calculate connections between satellites and ground stations has been expanded to include airplane routes and their respective connections. The goal is to provide an accurate and efficient ground-air-space simulation tool for monitoring air connections, which will allow for improved air traffic efficiency and safety. Air transportation is one of the most widely used modes of transportation worldwide, and its efficiency and safety are of vital importance. Using satellites for monitoring airplanes is of utmost importance due to several reasons, including the ability to provide continuous global coverage, real-time data on aircraft parameters, improved air traffic management, and enhanced safety. The designed tool allows for the simulation of multiple aeroplanes and satellites, and automatically calculates the connections between aircraft and satellites and between satellites and ground stations. In addition, a module has been added to simulate and calculate connections between aircraft and ground stations. This project is part of the PLATHON project of the Polytechnic University of Catalonia, which aims to develop a simulator to study the communications between constellations of cubes and the Earth. The simulator developed in this thesis will be used as a basis for the study of the communication between cubes, airplanes and ground in the PLATHON project. Testing and validation of the simulator have been conducted, and it has been demonstrated to be an effective tool for simulating and monitoring air connections. In conclusion, this project represents a significant advance within the PLATHON project in the monitoring of air connections, and has proven to be a very useful and necessary tool for monitoring aircraft routes across the globe.

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)., Peer Reviewed, Postprint (author's final draft)

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., Peer Reviewed, Postprint (author's final draft)

This article addresses the problem of energy and code allocation to many users accessing, under spreading-based nonorthogonal multiple access, a wireless node set up with a successive interference cancellation architecture aided by redundancy-check error control. As an application, we consider the asynchronous access of a delay-tolerant satellite system, where users employ finite-length channel codes and are subject to a known power unbalance induced by the known distribution of the channel’s attenuation. The article develops, as a mathematically tractable approximation to massively populated systems, a unified framework to compute the best energy and code allocation rules that maximize the spectral efficiency of a network that handles asymptotically many users. Concretely, the presented approach circumvents the exponential complexity in the number of users when modeling the propagation of packet decoding failures through the receiver’s decoding scheme. It also enables a deterministic analysis of the more complex features affecting the receiver, making the related performance optimization problem amenable to systematic tools from differential and variational calculus. The derived expressions evidence the most favorable three-way unbalance between energy, rate, and reliability for receiver performance. Low-level system simulations are carried out for validation., This work was supported in part by the Spanish Ministry of Science and Innovation through project RODIN (PID2019-105717RB-C22/AEI/10.13039/501100011033) and in part by Grant 2017 SGR 578., Peer Reviewed, Postprint (published version)

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.

