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Emerging integrated satellite-drone-terrestrial communication (ISDTC) technologies are expected to contribute to our life by bringing forth high speed wireless connectivity to every corner of the world. On the one hand, the Internet of Things (IoT) provides connectivity to various physical objects by enabling them to share information and to coordinate decisions. On the other hand, the non-terrestrial components of an ISDTC system, i.e. unmanned aerial vehicles (UAVs), and satellites, can boost the capacity of wireless networks by providing services to hotspots, disaster affected, and rural areas. Despite the several benefits and practical applications of ISDTC technologies, one must address many technical challenges such as, resource management, trajectory design, device cooperation, data routing, and security. The key goal of this dissertation is to develop analytical foundations for the optimization of ISDTC operations, and the deployment of non-terrestrial networks (NTNs). First, the problem of resource management within ISDTC systems is investigated for service-effective cooperation among the terrestrial networks and NTNs. The performance of a multi-layer ISDTC system is analyzed within a competitive market setting.Using a novel decentralized algorithm, spectrum resources are allocated to each one of the communication links, considering the fairness among devices. The proposed algorithm is proved to reach a Walrasian equilibrium, at which the sum-rate of the network is maximized. The results also show that the proposed algorithm can reach the equilibrium with a practical convergence speed. Then, the effective deployment of NTNs under environmental dynamics is investigated using machine learning solutions with meta training capabilities. First, the use of satellites for on-demand coverage to unforeseeable radio access needs is investigated using game theory. The optimal data routing strategies are learned by the satellite system, using a novel reinforcement learning approach with distribution-robust meta training capability. The results show that, the proposed meta training mechanism significantly reduces the learning cost on the satellites, and is guaranteed to reach the maximal service coverage in the system. Next, the problem of control of UAV-carried radio access points under energy constraints is studied. In particular, novel frameworks are proposed to design trajectories for UAVs that seek to deliver data service to distributed, dynamic, and unforeseeable wireless access requests. The results show that the proposed approaches are guaranteed to converge to an optimal trajectory, and can get a faster convergence speed and lower computation cost using decomposition, cross validation and meta learning. Finally, this dissertation looks at the security of an IoT system. In particular, the impact of human intervention on the system security is analyzed under specific resource constraints. Psychological game theory frameworks are proposed to analyze the human psychology and its impact on the security of the system. The results show that the proposed solution can help the defender optimize its connectivity within the IoT system by estimating the attacker's behavior. In summary, the outcomes of this dissertation provide key guidelines for the effective deployment of ISDTC systems. / Doctor of Philosophy / In the past decade, the goal of providing wireless connectivity to all individuals and communities, including the most disadvantaged ones, has become a national priority both in the US and globally. Yet, remarkably, until today, there is still a great portion of the Earth's population who falls out of today's wireless broadband coverage. While people who live in under-developed or rural areas are still in "wireless darkness", communities in megacities often experience below-par wireless service due to their overloaded communication systems. To provide high-speed, reliable wireless connectivity to those on the less-served side of the digital divide, an integrated space-air-ground communication system can be designed. Indeed, airborne and space-based non terrestrial networks (NTNs) can enhance the capacity and coverage of existing wireless cellular networks (e.g., 5G and beyond) by providing supplemental, affordable, flexible, and reliable service to users in rural, disaster affected, and over-crowded areas. In order to fill the coverage holes and bridge the digital divide, seamless integration among NTNs and terrestrial networks is needed. In particular, when deploying an integrated communication system, one must consider the problems of spectrum management, device cooperation, trajectory design, and data routing within the system. Meanwhile, with the increased exposure to malicious attacks on high altitude platforms and vulnerable IoT devices, the security within the integrated system must be analyzed and optimized for reliable data service. To overcome all the technological challenges that hinder the realization of global digital inclusion, this dissertation uses techniques from the fields of game theory, meta learning, and optimization theory to deploy, control, coordinate, and manage terrestrial networks and NTNs. The anticipated results show that a properly integrated satellite-drone-terrestrial communication (ISDTC) system can deliver cost-effective, high speed, seamless wireless service to our world.

