<p>Digital television is one of the biggest broadcasting media available. All over the world television companies are rearranging their broadcasting from analogue to digital transmission. Former standard disagreements in the analogue era have lead to an agreement of one common European standard for digital television. Countries like USA and Japan have their own similar standards.</p><p>The report consists of two objectives; a survey of the most commonly used standards for digital television today and the construction of a prototype receiver for the second generation satellite DVB-standard.</p><p>A thorough literature study and careful design resulted in a fully functioning system. Measurements performed on the DVB-S sections gave exemplary results. Comparing these results with corresponding measurements performed on the DVB-S2 section showed much better performance for DVB-S2 with the same code rates. This shows some of the advantages of the new standard and proving the coding theory right. New coding algorithms make it possible to transmit more information on noisier channels of inferior quality. In laymen’s words; DVB-S2 gives a better picture and more television channels on the same satellite compared to DVB-S.</p>

Σκοπός της συγγραφής της παρούσας διπλωματικής εργασίας είναι η μελέτη και ο σχεδιασμός της μονάδας συγχρονισμού φάσης σημάτων τεχνολογίας DVB-S2. Ο ρόλος της μονάδας αυτής είναι καθοριστικής σημασίας για την εξασφάλιση της αποδοτικής λειτουργίας των συστημάτων του προτύπου αυτού σε τυπικά δορυφορικά κανάλια. Αρχικά πραγματοποιείται μια εισαγωγή στις βασικές έννοιες και στη δομή ενός δορυφορικού συστήματος και εξετάζονται οι δυσμενείς επιδράσεις της ατμόσφαιρας κατά τη μετάδοση των δορυφορικών σημάτων. Ακολούθως γίνεται παρουσίαση της μετάδοσης τηλεοπτικών προγραμμάτων μέσω δορυφόρου και αναλύονται βασικά χαρακτηριστικά του δορυφορικού προτύπου DVB-S2. Παρουσιάζεται λεπτομερώς η αρχιτεκτονική μετάδοσής του και αξιολογείται η απόδοση του. Σημαντικό τμήμα της εργασίας αποτελεί η μελέτη του συγχρονισμού της παραμέτρου φάσης των λαμβανόμενων σημάτων σε δέκτες ψηφιακών συστημάτων επικοινωνίας. Αφού αναλυθεί η διαδικασία συγχρονισμού και τα χαρακτηριστικά της εκτίμησης της τιμής παραμέτρων των μεταδιδόμενων σημάτων, αναλύονται οι διατάξεις που υλοποιούν το συγχρονισμό φάσης σε σήματα τεχνολογίας DVB-S2 και εκτιμάται η απόδοσης λειτουργίας τους. Στη συνέχεια, περιγράφεται η διαδικασίας ανάπτυξης του μοντέλου υλοποίησης σε υλικό (FPGAs) της παραπάνω μονάδας, αξιοποιώντας το εργαλείο System Generator 10.1 της Xilinx και το περιβάλλον Simulink της Matlab. Τέλος, παρουσιάζεται και αναλύεται η ορθή λειτουργία της σχεδίασης για πραγματικά σήματα DVB-S2. / The purpose of this diploma thesis is the study and hardware implementation of Carrier Phase Recovery Unit for DVB-S2 systems. This operation of this unit of crucial importance complementing outstanding performance results over typical satellite channels. In the first part of this thesis, an introduction on important principles of satellite communications is carried out and the architecture of a satellite communication system is presented. Among others, the aggravating atmospheric effects taking place during satellite transmission are outlined. Afterwards, satellite transmission of television programs is examined and an analysis of the satellite standard DVB-S2 follows. The structural design of the transmission system is stated in detail and the efficiency of this standard is assessed. A substantial part of this work concerns the study of phase synchronization for digital communication receivers. After the theoretical analysis of the synchronization process, the unit implementing phase recovery for DVB-S2 systems is presented and its efficiency is examined for different kinds of distortions. Moreover, the procedure of hardware implementation (on FPGAs) of this unit is discussed, with the use of both Xilinx System Generator 10.1 and Simulink design tools. This thesis is concluded after presenting the efficient operation of the above implementation for real DVB-S2 signals.