NASA JPL ha dissenyat un nou model numèric determinístic de propagació per carac- teritzar el canal entre un transmissor a la Lluna i un receptor a la Terra. En concret, el transmissor pot ser un rover o una estació base a la superfície i el receptor serà generalment una antena de la Deep Space Network (DSN). El model té en compte les reflexions provo- cades per la superfície lunar i obté la caracterització completa de la propagació del retard i del Doppler, entre d’altres aspectes d’interès com la potència rebuda total de les reflexions, etc. Les entrades del model són la definició de la superfície lunar amb un Digital Elevation Map i de la rugositat del sòl amb els paràmetres del RMS del pendent, entre d’altres. El càlcul de les reflexions multicamí es duu a terme a través d’una discretització del mapa en facetes i amb l’aproximació de rajos de Geometria Òptica. Seguidament, es valida el model en dos passos. El primer, veure l’ajust entre la simplifi- cació teòrica d’un model de dos rajos (raig directe en línia de visió i un únic raig reflectit) modelant la Lluna com una esfera perfecta i llisa. El segon, verificar els resultats del model en un cas real comparant-los amb les dades empíriques disponibles mesurades a través de la DSN i el Lunar Reconaissance Orbiter (LRO). Els resultats obtinguts es mostren en gràfiques comparatives i amb mètriques com ara el progrés de la propagació del Doppler en funció del temps., NASA JPL ha diseñado un nuevo modelo numérico determinístico de propagación para caracterizar el canal entre un transmisor en la Luna y un receptor en la Tierra. En concreto, el transmisor puede ser un rover o una estación base en la superficie y el receptor será generalmente una antena de la Deep Space Network. El modelo contempla las reflexiones provocadas por la superficie lunar y obtiene la caracterización completa de la propagación del retraso y del Doppler, entre otros aspectos de interés como la potencia recibida total de las reflexiones, etc. Las entradas del modelo son la definición de la superficie lunar con un Digital Elevation Map y de la rugosidad del suelo con los parámetros del RMS de la pendiente, entre otros. El cálculo de las reflexiones multicamino se realiza a través de una discretización del mapa en facetas y con la aproximación de rayos de Geometría Óptica. Seguidamente, se valida el modelo en dos pasos. El primero, ver el ajuste entre la simplificación teórica de un modelo de dos rayos (rayo directo en línea de visión y un único rayo reflejado) modelando la Luna como una esfera perfecta y lisa. El segundo, verificar los resultados del modelo en un caso real comparándolos con los datos empíricos disponibles medidos a través de la DSN i el Lunar Reconaissance Orbiter (LRO) Los resultados obtenidos se muestran en gráficas comparativas y con métricas como el progreso de la propagación del Doppler en función del tiempo., NASA JPL designed a new deterministic numerical propagation model to characterize the channel between a transmitter on the Moon and a receiver on Earth. Specifically, the transmitter may be a rover or a surface base station, and the receiver will generally be a Deep Space Network (DSN) antenna. The model takes into account the reflections caused by the lunar limb and obtains the complete characterization of the delay and Doppler spread, among other aspects of interest such as the total received power of the reflections, etc. The model inputs are the definition of the lunar surface with a Digital Elevation Map, and the roughness of the ground specified using parameter such as the slope Root Mean Square, among others. The calculation of the multipath reflections is carried out through a discretization of the map in facets and using the Geometric Optics approximation. The model is validated in two steps. First, it is compared the fit between the theoretical simplification of a two-ray model (direct ray in line of sight and a single reflected ray) assuming the Moon is a perfect, smooth sphere. Second, the results of the model are verified in a real case by comparing them with the available empirical data measured using the DSN and the Lunar Reconaissance Orbiter (LRO). The results obtained are shown in comparative graphs and with metrics such as the evolution of the Doppler spread as a function of time.

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.

El present treball ha estat realitzat durant una estància de pràctiques a Sener Aeroespacial, una empresa del sector espacial que es dedica al desenvolupament de subsistemes de comunicacions per a satèl·lits científics i comercials. En aquest es descriu el disseny, anàlisi, mesures y resultats d’un generador de polsos de corrent que permet la commutació de circuladors amb guia de ferrita, i el disseny i anàlisi de circuits que permeten alimentar els dissenys de radiofreqüència. Ambdós formen tota la PCB d’alimentació i control del radiòmetre que s’embarcarà a la missió espacial CIMR (Copernicus Imaging Microwave Radiometer). El document comença amb una primera introducció a la missió i el satèl·lit, seguit d’un resum dels diferents commutadors de radiofreqüència utilitzats actualment. A continuació, es mostren tres blocs: el disseny electrònic, els anàlisi del disseny segons els estàndards de l’Agència Espacial Europea, i el disseny de la PCB. Finalment, el disseny final del generador de polsos és implementat i, al mateix temps, es detallen els procediments de mesura i els resultats obtinguts., El presente trabajo ha sido realizado durante una estancia de prácticas en Sener Aeroespacial, una compañía del sector espacial que se dedica al desarrollo de subsistemas de comunicaciones para satélites científicos y comerciales. En él se describe el diseño, análisis, medida y resultados de un generador de pulsos de corriente que permite la conmutación de circuladores en guía de ferrita, y el diseño y análisis de la circuitería que permite alimentar los diseños de radiofrecuencia. Ambos forman toda la PCB de alimentación y control del radiómetro que se embarcará en la misión espacial CIMR (Copernicus Imaging Microwave Radiometer). El documento comienza con una primera introducción a la misión y al satélite, seguido de un resumen de los diferentes conmutadores de radiofrecuencia usados actualmente. A continuación, se muestran tres bloques: el diseño electrónico, los análisis del diseño según los estándares de la Agencia Espacial Europea, y el diseño de la PCB. Finalmente, el diseño final del generador de pulsos es implementado y, al mismo tiempo, se detallan los procedimientos de medida y los resultados obtenidos., This work has been carried out during an internship at Sener Aeroespacial, a space dedicated company that deals with the development of communications subsystems for scientific and commercial satellites. It describes the design, analysis, measurements, and results of a current pulse generator that enables the switching of waveguide ferrite circulators, and the circuitry design and analysis to correctly bias the Radio Frequency equipment. Both form the entire power and control PCB for the radiometer that will be embarked on the CIMR (Copernicus Imaging Microwave Radiometer) space mission. The document starts with a first introduction to the mission and the satellite, followed by a brief summary of the different RF switches currently in use. Next, three blocks are shown: the electronic design, the design analyses according to European Space Agency standards, and the PCB design. Finally, the final design of the pulse generator is implemented, and the measurement procedures, as well as the results obtained, are detailed and discussed.

