No / In the future mobile network, satellites will operate alongside cellular networks in order to provide seamless connectivity irrespective of the location of the user. Such a service scenario requires that the next generation of mobility management (MM) procedures are able to ensure terminal and user mobility on a global scale. This paper considers how the principles of Mobile-IP can be used to develop MM procedures for a heterogeneous access network, comprizing of satellite and cellular elements, connected to an IP core network.Initially, the system architecture is described. This is followed by a discussion of issues related to MM, where location, address and handover management are considered. A description of the signaling protocols for macro-mobility using Mobile-IP is then presented, emphasizing the need to minimize the change to the existing access network procedures. Finally, the performance of the protocols is analyzed in terms of the additional signaling time required for registration and handover.

International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California / Over a dozen commercial remote sensing programs are currently under development representing billions of dollars of potential investment. While technological advances have dramatically decreased the cost of building and launching these satellites, the cost and complexity of accessing their data for commercial use are still prohibitively high. This paper describes Reconfigurable Gateway Systems which provide, to a broad spectrum of existing and new data users, affordable telemetry data acquisition, processing and distribution for real-time remotely sensed data at rates up to 300 Mbps. These Gateway Systems are based upon reconfigurable computing, multiprocessing, and process automation technologies to meet a broad range of satellite communications and data processing applications. Their flexible architecture easily accommodates future enhancements for decompression, decryption, digital signal processing and image / SAR data processing.

In remote areas without conventional cellular service, satellite communication is often the only viable option. Handheld devices for use with satellite communication networks require a high transmit power to obtain a reliable signal. The need for a high transmit power makes it difficult for the device to meet specific absorption rate (SAR) restrictions. An adaptive beam forming technique for shaping radiation away from the user’s head is proposed. This technique uses a back-to-back patch antenna design with an impedance monitoring based system capable of adaptively controlling the pattern of the antenna. The adaptive antenna system was designed, simulated, fabricated, and measured. The system could detect a head phantom within 3 cm of the antenna. SAR levels were verified to be within safety restrictions at 3 cm through simulation. By turning off the patch facing the user’s head when the phone is transmitting, and the user’s head is within 3 cm, it was shown that SAR levels could be reduced to safe levels. / February 2017

L’objectif de la thèse est l’étude des codes correcteurs d’erreurs au niveau applicatif (Application Layer – Forward Error Correction, ou AL-FEC) pour les communications par satellite. Dans ce contexte, pendant les deux première années de thèse, nous avons proposé de nouvelles méthodes d’analyse, de construction et d’optimisation des codes à effacements définis par des matrices de parité à faible densité (code LDPC, pour « Low Density Parity Check » en anglais). La troisième année de la thèse a été consacrée à : (1) La suite des études portant sur de nouvelles méthodes de construction des codes LDPC non-binaires. D’une part, nous avons développé un nouvel algorithme (Scheduled-PEG) qui permet d’optimiser la construction des codes LDPC non-binaires pas rapport aux métriques de performance spécifiques à la couche application, notamment dans le cadre des systèmes de diffusion de contenu (broadcasting). D’autre part, nous avons proposé une nouvelle méthode de construction de codes à faible rendement, qui utilise l’image binaire étendue d’un code LDPC non-binaire. Ces études ont fait l’objet de deux publications dans deux conférences internationales : (a) “Scheduled-PEG construction of LDPC codes for Upper-Layer FEC”, International Workshop on Coding and Cryptography, April 2011, Paris, France. (b) “Extended Non-Binary Low-Density Parity-Check Codes over Erase Channels”, IEEE International Symposium on Wireless Communication Systems, November 2011, Aachen, Germany. (2) Une étude portant sur l’analyse asymptotique de codes cluster-LDPC non-binaires. Cette nouvelle classe de codes – introduite récemment (ISIT’2011) – se distingue par ses excellentes propriétés en termes de distance minimale. Notre étude a permis de déterminer de manière analytique la capacité de correction des codes cluster-LDPC non-binaires, aussi bien pour le décodage itératif par propagation de croyances (BP, pour « Belief Propagation ») que pour le décodage par maximum de vraisemblance (ML, pour « Maximum Likelihood »). Ces résultats seront intégrés à une publication scientifique sur les codes cluster-LDPC, en cours de rédaction, qui sera soumise à « IEEE Transactions on Information Theory », avant la fin de l’année 2011. (3) Une étude portant sur une méthode de construction des codes LDPC qui permet de réduire de manière significative le plancher d’erreur (« error floor ») du code, sans dégrader ses performances dans la région de « waterfall ». Ainsi, nous avons proposé la structuration de la matrice de parité du code, de manière à intégrer une partie irrégulière, optimisée pour la partie « waterfall », et une partie régulière, qui permet de réduire le plancher d’erreur du code. Cette étude fera l’objet d’une publication dans une conférence internationale (à déterminer), à soumettre début 2012. / The advent of content distribution, IPTV, video-on-demand and other similar services accelerate the demand for reliable data transmission over highly heterogeneous networks and toward terminals potentially heterogeneous too. In this context, Forward Error Correction (FEC) codes that operate at the transport or the Application Layer (AL-FEC) are used in conjunction with the FEC codes implemented at the physical layer, in order to improve the overall performance of the communication system. AL-FEC codes are aimed at recovering erased data packets and they are essential in many multicast/broadcast environments, no matter the way the information is transported, for instance using a wired or wireless link, and a terrestrial, satellite-based or hybrid infrastructure.This thesis addresses the design of Low Density Parity Check (LDPC) codes for AL-FEC applications. One the one hand, we provide an asymptotical analysis of non-binary LDPC codes over erasure channels, as well as waterfall and error-floor optimization techniques for finite-length codes. On the other hand, new concepts and coding techniques are developed in order to fully exploit the potential of non-binary LDPC codes.The first contribution of this thesis consists of the analysis and optimization of two new ensembles of LDPC codes. First, we have derived the density evolution equations for a very general ensemble of non-binary LDPC codes with rank-deficient coefficients. This allows improving the code performance, as well as designing ensembles of LDPC codes that can be punctured in an effective manner. The second approach allows the asymptotical optimization of a particular ensemble of LDPC codes, while ensuring low error-floors at finite lengths.The second contribution is the construction of finite length LDPC codes with good waterfall and error floor performance. Two approaches were investigated, according to the metric used to evaluate the code. The “Scheduled” Progressive Edge Growth (SPEG) algorithm is proposed, in order to optimize the waterfall performance of the code. Another method is proposed which consists in optimizing a specific structure of the parity check matrix. This approach gives low error-floors.The third contribution investigates a new technique of rate adaptability for non-binary LDPC codes. We propose a new method to generate “on-the-fly” incremental redundancy, which allows designing codes with flexible coding rates, in order to cope with severe channel conditions or to enable Fountain-like distribution applications.The fourth contribution focuses on a new class of LDPC codes, called non-binary cluster-LDPC codes. We derive exact equations of the density evolution for the iterative decoding and an upper bound for the maximum-likelihood decoding.Finally, we propose a practical solution to the problem of reliable communication via satellite to high-speed trains. Here, the challenge is that obstacles present along the track regularly interrupt the communication. Our solution offers optimal performance with a minimum amount of redundancy.