Στην παρούσα διπλωματική εργασία παρουσιάζεται η υλοποίηση του συγχρονισμού ενός δορυφορικού δέκτη τεχνολογίας DVB-S2 με χρήση προϊόντων από την βιβλιοθήκη Xilinx του Simulink της Matllab. Αρχικά εξετάσαμε τη γενική συμπεριφορά ενός δέκτη και στη συνέχεια κατανοώντας τα ιδιαίτερα χαρακτηριστικά της τεχνολογίας DVB-S2, πραγματοποιήσαμε θεωρητική μελέτη του κυκλώματος που θα υλοποιήσουμε. Σαν επέκταση της παραπάνω μελέτης εξηγήσαμε δίνοντας παραδείγματα, για ποιους λόγους σε κάθε σημείο του συγχρονιστή επελέχθη το εκάστοτε υλισμικό-λογισμικό, από θεωρητικής άποψης. Έπειτα μας δόθηκε ένα μοντέλο, το οποίο ήταν υλοποιημένο με προϊόντα από την γενική βιβλιοθήκη (Simulink) της Matllab· στη συνέχεια δημιουργήσαμε ύστερα από διεξοδικά πειράματα και συγκρίσεις ένα μοντέλο, υλοποιημένο με προϊόντα από τη βιβλιοθήκη Xilinx του Simulink της Matllab, με συμπεριφορά ίδια με αυτή του μοντέλου που μας δόθηκε. Τέλος, παρουσιάσαμε μέσω γραφικών παραστάσεων και γραφημάτων τόσο τη σύγκριση της συμπεριφοράς των δυο μοντέλων, όσο και τη λειτουργία και τις ιδιαιτερότητες αυτού καθ’ εαυτού του μοντέλου που δημιουργήσαμε. / In this diplomatic work we present the concretization of timing of satellite receptor of technology DVB-S2 with use of products from the library Xilinx of Simulink of Matlab. Initially we examined the general behavior of receptor and afterwards comprehending the particular characteristics of technology DVB-S2, we realized theoretical study of circuit that we will materialize. As extension of previous study we explained giving examples, for what reasons we chose each hardware-software, from theoretical point of view. Then we were given a model, which was materialized with products from the general library (Simulink) of Matllab; afterwards we created after extensive experiments and comparisons, a model, materialized with products from the library Xilinx of Matllab Simulink, with behavior precisely same with that of model that was given to us. Finally, we presented via graphic representations and illustrations both the comparison of behavior of two models, and the operation and the particularities each one of the models we created.

William Henry Fox Talbot (1800-1877), the inventor of photography on paper, was given crucial support by his colleague Sir John Herschel (1792- 1871). Fellows of The Royal Society, the two men made fundamental contributions to optics, chemistry, light, and mathematics. Both were humanists of diverse interests and had strong role models in women. For Talbot, it was his mother, Lady Elisabeth Feilding. Herschel learned some of his earliest science from his Aunt, Caroline Herschel; his wife, Margaret, was an active participant in his work. During the pre-history of photography, Mrs. Fulhame, Thomas Wedgwood, Sir Humphry Davy, and Nicephore Niepce demonstrated its potential. The question is why, rather than how, was photography invented and announced in 1839? The camera and the chemistry necessary for the art's invention co-existed for many decades. Frustrated in trying to sketch with Wollaston's camera lucida, Talbot conceived of photography; Herschel avoided making photographs because he was an expert draughtsman adept with the camera lucida. Herschel, following inductive reasoning, made seminal contributions to the field of photochemistry; he invented the cyanotype process and was the first to apply hypo to fix photographs. Talbot learned from his own photographs and grew into being the first photographic artist. Talbot and his rival, Louis Daguerre, mirrored the competitive economic race and differences in support of science and art between France and Great Britain. By the Great Exhibition in 1851, Herschel and Talbot had been forcefully removed from work in photography. Herschel's health was broken in service as Master of the Mint. He remained an important influence on other photographers, including Anna Atkins, Charles Piazzi Smyth, and Julia Margaret Cameron. Talbot learned from experience in photographic book publishing that silver photographs could never be made permanent. He applied his efforts to perfecting photoglyphic engraving, a forerunner of photogravure; he also invented the photographic halftone.

No description available.