Els nivells de flexibilitat i escalabilitat mai vistos de la propera generació de sistemes de comunicació per satèl·lit exigeixen nous algorismes de gestió de recursos que s'adaptin a contextos dinàmics. El futur entorn dels serveis de comunicació per satèl·lit estarà definit per un nombre més gran d'usuaris, una gran part dels quals correspondrà a usuaris mòbils com avions o vaixells. El repte addicional que introdueixen aquests usuaris és abordar la incertesa espai-temporal que es presenta en forma de retards, canvis en la seva trajectòria, o tots dos. Atès que els usuaris mòbils constituiran un segment important del mercat, els operadors de satèl·lits prioritzen l'aprofitament dels avançats sistemes digitals per desenvolupar estratègies flexibles d'assignació de recursos que siguin robustes davant de les bases d'usuaris dinàmiques. Un dels problemes clau en aquest context és com gestionar l'espectre de freqüències de manera eficient. Mentre que nombroses solucions aborden escenaris d'assignació de dinàmica freqüències, el nivell addicional de complexitat que presenten els usuaris mòbils no ha estat prou estudiat, i no és clar si els nous algorismes d'assignació de freqüències poden abordar la incertesa espai-temporal. Concretament, sostenim que els canvis inesperats en la posició dels usuaris introdueixen noves restriccions en l'assignació de freqüències que els algoritmes la literatura podrien no ser capaços de complir, especialment si les decisions s'han de prendre en temps real i a escala. Per solucionar aquesta limitació, proposem un algorisme de gestió dinàmica de freqüències basat en programació lineal entera que assigna recursos a escenaris amb usuaris tant fixos com mòbils, tenint en compte la incertesa espai-temporal d'aquests últims. El nostre mètode inclou tant la planificació a llarg termini com l'operació en temps real, una sinergia que no ha estat prou explorada per a les comunicacions per satèl·lit i que és crítica quan s'opera sota incertesa. P, Los niveles de flexibilidad y escalabilidad nunca vistos de la próxima generación de sistemas de comunicación por satélite exigen nuevos algoritmos de gestión de recursos que se adapten a contextos dinámicos. El futuro entorno de los servicios de comunicación por satélite estará definido por un mayor número de usuarios, una gran parte de los cuales corresponderá a usuarios móviles como aviones o barcos. El reto adicional que introducen estos usuarios es abordar la incertidumbre espacio-temporal que se presenta en forma de retrasos, cambios en su trayectoria, o ambos. Dado que los usuarios móviles constituirán un segmento importante del mercado, los operadores de satélites dan prioridad al aprovechamiento de los avanzadas sistemas digitales para desarrollar estrategias flexibles de asignación de recursos que sean robustas frente a las bases de usuarios dinámicas. Uno de los problemas clave en este contexto es cómo gestionar el espectro de frecuencias de forma eficiente. Mientras que numerosas soluciones abordan escenarios de asignación dinámica de frecuencias, el nivel adicional de complejidad que presentan los usuarios móviles no ha sido suficientemente estudiado, y no está claro si los nuevos algoritmos de asignación de frecuencias pueden abordar la incertidumbre espacio-temporal. En concreto, sostenemos que los cambios inesperados en la posición de los usuarios introducen nuevas restricciones en la asignación de frecuencias que los algoritmos la literatura podrían no ser capaces de cumplir, especialmente si las decisiones deben tomarse en tiempo real y a escala. Para solventar esta limitación, proponemos un algoritmo de gestión dinámica de frecuencias basado en la programación lineal entera que asigna recursos en escenarios con usuarios tanto fijos como móviles, teniendo en cuenta la incertidumbre espacio-temporal de estos últimos. Nuestro método incluye tanto la planificación a largo plazo como la operación en tiempo real, una sinergia que no ha sido suficient, The unprecedented levels of flexibility and scalability of the next generation of communication satellite systems call for new resource management algorithms that adapt to dynamic environments. The upcoming landscape of satellite communication services will be defined by an increased number of unique users, a large portion of which will correspond to mobile users such as planes or ships. The additional challenge introduced by these users is addressing the spatiotemporal uncertainty that comes in the form of delays, changes in their trajectory, or both. Given that mobile users will constitute an important segment of the market, satellite operators prioritize leveraging modern digital payloads to develop flexible resource allocation strategies that are robust against dynamic user bases. One of the key problems in this context is how to manage the frequency spectrum efficiently. While numerous solutions address dynamic frequency assignment scenarios, the additional layer of complexity presented by mobile users has not been sufficiently studied, and it is unclear whether novel frequency assignment algorithms can address spatiotemporal uncertainty. Specifically, we argue that unexpected changes in the position of users introduce new restrictions into the frequency assignment, which previous algorithms in the literature might not be able to meet, especially if decisions need to be made in real-time and at scale. To address this gap, we propose a dynamic frequency management algorithm based on integer linear programming that assigns resources in scenarios with both fixed and mobile users, accounting for the spatiotemporal uncertainty of the latter. Our method includes both long-term planning and real-time operation, a synergy that has not been sufficiently explored for satellite communications and proves to be critical when operating under uncertainty. To fulfill the problem’s scope, we propose different strategies that extend a state-of-the-art frequency management alg, Outgoing