International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California / The Near Earth Asteroid Rendezvous (NEAR) satellite will travel to the asteroid 433 Eros, arriving there early in 1999, and orbit the asteroid for 1 year taking measurements that will map the surface features and determine its elemental composition. NEAR is the first satellite to use the rate-1/6 convolutional encoding on its telemetry downlink. Due to the scarcity and complexity of full decoders, APL designed and built a less capable but inexpensive version of the decoder for use in the integration, test, and prelaunch checkout of the rate-1/6 encoder. This paper describes the rationale for the design, how it works, and the features that are included.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: A low earth orbit satellite system can be useful in numerous communication applications where physical connections are not possible. Communication time available from any point on earth to the satellite is less than one hour per day. This one hour is fragmented into smaller time slots due to the satellite orbiting. This is not much time to transfer data and there is even less time available to transfer data when there are other external factors affecting the system. It is thus crucial to optimise the satellite communications link so that more data can be transferred per orbit. The goal of this thesis is to improve the performance of a low earth orbit satellite communication channel by varying certain parameters of the system, such as the protocol used, modulation scheme, packet size, transmission power etc. and then to observe how these parameters influence the system. The protocols that were chosen to be implemented are CSMA-CA, CSMA-CA with DSSS technology and Round-Robin Polling. A simulator for each protocol was designed with the Opnet platform, so that specific parameters could be changed and the results observed, in order to optimise the communications link between the satellite and ground stations. The results showed that there is no particular configuration of modulation scheme, packet size, transmission power etc. presenting the best overall solution for LEO satellite communications. It must be considered what the specific LEO satellite application would be used for and the characteristics required by that specific application. A suitable configuration must subsequently be chosen from the set of configurations available to satisfy most of the application requirements. / AFRIKAANSE OPSOMMING: ’n Satelliet met ’n lae wentelbaan kan gebruik word in verskeie kommunikasie toepassings waar fisiese verbindinge nie noodwendig moontlik is nie. Die kommunikasietyd van enige punt van aarde af na die satelliet, is minder as een uur per dag. Hierdie tyd word nog verder verklein omdat die satelliet besig is om, om die aarde te wentel. ’n Uur is glad nie baie tyd om data oor te dra nie en in realiteit is daar nog minder tyd beskikbaar as daar eksterne faktore op die sisteem inwerk. Dus is dit baie belangrik om die satelliet kommunikasiekanaal te optimiseer sodat soveel moontlik data as moontlik oorgedra kan word per omwenteling. Die doel van hierdie tesis is om die deurset van die kommunikasiekanaal van n lae wentelbaan satelliet te optimiseer, deur verskeie parameters te verander soos, protokol wat gebruik word, modulasie skema, pakkie grootte, transmissiekrag ens. en dan waar te neem hoe dit die sisteem beïnvloed. Die protokolle wat geïmplementeer is, is CSMA-CA, CSMA-CA met DSSS tegnologie en Round-Robin Polling. ’n Simulator vir elke protokol was ontwerp in die Opnet simulasie platform, sodat die spesifieke parameters verander kon word om die resultate te bestudeer met die doel om die kommunikasiekanaal tussen die satelliet en grond stasies optimaal te benut. Die resultate het bewys dat daar geen spesifieke konfigurasie van modulasie skema, pakkie grootte, transmissiekrag ens. is wat die algehele beste oplossing is nie. Die spesifieke applikasie waarvoor die lae wentelbaan satelliet gaan gebruik word moet geanaliseer word sowel as die spesifieke karakteristieke van daai applikasie. Daarvolgens moet n unieke konfigurasie opgestel word wat meeste van die applikasie se behoeftes bevredig.