Cone cyclic nucleotide-gated (CNG) channels are located in the retinal outer segments, mediating daylight color vision. The channel is a tetramer of A-type (CNGA3) and B-type (CNGB3) subunits. CNGA3 subunits are able to form homotetrameric channels, but CNGB3 exhibits channel function only when co-expressed with CNGA3. Mutations in the genes encoding these cone CNG subunits are associated with achromatopsia, an autosomal recessive genetic disorder which causes incomplete or complete loss of daylight and color vision. A missense mutation, aspartatic acid (Asp) to asparagine (Asn) at position 262 in the canine CNGB3 subunit (cB3-D262N), results in loss of cone function and therefore daylight blindness, highlighting the crucial role of this aspartic acid residue for proper channel biogenesis and/or function. Asp 262 is located in a conserved region of the second transmembrane segment containing three Asp residues designated the Tri-Asp motif. We exploit the conservation of these residues in CNGA3 subunits to examine the motif using a combination of experimental and computational approaches. Mutations of these conserved Asp residues result in a loss of nucleotide-activated currents and mislocalization in heterologous expression. Co-expressing CNGB3 Tri-Asp mutants with wild type CNGA3 results in functional channels, however, their electrophysiological characterization matches the properties of homomeric CNGA3 tetramers. This failure to record heteromeric currents implies that Asp/Asn mutations impact negatively both CNGA3 and CNGB3 subunits. A homology model of canine CNGA3 relaxed in a membrane using molecular dynamics simulations suggests that the Tri-Asp motif is involved in non-specific salt bridge pairings with positive residues of S3 - S4. We propose that the CNGB3-D262N mutation in daylight blind dogs results in the loss of these interactions and leads to an alteration of the electrostatic equilibrium in the S1 - S4 bundle. Because residues analogous to Tri-Asp residues in the voltage-gated Shaker K+ channel superfamily were implicated in monomer folding, we hypothesize that destabilizing these electrostatic interactions might impair the monomer folding state in D262N mutant CNG channels during biogenesis. Another missesnse sense mutation, Arginine (Arg) to tryptophan (Trp) at position 424 in the canine CNGA3 subunit (cA3-R424W), also results in loss of cone function. An amino acid sequence alignment with Shaker K+ channel superfamily indicates that this R424 residue is located in the C-terminal end of the sixth transmembrane segment. A3-R424W mutant channels resulted in no cyclic nucleotide-activated currents and mislocalization with intracellular aggregates. However, the localization of cA3-R424W mutant channels was not affected as severely as the Asp/Asn mutation in S2 Tri-Asp motif, showing a lot of cells with the proper localization of Golgi-like and membrane fluorescence. Moreover, the substitution of Arg 424 to Lysine (Lys), conserving the positive charge, preserved channel function in some cells, which is different from the results of the S2 Tri-Asp motif in which the Asp/Glu substitutions, conserving the negative charge, leads to loss of cyclic nucleotide-activated currents. Even though these missense mutations are both associated with canine daylight blindness, the Arg 424 residue might not be as critical for folding as the Tri-Asp residues in the S2 Tri-Asp motif and might be more of a problem in channel structure and function. The cA3 model relaxed with MD simulations indicated a possible interaction of Arg 424 with the Glu 304 residue in the S4-S5 linker. This hypothesis is supported by electrophysiological data in which the double mutation of reversing these residues, Glu 306 to Arg and Arg 424 to Glu (E306R-R424E) preserves channel function. In the model, this salt bridge appears to contribute to stabilization of the open pore state. The R424W mutation might disrupt the salt bridge formation, leading to deforming and closing the pore region. / Biology

Complexes of the general formula M(X-SALDAPE) and M(X-SALDAPS) formed by the reaction of substituted salicylaldehydes and bis(3,3'-aminopropyl)ether or bis(3,3'-aminopropyl)sulfide with nickel(II) and cobalt(II) have been isolated. The complexes have been characterized by elemental analysis, mass spectra, infrared spectra, magnetic susceptibility measurements, and ultraviolet-visible-near infrared spectra. In the solid state the nickel(II) complexes, Ni(X-SALDAPE) and Ni(X-SALDAPS), where X = H, 5-Br, 3-(CH₃)₂CH, or 3-CH₃O, are speculated as pseudo-square planar or weak low-spin five-coordinate structures. The complexes exhibit anomalous magnetic behavior explained in terms of a spin state isomerism between singlet and triplet spin states. In a non-coordinating solvent, the nickel complexes are pseudo-square planar losing all five-coordinate structural features due to salvation. When dissolved in a coordinating solvent, the complexes are high-spin pseudo-octahedral. The cobalt(II) complexes, Co(H-SALDAPE) and Co(X-SALDAPS) where X = H, or 3-(CH₃)₂CH, were found to be high-spin pseudo-tetrahedral in the solid state with magnetic moments of approximately 3.4 B.M. The olive green nickel complexes are stable to air and moisture. The brownish cobalt complexes are stable as dry solids, but very easily oxidized when wet. / Master of Science