The use of Signals of Opportunity for Earth Observation is a hot topic nowadays. It consists of using signals already used for some purposes for other purposes, like remote sensing or navigation. The thesis mixes this concept with signals from P-band, a really interesting band because they can penetrate more than 20 cm in the soil, before being reflected, allowing us to estimate root-zone soil moisture values. The main objective of the project is to design a receiving system for Signals of Opportunity at P-band based on Software Defined Radio. This thesis reviews all the necessary parts of the whole system and the necessary software setup to have a complete receiver. On the other hand it has some results recorded for testing the receiving system and results of the process of finding suitable signals of Opportunity to develop our reflectometry studies with also a curious report on Intermodulation Distortion components being surprisingly well received. Results indicate that the receiving system works, but that the received interferences are a problem for the thesis objective, and further tests on different locations with different setups are needed to start having a first estimation of the root-zone soil moisture., El uso de Señales de Oportunidad para la teledetección es un tema de relevancia actualmente, consiste en usar señales preconcebidas para otras finalidades para tus propies intereses, como teledetección o para usar de señal de navegación. La tesis mezcla ese concepto con señales de banda P, una banda de frecuencias realmente interesante por el hecho de que las frecuencias que pertenecen a la banda son capaces de penetrar unos 20 cm en la tierra antes de reflejarse, permitiéndonos estimar valores de humedad en las raíces de la vegetación. El objetivo principal del proyecto es diseñar un sistema de recepción para señales de oportunidad en la banda P basado en una Radio Definida por Software (SDR). La tesis repasa todas las partes necesarias que componen el sistema entero y el software necesario para tener el setup del sistema de recepción completo. Por otro lado, incluye resultados grabados para probar el funcionamiento del sistema de recepción y el resultado del proceso de encontrar señales de oportunidad adecuadas para desarrollar estudios de reflectometría. La tesis también incluye un reporte curioso sobre Productos de Intermodulación siendo recibidos correctamente. Los resultados indican que el sistema de recepción funciona, pero las interferencias recibidas son un problema para los objetivos del proyecto. También indican que más test en diferentes localizaciones con diferentes configuraciones son necesarios para empezar a tener estimaciones de valores de humedad en las raíces de vegetación., L'ús de Senyals d'Oportunitat per a la teledetecció és un tema de rellevància actualment, consisteix a utilitzar senyals preconcebuts per altres finalitats pels teus propis interessos, com teledetecció o per utilitzar de senyals de navegació. La tesi combina aquest concepte amb senyals de banda P, una banda de freqüències realment interessants pel fet que les freqüències que pertanyen a aquesta banda estan capacitades de penetrar uns 20 cm a la terra abans de reflectir-se, permetent estimar valors d'humitat a les arrels de la vegetació. L'objectiu principal del projecte és dissenyar un sistema de recepció per senyals d'oportunitat a la banda P basat en una Ràdio Definida per Software (SDR). La tesi repassa totes les parts necessàries que componen el sistema sencer i el software necessari per tenir el "setup" del sistema de recepció complet. Per altra banda, inclou resultats gravats per provar el funcionament del sistema de recepció i el resultat del procés de trobar senyals d'oportunitat adequats per desenvolupar estudis de reflectometria. La tesis també aporta un informe curiós sobre Productes d'Intermodulació sent rebuts correctament. Els resultats indiquen que el sistema de recepció funciona, però les interferències rebudes són un problema pels propòsits del projecte. També indiquen que més test a diferents localitzacions amb diferents configuracions són necessaris per començar a tenir estimacions de valors d'humitat en les arrels de la vegetació.