<p>The next generation satellite communication networks will provide multimedia services supporting high bit rate, mobility, ATM, and TCP/IP. In these cases, the satellite technology will act as the internetwork infrastructure of future global systems and assuming a global wireless system, no distinctions will exist between terrestrial and satellite communications systems, as well as between fixed and 3G mobile networks. In order for satellites to be successful, they must handle bursty traffic from users and provide services compatible with existing ISDN infrastructure, narrowcasting/multicasting services not offered by terrestrial ISDN, TCP/IP-compatible services for data applications, and point-to-point or point-to-multipoint on-demand compressed video services. This calls for onboard processing payloads capable of frequency multiplexing and demultiplexing and interference suppression.</p><p>This thesis introduces a new class of oversampled complex modulated filter banks capable of providing frequency multiplexing and demultiplexing. Under certain system constraints, the system can handle all possible shifts of different user signals and provide variable bandwidths to users. Furthermore, the aliasing signals are attenuated by the stopband attenuation of the channel filter thus ensuring the approximation of the perfect reconstruction property as close as desired. Study of the system efficient implementation and its mathematical representation shows that the proposed system has superiority over the existing approaches for Bentpipe payloads from the flexibility, complexity, and perfect reconstruction points of view. The system is analyzed in both SISO and MIMO cases. For the MIMO case, two different scenarios for frequency multiplexing and demultiplexing are discussed.</p><p>To verify the results of the mathematical analysis, simulation results for SISO, two scenarios of MIMO, and effects of the finite word length on the system performance are illustrated. Simulation results show that the system can perform frequency multiplexing and demultiplexing and the stopband attenuation of the prototype filter controls the aliasing signals since the filter coefficients resolution plays the major role on the system performance. Hence, the system can approximate perfect reconstruction property by proper choice of resolution.</p>

The next generation satellite communication networks will provide multimedia services supporting high bit rate, mobility, ATM, and TCP/IP. In these cases, the satellite technology will act as the internetwork infrastructure of future global systems and assuming a global wireless system, no distinctions will exist between terrestrial and satellite communications systems, as well as between fixed and 3G mobile networks. In order for satellites to be successful, they must handle bursty traffic from users and provide services compatible with existing ISDN infrastructure, narrowcasting/multicasting services not offered by terrestrial ISDN, TCP/IP-compatible services for data applications, and point-to-point or point-to-multipoint on-demand compressed video services. This calls for onboard processing payloads capable of frequency multiplexing and demultiplexing and interference suppression. This thesis introduces a new class of oversampled complex modulated filter banks capable of providing frequency multiplexing and demultiplexing. Under certain system constraints, the system can handle all possible shifts of different user signals and provide variable bandwidths to users. Furthermore, the aliasing signals are attenuated by the stopband attenuation of the channel filter thus ensuring the approximation of the perfect reconstruction property as close as desired. Study of the system efficient implementation and its mathematical representation shows that the proposed system has superiority over the existing approaches for Bentpipe payloads from the flexibility, complexity, and perfect reconstruction points of view. The system is analyzed in both SISO and MIMO cases. For the MIMO case, two different scenarios for frequency multiplexing and demultiplexing are discussed. To verify the results of the mathematical analysis, simulation results for SISO, two scenarios of MIMO, and effects of the finite word length on the system performance are illustrated. Simulation results show that the system can perform frequency multiplexing and demultiplexing and the stopband attenuation of the prototype filter controls the aliasing signals since the filter coefficients resolution plays the major role on the system performance. Hence, the system can approximate perfect reconstruction property by proper choice of resolution.

