Satellite communication was operated exclusively in C-bandprior to 1970. Since then there has been an explosive growth in the demand for telecommunication services that are either only feasible via satellite or very cost effective by that means. This has prompted a steady growth in the utilization of higher frequencies in the Ku-band and above. The higher frequencies offer various advantages such as increased bandwidth, smaller antennas, and smaller satellite footprints that give higher EIRP permitting greater frequency reuse. The main drawback however is that they are subject to more severe propagation degradation. The small size antennas employed in VSAT and USAT systems significantly reduce the cost of earth station terminals and also eliminate tracking requirements, but they lose the mitigating effect of aperture averaging and hence experience stronger scintillation. The result is random fading and enhancement in the received signal amplitude, which will have a significant impact on the performance of low-margin communication systems operating at high frequencies (> ~10GHz) and low elevation angles, and utilising small antennas. Scintillation effects need to be considered in the design and link-budget calculations of these systems. In this thesis, the results are shown of an extensive measurement analysis of tropospheric scintillation, using the ITALSATsatellite beacon signals at 18.7, 39.6 and 49.5 GHz, recorded at Sparsholt, U.K., at an elevation angle of 29.9°. The analysis was carried out in order to study the effects of scintillation due to tropospheric turbulence and their impact on satellite digital communication systems. The first part of the thesis deals with the preprocessing of raw propagation data and presents various statistical results relating to the stationary aspects of the scintillations, i. e. pdf of amplitude and intensity; long and short term statistics of amplitude scintillation distributions. The relationship of scintillation with link parameters and meteorological parameters are also studied. The second part of the thesis investigates the dynamic characteristics of scintillation. It examines the observed effects of wind and cloud presence on the intensity and power spectrum of tropospheric scintillation and then moves on to present results relating to the analysis of the instantaneous frequency scaling of scintillation. In the third part of the thesis scintillation fade and enhancement duration statistics are presented for various threshold signal levels, and their use in fade countermeasures is examined. Finally, a study of adaptive fade countermeasures (FCM) that could be used for systems operating at Ka-band and above for mitigating the effects of scintillations and rain attenuation is presented. The last part, presents an improved global prediction model for both the long-term standard deviation and the signal level distribution of tropospheric scintillation. The model is validated using measurement results from satellite links in Europe, the United Sates and Japan at frequencies from 11 GHz to 50 GHz, and path elevation angles 5.8° to 40°.

As we move towards the sixth generation (6G) of connectivity, satellites have been identified as an indispensable solution to bridge the digital divide. The satellites offer an extensive coverage footprint and can reach the most remote regions with high throughput, fueled by the large bandwidth available in higher frequency bands. As the low earth orbit (LEO) satellites are closer to the earth and therefore have lower latency, we could use a mega-constellation of LEO satellites to complement the terrestrial networks in 6G. However, the satellite and terrestrial networks may compete for the same spectrum band, thereby being a source of interference for each other. The mmWave bands have attracted the attention of LEO satellite networks and terrestrial mobile operators alike. Specifically, the 28-GHz mmWave band (27.5-29.5 GHz) is licensed to Fixed Satellite Services (FSS) for earth-to-satellite uplink transmissions, while the terrestrial networks will use it for downlink operation. The satellite networks are the primary users of the 28 GHz band, while it is also available for licensing to International Mobile Telecommunication (IMT) networks. In some countries, the 28 GHz band is also used for point-to-multipoint (PMP) wireless backhaul links. Therefore, in this work, we aim to understand the impact of the earth station uplink transmissions on the terrestrial users, viz., the cellular users, and the backhaul points, and suggest methods to facilitate the coexistence of these networks in the 28 GHz band through exclusion zones. The average data rate of the networks is derived through stochastic geometry, which results in expressions that are not closed-form. To optimize the data rates of the coexisting networks jointly, we first approximate the coverage probability expressions as closed-form sigmoid curves. This enables us to use gradient descent methods to determine the optimal radii of the exclusion zones.

To compensate the strong Troposheric impairments caused in the Ka frequency band, it is necessary to use Fade Mitigation Techniques. To develop and validate such techniques, time series of rain attenuation are needed. Nevertheless, these data are difficult to obtain. An alternative to using real rain attenuation time series is to develop a model of rain rate time series synthesizer. Nevertheless, real rain rate time series are needed to develop and validate this model. The aim of this internship is to provide real rain rate data useful for the development, parameterization and validation of this new model. In the first part of this report, different rain rate computation methods will be presented. Then, real data from a rain gauge located at Onera premises in Toulouse will be processed according to the presented methods and to a novel one. Results will be statistically analysed and finally a study of both the error of the methods and the uncertainty of the experimental devices and tools will be carried out. / <p>Validerat; 20120514 (anonymous)</p>

In recent years, there has been an exponential growth in the use of multimedia applications. A satellite system offers great potential for multimedia applications with its ability to broadcast and multicast a large amount of data over a very large area as compared to a terrestrial system. However, the limited transmission capacity along with the dynamically varying channel conditions impedes the delivery of good quality multimedia service in a satellite system which has resulted in research efforts for deriving efficient radio resource management techniques. This issue is addressed in this thesis, where the main emphasis is to design a CAC framework which maximizes the utilization of the scarce radio resources available in the satellite and at the same time increases the performance of the system for a UMTS based satellite system supporting unicast and multicast traffic. The design of the system architecture for a UMTS based satellite system is presented. Based on this architecture, a CAC framework is designed consisting of three different functionalities: the admission control procedure, the retune procedure and the pre-emption procedure. The joint use of these functionalities is proposed to allow the performance of the system to be maintained under congestion. Different algorithms are proposed for different functionalities; an adaptive admission control algorithm, a greedy retune algorithm and three pre-emption algorithms (Greedy, SubSetSum, and Fuzzy). A MATLAB simulation model is developed to study the performance of the proposed CAC framework. A GUI is created to provide the user with the flexibility to configure the system settings before starting a simulation. The configuration settings allow the system to be analysed under different conditions. The performance of the system is measured under different simulation settings such as enabling and disabling of the two functionalities of the CAC framework; retune procedure and the pre-emption procedure. The simulation results indicate the CAC framework as a whole with all the functionalities performs better than the other simulation settings.