In the field of space travel, space communications has always presented a slew of obstacles and hurdles that must be overcome in order to complete a successful mission. Space limits inside a satellite or spaceship, vast distances between satellites and ground stations, and a phenomenon known as "Faraday Rotation" in the ionosphere are only a few of the most typical issues. Satellite antennas must be small, compact, efficient, and circularly polarized as a result of the aforementioned issues. The helix antenna is an excellent answer for all of the requirements. In this work we develop a deployment and pointing mechanism of a helix antenna operated with software defined radio algorithms. The features of helix antennas are exceptional, and they are especially suitable for satellite communication. Three coaxial cylinders, two stepper motors, one pulley, and one thread make up a deployment-pointing mechanism. The mechanism deploys the antenna along its longitudinal axis and turns it horizontally towards the ground station. During the flight, the antenna is deployed and retracted. Under different positioning situations, the GPS, an altimeter, and a compass calculate the gondola's position in order to rotate the antenna towards the Ground Station and close the communication link. The antenna's rotation mechanism is triggered by the integrated attitude determination and control system algorithms in order to correct the pointing and orientation towards the Ground Station. The antenna uses software defined radio algorithms to achieve weight and volume reductions while maintaining high efficiency and reconfigurability. The experiment includes a high-definition camera that provides real-time information on the antenna's orientation and condition. SHADE's flight on the BEXUS 28/29 balloon resulted in effective deployment and transmission, as well as the ability to receive and decode transmitted packets. The rotating mechanism met the pointing requirements, and all of the sensor'

This paper addresses general space education for interdisciplinary audiences. In particular, this paper considers education in the field of Satellite Telecommunications (Sat-Comms). The challenge in presenting the field of sat-comms for effective learning is two-fold. Firstly, this field is interdisciplinary, the disciplines are coupled, and it is complex. Secondly, the typical audiences for this subject often have diverse backgrounds. Hence, a suitable teaching strategy is required, so that all students can learn from a training session. Publicly available sat-comms training is largely engineering focused. This study could not find suitable training for the purpose of interdisciplinary sat-comms education. Hence, to address this absence in available training, the author has created a workshop, which provides sat-comms education to interdisciplinary audiences. The workshop was empirically developed from the author’s experience at Inmarsat and at the International Space University. The workshop uses elements from Constructivist, Behaviourism, Cognitive, Connectivism, and Experiential learning theories. Furthermore, it was designed to be taught in person and online. The Sat-Comms Game was first trialled in an online format in 2021. The workshop worked well in engaging the participants during the session. Additionally, feedback on the workshop was positive. Hence, this trial indicated that the workshop could function logistically and engage people pedagogically. The author intends to conduct further trials and corresponding assessment methods to gauge the pedagogic effectiveness

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., Peer Reviewed, Postprint (author's final draft)

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.