Les retours et les études dont on dispose sur les réseaux IP par satellite ne permettent pas d’apprécier les performances dont ils sont capables. Pourtant, les difficultés de transmettre de l’IP par satellite persistent encore. L’inadaptation du protocole IP, initialement conçu pour des réseaux terrestres, au large produit délai-bande du média satellite est une raison. Le fonctionnement souvent dé-corrélé entre les niveaux supérieurs de la pile TCP/IP et les couches physique et MAC du média satellite, est une autre. Dans le cadre de ce travail de thèse nous adoptons une démarche expérimentale basée sur l’observation, l’analyse et l’évaluation de systèmes implantant des technologies IP par satellite tels que le standard DVB-RCS, la technologie propriétaire iDirect ou la nouvelle norme DVB-S2. Nous étudions l’impact des règles de qualité de service IP sur les performances des applications dans un contexte de bande limitée. Nous nous penchons notamment sur l’évaluation des efficacités de l’encapsulation IP en termes de consommation de bande. Notre premier objectif est de déceler les niveaux auxquels un opérateur peut agir en vue d’optimiser la configuration d’un système IP par satellite et en accroître les performances / Despite of a number of IP satellite networks developed and deployed, only a limited number of studies and feedbacks about the performance is available. IP over satellite systems raises several constraints. One of the main reasons is the lack of adaptation of IP protocol, initially designed for terrestrial wired networks, to the large bandwidth delay product of the satellite media. Another reason is a lack of coordination between the IP protocol stack upper layer and the satellite MAC and physical layer. The purpose of this PhD study is to evaluate and assess the behaviour of IP applications when conveyed over satellite systems. We mainly focus on the IP quality of service performance, bandwidth encapsulation efficiency as well as IP applications metrics. Through the observation, we try to find how it’s possible to modify the IP satellite systems configuration in order to improve IP applications performance. We also suggest some ideas about the way to refine these technologies with regards to the design aspects. Experimentations have been performed over test beds implementing both standardised satellite technologies such as DVB-RCS as well as proprietary systems such as iDirect in addition to the new normalised technology DVB-S2

Nos travaux de thèse ont pour objectif la conception, la mise en Suvre et l'évaluation d'architectures pour la mobilité et la qualité de service (QoS) dans des systèmes satellites DVB-S2/RCS. Ces systèmes peuvent constituer une solution alternative efficace aux réseaux terrestres dans des zones reculées à faible densité de population mais ils doivent pour cela offrir les mêmes services tout en tenant compte de leurs caractéristiques spécifiques, en particulier leur long délai de transmission qui peut s'avérer problématique dans le cadre d'applications multimédias interactives. Notre première contribution a donc été de développer une architecture de QoS adaptée à ce type d'applications, utilisant le modèle DiffServ et se basant essentiellement sur l'interaction entre l'architecture liée au protocole d'initiation de session SIP et différentes entités du système satellite. La QoS peut alors être configurée de façon précise au niveau des STs, par le biais de l'outil TC, en analysant les descripteurs de session SDP compris dans les messages SIP et en déduisant leurs caractéristiques (débit, gigue max, délai max, etc...) soit localement si elles sont connues, soit à partir d'un service Web que nous avons développé. Nous avons ensuite proposé et développé une solution de mobilité basée sur SIP, adaptée au système satellite ainsi qu'à la solution de QoS précédemment décrite. Les performances de cette solution ont alors été comparées, en termes de temps d'interruption et de consommation de ressources, avec celles obtenues par Mobile IPv6 et certaines de ses extensions, démontrant ainsi de réelles améliorations pour le cas des applications multimédias interactives. Enfin, notre dernière contribution a été de développer deux architectures couplant QoS et mobilité, une spécifiquement conçue pour les applications interactives et basée sur la combinaison de notre solution de mobilité SIP avec notre architecture de QoS SIP et une autre basée sur Mobile IPv6 ou FMI Pv6 et sur l'interaction d'un QoS Agent mobile avec les entités de QoS du système satellite. Ces architectures ont été évaluées et comparées sur la plateforme d'émulation PLATINE développée dans le cadre du projet SATSIX.