This thesis investigates the modelling of fade countermeasures (FCMs) for the design of geostationary Ka band digital satellite communication systems. The analysis focuses on a typical low-power low-rate very small aperture terminal application using adaptive forward error correction as a way of counteracting the high level of detected dynamic atmospheric fading. The management and performance of such systems is conditioned greatly by the ability of practical controllers at detecting the actual level of total signal attenuation. At 20 or 30 GHz, rain attenuation and tropospheric scintillation are the two major propagation effects of interest. Part of the solution relies on the consideration and integration of their random and dynamic nature in the design process. The finite response time of practical countermeasure systems is a source of performance degradation which can be minimised by the implementation of predictive control strategies. This is the focal point of this thesis. A novel on-line short-term predictor matched to the Ka band fading process is proposed. While the rain attenuation component is efficiently predicted, tropospheric scintillation is the source of the estimation error. To take this into account, a statistical model, based on an extension of the global fading model for rain and scintillation, is then developed so that long term performance of predictive countermeasures can be drawn. Two possible ways to compensate for scintillation-induced prediction errors, namely the fixed and variable detection margin approaches, are proposed, analysed and then compared. This is achieved by calculating the FCM utilisation factor, as well as the throughput and bit error rate performance of a typical Ka band system in the presence of dynamic fading within the context of predictive fade countermeasure control operations. In the last part of this thesis, the inclusion of instantaneous frequency scaling in the design of efficient FCM control schemes is investigated. This is applicable to systems using fade detection at a base frequency. In particular, a new statistical model, accounting for the impact of the stochastic temporal variations of rain drop size distribution on rain attenuation, is presented. This thesis further confirms that countermeasure systems are technologically viable. The consideration of more specific design problems does not change the overall validity of this statement. In this thesis, it is shown that a predictive FCM technique, based on readily available punctured convolutional codes, with their relatively modest coding gain, is sufficient to provide high link availability and user data throughput on a low-power low-rate in-bound VSAT link.

As the communication deficit in the Arctic region is enormous especially above 75 [Deg] N latitude, the concern and opportunity of providing reliable &amp; efficient connectivity in the Arctic region has beenduly noted &amp; understood by N66 Connect AB (N66). This case study documents a comprehensive research which implements system engineering approach for establishment of a Ground Station (GS) at Svalbard, Norway with sole focus of connecting the inaccessible geographical region lying in the Arctic with rest of the world. Several GS system &amp; subsystem are studied and comparative analysis is made on how the communication can be established with the N66 Connect AB (N66)’s potential clients and its satellites that are to be deployed in September, 2018.The case study resulted in analysis of several risks involved during development &amp; operation of the GS,the hardware, software &amp; operational architecture, the features of GS’s system capable of meeting N66’s objectives and the market potential of the service after GS operations.

京都大学 / 0048 / 新制・課程博士 / 博士(情報学) / 甲第22585号 / 情博第722号 / 新制||情||124(附属図書館) / 京都大学大学院情報学研究科数理工学専攻 / (主査)教授 梅野 健, 教授 山下 信雄, 教授 守倉 正博 / 学位規則第4条第1項該当 / Doctor of Informatics / Kyoto University / DFAM

This diploma thesis provides an overview and basic principles of satellite communication systems. Further is description of specific aerial satellite communication system ARINC 791. The practical part includes proposals of the system for automated verification targeting functionality of an air satellite antenna, which has been carried out in Honeywell laboratory conditions. The selected implementation is realized and used for automated verification targeting functionality of an air satellite antenna. The results are graphically evaluated.

In recent years, there has been an exponential growth in the use of multimedia applications. A satellite system offers great potential for multimedia applications with its ability to broadcast and multicast a large amount of data over a very large area as compared to a terrestrial system. However, the limited transmission capacity along with the dynamically varying channel conditions impedes the delivery of good quality multimedia service in a satellite system which has resulted in research efforts for deriving efficient radio resource management techniques. This issue is addressed in this thesis, where the main emphasis is to design a CAC framework which maximizes the utilization of the scarce radio resources available in the satellite and at the same time increases the performance of the system for a UMTS based satellite system supporting unicast and multicast traffic. The design of the system architecture for a UMTS based satellite system is presented. Based on this architecture, a CAC framework is designed consisting of three different functionalities: the admission control procedure, the retune procedure and the pre-emption procedure. The joint use of these functionalities is proposed to allow the performance of the system to be maintained under congestion. Different algorithms are proposed for different functionalities; an adaptive admission control algorithm, a greedy retune algorithm and three pre-emption algorithms (Greedy, SubSetSum, and Fuzzy). A MATLAB simulation model is developed to study the performance of the proposed CAC framework. A GUI is created to provide the user with the flexibility to configure the system settings before starting a simulation. The configuration settings allow the system to be analysed under different conditions. The performance of the system is measured under different simulation settings such as enabling and disabling of the two functionalities of the CAC framework; retune procedure and the pre-emption procedure. The simulation results indicate the CAC framework as a whole with all the functionalities performs better than the other simulation settings.

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