In satellite communications, non-linear interference is created by the non-linear power amplifier aboard the satellite. Even in the case of a memoryless power amplifier, the channel is a non-linear system with memory due to the presence of linear filters on ground and aboard the satellite. The non-linear interference degrades the system performance, especially when considering high-order modulations or in case of several signals being amplified by the same power amplifier. In this thesis, we have proposed algorithms at the transmitter and at the receiver to digitally compensate this interference. In particular, a new predistortion algorithm has been proposed, which significantly improves state-of-the-art algorithms. Since the complexity of this algorithm is an issue, low-complexity algorithms have also been proposed and achieve almost the same performance as the initial algorithm. We have also proposed joint predistortion and turbo-equalization algorithms to further improve the system performance. / En communications par satellite, de l’interférence non-linéaire est créée par l’amplificateur de puissance non-linéaire à bord du satellite. Même si l’amplificateur peut être considéré comme sans mémoire, le canal est malgré tout un système non-linéaire avec mémoire de par la présence de filtres linéaires au sol ou à bord du satellite. L'interférence non-linéaire dégrade les performances du système, en particulier lorsqu’on considère des modulations d’ordre élevé ou plusieurs signaux amplifiés par le même amplificateur de puissance. Dans cette thèse, nous avons proposé des algorithmes à l’émetteur et au récepteur pour compenser numériquement cette interférence. En particulier, nous avons proposé un nouvel algorithme de prédistorsion qui améliore de façon significative les algorithmes de l’état-de-l’art. La complexité de l’algorithme étant très élevée, nous avons proposé des algorithmes de plus faible complexité atteignant pratiquement les mêmes performances par rapport à l’algorithme initial. Nous avons aussi proposé des algorithmes de prédistorsion et d’égalisation conjointes, permettant d'atteindre des performances plus élevées qu'avec la prédistorsion seule. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

Målsättningen med examensarbetet är att utvärdera en metod för att upprätta en kommunikationslänk från en mobil satellitterminal till en geostationär kommunikationssatellit utan kännedom om satellitterminalens position på jordytan. Målsättningen är intressant då GNSS-operatörer (främst i det allmänna USA-drivna GPS-systemet men möjligen även i de tillkommande franska, kinesiska, ryska och europeiska systemen) begränsar den allmänna tillgängligheten av taktiska/strategiska skäl vid konflikter och kriser. Därtill att allmänna globala navigationssatellittjänster, GNSS-system, ofta bygger på mottagningsantenner med låg riktverkan vilka kan störas ut av lokala störningskällor. En mobil satellitterminal blir därmed beroende av manuell inmatning av riktningsvinklar för att upprätta nya satellitkommunikationslänkar. Systemet blir då mycket sårbart. I denna rapport återges resultat från mätserier inhämtade vid satellitterminalinstallationer utförda i Frankrike, Indonesien, Kanada, Polen, Sverige och USA. / The objective of the thesis is to evaluate a method for establishing a communication link from a mobile earth station to a geostationary communication satellite without prior knowledge of the position of the earth station. The objective is interesting as the GNSS-operators (mainly in the United States-run GPS-system, but possibly also in the French, Chinese, Russian and European systems) limits the general availability of tactical/strategic reasons during conflicts and crises. Furthermore, general GNSS-systems are based on receiving antennas with low directivity which can be disrupted by a local opponent or by other local sources of interference. A mobile earth station, lacking proper positioning information, depends on manual entry of directional angles to establish new satellite communication links. The system then becomes very vulnerable. This report evaluates measurement data gathered from deployed satellite terminal installations in Canada, France, Indonesia, Poland, Sweden and the U.S.