Les télécommunications par satellite ont connu ces dernières années un regain d'intérêt important, du fait de leur capacité à permettre la réduction de la fracture numérique. En effet, un satellite en orbite géostationnaire peut s'appuyer sur une très grande couverture et une capacité importante pour atteindre des zones où le déploiement des réseaux terrestres n'est pas envisageable, comme les transports (bateau, avion), ou bien les zones blanches, où il serait difficilement rentable. Traditionnellement concentrés sur la diffusion de télévision numérique, les dernières générations de standards reflètent cet engouement en faisant une place de choix à la transmission de données bidirectionnelle, notamment en permettant une prise en charge simple des protocoles de l'Internet. Le problème de l'ordonnancement dans ces systèmes devient alors particulièrement important, puisqu'il doit prendre en compte deux processus évoluant de manière totalement décorrélée. D'un côté, l'évolution de la demande des utilisateurs, dépendante des applications (vidéo, voix, données). De l'autre, l'évolution de la capacité du système, celle-ci étant tributaire des conditions de transmission : les fréquences utilisées dans ces systèmes sont particulièrement sensibles à l'atténuation due à l'eau dans l'atmosphère. Cette thèse s'intéresse au problème de l'ordonnancement et de l'allocation de ressources, dans le but de fournir un service comparable aux réseaux terrestres en termes de services, en présentant les meilleures performances possibles. Si un certain nombre de propositions ont été faites sur le sujet, aucune ne prend en compte l'ensemble des contraintes d'un tel système. Outre le caractère variable de la capacité, la variabilité de la demande, conjuguée avec les contraintes de qualité de service constitue une difficulté supplémentaire. Enfin, il nous faut considérer la faisabilité de notre solution dans un contexte temps réel, nécessaire dans l'optique d'une implantation dans un système réel. Nous avons ainsi développé une architecture d'ordonnanceur pour la voie Aller, reposant sur des fonctions d'utilité, permettant ainsi une formulation simple du compromis entre demande et capacité. Nous montrons comment cet algorithme pourrait être utilisable dans un système complet, à travers une implantation détaillée, de faible complexité, ainsi que des simulations de cas réels. Nous portons ensuite notre attention sur la voie Retour, où nous proposons une méthode d'allocation de ressources prenant en compte de manière conjointe la qualité de service et la qualité du support pour délivrer une allocation à la fois conforme et performante. Les simulations montrent que notre algorithme obtient une efficacité et une meilleure gestion du trafic que des solutions de référence présentées dans la littérature. / Satellite telecommunications have seen a tremendous increase in interest, due to its ability to reduce the digital divide. In fact, a geostationary satellite can take advantage of its very wide coverage and high capacity to reach areas where deployment of a terrestrial network would not be possible, such as transports, or too expensive to be profitable, as in remote areas. Traditionally focused on digital television broadcasting, the latest generation of standards have evolved to reflect those new needs, dealing extensively with the transmission of interactive data, particularly by natively supporting Internet protocols. Scheduling has arisen as a major issue of those modern systems, since it has to deal with to highly uncorrelated processes: demand and capacity. Demand, on one side, evolves with user's needs, and therefore with the applications they are using: video, voice or data. Capacity, on the other side, depends on meteorological conditions over the satellite's cover, as the frequencies used in such systems are very sensitive to wet atmosphere attenuation. This thesis aims to study the problem of scheduling and resource allocation, hoping to achieve a service that can match with terrestrial networks in terms of services, while showing the best possible performances. If numerous solutions were proposed on this topic, none is taking into account all of the current system's constraints. In addition to the variable nature of system's capacity, the conjunction of variable demand and quality of service constraints constitutes an additional issue. Furthermore, we have to consider the practicability of our solution in a real-time context, necessary if we aim for industrial use. We have first developed a scheduler architecture for the Forward link, based on utility functions, thus allowing a simple formulation of the capacity versus demand compromise. We show, through a detailed low-complexity implementation and accurate simulations, how our algorithm could be used efficiently in an industrial context. We then focus on the Return link, where we propose a resource allocation method, taking into account quality of service and quality of transmission jointly to deliver an efficient yet consistent resource allocation. Simulations show that our algorithm achieves a better efficiency and traffic handling than reference solutions presented in the literature.