Σκοπός της διπλωματικής εργασία είναι η μελέτη και μοντελοποίηση ενός δορυφορικού καναλιού. Το δορυφορικό κανάλι, όπως κάθε κανάλι είναι ένα μη-γραμμικό σύστημα που χαρακτηρίζεται από ποικίλους και απρόβλεπτους παράγοντες που αλλοιώνουν την αρχική πληροφορία. Οι καιρικές συνθήκες που επικρατούν σε μια περιοχή για παράδειγμα επηρεάζουν το κανάλι προκαλώντας μεταβολή της ισχύος με τυχαίο τρόπο, γεγονός το οποίο δυσκολεύει την πρόβλεψη της συμπεριφοράς του. Για το λόγο αυτό έγινε προσπάθεια ανάπτυξης ενός δυναμικού μοντέλου που θα μπορεί να εξομοιώνει τη συμπεριφορά ενός τέτοιου καναλιού, δίνοντας τις πιθανές καταστάσεις στις οποίες μπορεί να βρεθεί. Συγκεκριμένα τα φαινόμενα τα οποία μελετήθηκαν είναι η εξασθένιση λόγω βροχής, η απορρόφηση από υγρασία και οξυγόνο και η τροποσφαιρική σκέδαση. Η κατασκευή του μοντέλου έγινε με τη χρήση και επεξεργασία μετεωρολογικών δεδομένων από την Ε.Μ.Υ. Επίσης, έγινε προσπάθεια μοντελοποίησης του ενισχυτή ισχύος (TWTA) ο οποίος συναντάται τόσο στο δορυφόρο όσο και κεντρικό σταθμό βάσης στη γη. / The objective of this project is the study and the modeling of a satellite channel. The satellite channel, as any satellite channel, is a non-linear system that is characterized by multiple and unpredictable factors that alter the initial information. The weather conditions that exist in an region affect the channel causing random power fluctuations and result in unpredictable performance. Thus, a dynamic model has been developed that simulates the performance of such a channel by predicting possible conditions that can arise. More specifically, the phenomena that have been studied is the rain attenuation, gaseous absorption and the tropospheric scintillation. The model was implemented through the use and analysis of meteorological data taken from the Hellenic National Meteorological Service. In addition, a high power amplifier (TWTA) that can be found both in the satellite and the central base station.

The CanX-4 and CanX-5 mission currently under development at The University of Toronto Institute for Aerospace Studies Space Flight Laboratory UTIAS/SFL is a challenging formation flying technology demonstration. Its requirements of sub-metre control accuracy have yet to be realized with nanosatellites. Many large technical challenges must be addressed in order to ensure the success of the CanX-4/5 mission. This includes the development of software for an intersatellite communication system, integration and optimization of key formation flying algorithms onto the Payload On-Board Computer as well as the development of a Hardware-In-The-Loop simulator for full on-orbit mission simulations. This thesis will provide background knowledge of the Space Flight Laboratory and its activities, the CanX-4/5 mission, and nally highlight the authors contributions to overcoming each of these technical challenges and ensuring the success of the CanX-4 and CanX-5 mission.

The CanX-4 and CanX-5 mission currently under development at The University of Toronto Institute for Aerospace Studies Space Flight Laboratory UTIAS/SFL is a challenging formation flying technology demonstration. Its requirements of sub-metre control accuracy have yet to be realized with nanosatellites. Many large technical challenges must be addressed in order to ensure the success of the CanX-4/5 mission. This includes the development of software for an intersatellite communication system, integration and optimization of key formation flying algorithms onto the Payload On-Board Computer as well as the development of a Hardware-In-The-Loop simulator for full on-orbit mission simulations. This thesis will provide background knowledge of the Space Flight Laboratory and its activities, the CanX-4/5 mission, and nally highlight the authors contributions to overcoming each of these technical challenges and ensuring the success of the CanX-4 and CanX-5 mission.

Thesis (M.S. in Systems Technology (Scientific and Technical Intelligence)) Naval Postgraduate School, Sept. 1995. / Thesis advisor(,):Peter Lavoy, Vicente Garcia. "September 1995" Includes bibliographical references (p. 81-82). Also available online.