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)), Peer Reviewed, Postprint (author's final draft)

The Remote sensing and Interference detector with radiomeTry and vegetation Analysis (RITA) is a 1U payload that will fly onboard Alainsat-1, a 3U CubeSat. Among other experiments, it will perform a proof of concept of a LoRa custom module for space-to-Earth communications between the satellite and a terrestrial network of Internet of Things sensors. This final degree thesis consists of the implementation of the protocols of the Media Access Control layer that will be used in the experiment mentioned above, precisely in the design, implementation, and testing of pure ALOHA, and the design of CSMA/CA with RTS/CTS., El sensor Remoto y detector de Interferencias por radiomeTría i Análisis de vegetación (RITA), es una carga útil de 1U que volará a bordo del CubeSat AlainSat-1 de 3 Unidades. De entre otros experimentos, ésta realizará una prueba de concepto de la utilización de un módulo LoRa desarrollado en la UPC para las comunicaciones espacio-tierra entre el satélite i una red terrestre de sensores de internet de las cosas. Este trabajo final de grado consiste en la implementación de los protocolos de la capa de control de acceso al medio que se utilizaran en el experimento mencionado anteriormente; concretamente en el diseño, implantación i testeo del ALOHA puro, i el diseño del CSMA/CA con RTS/CTS., El sensor Remot i detector d'Interferències per a radiomeTria i Anàlisi de vegetació (RITA), és una càrrega útil de 1U que volarà a bord del CubeSat de 3 Unitats Alainsat-1. Entre d'altres experiments, aquesta realitzarà un prova de concepte de la utilització d'un mòdul LoRa desenvolupat a la UPC per a comunicacions espai-terra entre el satèl·lit i una xarxa terrestre de sensors d'internet de les coses. Aquest treball final de grau consisteix en la implementació dels protocols de la capa de control d'accés al medi que s'utilitzaran en l'experiment mencionat anteriorment; concretament amb el disseny, implementació i test de l'ALOHA pur, i el disseny del CSMA/CA amb RTS/CTS.

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

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., Peer Reviewed, Postprint (published version)

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.

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.

The low earth orbit (LEO) satellite system is one of the promising solutions to provide broadband services to a wide-coverage area for future integrated LEO-6G networks, where users' demands vary with time and geographical locations. Conventional satellites with fixed beam pattern and footprint planning may not be capable of meeting such dynamic requests and irregular traffic distributions. As the development of flexible satellite payload with beamforming capabilities, spot beams with flexible size and shape are considered potential solutions to this issue. As an early investigation, in this paper, we consider the scenarios where satellite payloads are equipped with multiple beam patterns and study the optimal beam pattern selection. We exploit the potential synergies of joint resource optimization between adaptive beam patterns and non-orthogonal multiple access (NOMA) in a LEO satellite system, where NOMA is employed to reduce intra-beam interference and flexible beam pattern is adopted to mitigate inter-satellite interference. The formulated problem is to minimize the capacity-demand gap of terminals, which falls into mixed-integer nonconvex pro-gramming (MINCP). To tackle the discrete variables and non-convexity, we design a joint approach to allocate power and select beam patterns. Numerical results show that the proposed scheme achieves capacity-demand gap reduction of 37.8% over conventional orthogonal multiple access (OMA) and 42.5% over the fixed-beam-pattern scheme., This work has been supported by the Luxembourg national research fund (FNR) under the project ROSETTA (C17/IS/11632107) and MegaLEO (C20/IS/14767486)., Peer Reviewed, Postprint (author's final draft)

Currently, about 40% of the world’s population has limited or no access to high-speed Internet. Especially in rural, hard-to-reach areas, there is a challenge in terms of infrastructure to guarantee a quality connection.The need for global coverage has led telecommunications service providers to explore new alternatives to traditional communication. This search has led to the development of a multitude of projects related to satellite constellations in LEO orbits, where a more economical business model has been found, capable of providing global coverage and high-speed connection. The growing interest in LEO communications has motivated this project. The objective of this thesis is to study communication links in a LEO constellation through link budget calculations. Both inter-satellite links and ground-satellite links will be evaluated in order to study the characteristics of each one. For this purpose, an orbit simulator has been used, where the necessary calculations have been introduced to evaluate the links according to parameters such as received power and SNR, among others. The results of this project are expected to determine the viability of communications in a constellation and the effect of the link budget parameters on the communications performance.

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)., Peer Reviewed, Postprint (published version)