In this thesis, we present the design and implementation of a CubeSat receiver system using the Universal Software Radio Peripheral (USRP) and GNU Radio. The goal of this project is to develop a low-cost and flexible ground station capable of receiving telemetry and payload data from CubeSats in real time. The CubeSat receiver operates in the UHF frequency range with a center frequency of 435 MHz and uses a software-defined radio (SDR) approach to provide wideband signal processing and demodulation capabilities. The satellite transceiver transmits an Ax.25 Transciever packet every 1 second using the Pumpkin CubeSat kit programmed in MPLab. To achieve this goal, we discuss the design considerations for the receiver system, including the selection of suitable hardware components and the development of custom software blocks in GNU Radio. We also developed the GFSK-based transmitter and receiver in GNU Radio, as well as a tracking system for the satellite. To decode the Ax.25 radio packet transmitted by the Pumpkin CubeSat kit, we developed an Ax.25 deframer in GNU Radio to decode the received signal. Our results demonstrate that the CubeSat receiver is capable of receiving and demodulating AX.25 formatted radio signals from Transciever. Additionally, we show that the receiver system is scalable and can be easily adapted for use with other CubeSat missions. Overall, our work provides a practical solution for CubeSat communication and lays the groundwork for future developments in low-cost CubeSat ground station technology.

Satellites typically communicate with locations on the ground to receive commands and send data back. Establishing reliable communications generally requires dedicated ground stations, which in turn require hardware and expertise. Developers of nano-satellites, however, may not have the expertise or resources necessary for establishing a dedicated ground station. Therefore, the use of an existing communication system, such as the Satellite Personal Communication Networks (S-PCNs), is attractive. Another shortcoming of the fixed ground stations, already available, is that they are normally only able to communicate with Low Earth Orbit (LEO) nano-satellites four times per day (two10-minute windows separated by 90 minutes, followed 12 hours later by two more such 10-minute windows). This drawback is also overcome by the use of S-PCNs which provide increased access times, smaller gaps in contact between the satellites and ground stations, and easier tracking of satellite health. In this thesis, the capabilities of S-PCNs for communications with a nano-satellite are explored. Software simulation and analysis have been performed to assess system performance. Ground testing of the hardware is done to understand the use of such systems for small satellites.

Software-defined radio is a continuously developing technology applied in fields of mobile communications and among others. It is a radio communication system where software is used to implement parts of its functionality in an embedded system or computer. Devices which can transmit and receive different radio protocols based on software has major advantages. The ability to be able to reconfigure and change functionality on the fly to adapt to different environments is suited for multiple different applications, one of such is the environment in space. Distortions such as phase, frequency and timing offset all occur in such environment. The effects of these distortions can be reduced using different synchronization techniques in the receiver. A polyphase symbol timing synchronizer with two different timing error detectors, is designed in Simulink consisting of an 8-tap polyphase filter bank, a zero-crossing or Gardner timing error detector, a second order Phase-locked loop and a numerically controlled oscillator. The initial design uses floating-point precision. A fixed-point model is implemented using Xilinx System Generator and is used to generate a custom IP. Simulation is done by implementing a transceiver model with Simulink for the transmitter and parts of the receiver. The polyphase symbol timing synchronizer locks after about 4000 symbols for lower signal-to-noise and the Gardner timing error detector performs better than the zero-crossing error detector at higher signal-to-noise ratios.

Transportation across the globe's oceans increases every year and is expected to keep increasing in the following decades. Consequently, there is a need to establish communication over the horizon through the Automatic Identification System (AIS) and the Very High Frequency (VHF) Data Exchange System (VDES), still in development, to track and communicate with vessels all over the globe regardless of the distance from shore. In this Master thesis a feasibility study for the development of a system that fulfils that need is proposed consisting of a Low Earth Orbit (LEO) constellation providing VDES communication continuously all over the globe. A system engineering approach has been followed, identifying stakeholders and producing system requirements setting up a framework for the system. The key stakeholders were found to be the customers/users, the satellite provider, the satellite operator, the service provider and the payload provider. Furthermore, possible use-cases were presented and a system architecture was defined to outline the system, dividing the system into three segments: the space segment, the ground segment and the launch segment. In addition, design proposals for a satellite constellation and a typical satellite in such a constellation were implemented. The satellite constellation was proposed to consist of 91 satellites at an orbit altitude of around 550 km in polar orbits of common inclination, this was regarding a minimum elevation angle of 10 degrees. The satellite is recommended to consist of a 6 U CubeSat using as payload the existing airborne transponder R5A from Saab TransponderTech, it builds on the Software Defined Radio (SDR) technology and is to be further developed for VDES applications. Moreover, a link- and a data budget were implemented. Different launch options were addressed concluding that launching as secondary payload on a ride-share mission or as primary payload on a small satellite launch vehicle are the preferable options. A market analysis has been made providing details on how many AIS/VDES satellites that have been launched into LEO and by which service provider, as well as further details on small/nano satellites of extra interest to this work. A short risk evaluation was also done, identifying the most evident risks with developing, operating and disposing the system. In addition, Saab's potential role in the development of satellite VDES is discussed.  In conclusion to this work it has been shown that it is possible to build a global continuous satellite constellation in LEO utilising as payload an SDR-platform to provide VDES services to vessels at open seas. / Transport globalt till havs ökar varje år och förväntas fortsätta att öka de följande årtiondena. Följaktligen finns ett behov av att etablera över horisonten kommunikation genom det automatiska identifieringssystemet (AIS) och det väldigt högfrekventa datautbytessystemet (VDES), under utveckling, för att spåra och kommunicera med fartyg över hela världen oberoende av avståndet från land. I detta examensarbete har en förstudie utförts för utvecklingen av ett system som uppfyller detta behov. Systemet föreslås bestå av en låg jordbana satellitkonstellation som kontinuerligt tillhandahåller VDES-kommunikation över hela världen. Ett systemtekniskt tillvägagångssätt har följts, intressenter har identifierats och utifrån dessa har systemkrav tagits fram. De viktigaste intressenterna befanns vara användare/kunder, satellitleverantören, satellitoperatören, tjänsteleverantören och nyttolastleverantören. Vidare lyftes olika möjliga användningsområden för systemet fram och en systemarkitektur framställdes vari systemet delades in i tre segment: rymdsegmentet, marksegmentet och uppskjutningssegmentet. Dessutom genomfördes designförslag för en satellitkonstellation samt en typisk satellit i en sådan konstellation. Satellitkonstellationen föreslogs bestå av 91 satelliter på en altitud på omkring 550 km i polära banor med gemensam inklination, detta var gällande för en minimum elevationsvinkel på 10 grader. Satelliten rekommenderades bestå av en 6 U CubeSat med den befintliga luftburna transpondern R5A från Saab TransponderTech som nyttolast, vilken bygger på mjukvaruradioteknik och är tänkt att vidareutvecklas för VDES-applikationer.  Vidare, implementerades en länk- och data budget. Olika uppskjutningsmöjligheter undersöktes, varav slutsatsen att uppskjutning som sekundär nyttolast på ett delningsuppdrag eller som primär nyttolast medhjälp av ett mindre uppskjutningsfordon anpassat för små satelliter var de föredragna alternativen. Även en marknadsanalys har genomförts, där det redogjorts för hur många AIS / VDES - satelliter som har uppskjutits i LEO och av vilken tjänsteleverantör, samt ytterligare detaljer om små / nano satelliter av extra intresse för arbetet. En kort riskbedömning har också gjorts, där de mest uppenbara riskerna med utveckling, drift och undanröjande av systemet identifierats. Dessutom diskuteras Saabs möjliga roll i utvecklingen av satellit VDES. Slutsatsen av detta arbete har visat att det är möjligt att bygga en global kontinuerlig satellitkonstellation i låg jordbana med en mjukvaruradio som nyttolast som tillhandahåller VDES-tjänster till fartyg på öppna hav.