Chaos theory is well known as one of three revolutions in physical sciences in 20th-century, as one physicist called it: Relativity eliminated the Newtonian illusion of absolute space and time; quantum theory eliminated the Newtonian dream of a controllable measurable process; and chaos eliminates the Laplacian fantasy of deterministic predictability". Specially, when chaos synchronization was found in 1991, chaos theory becomes more and more attractive. Chaos has been widely applied to many scientific disciplines: mathematics, programming, microbiology, biology, computer science, economics, engineering, finance, philosophy, physics, politics, population dynamics, psychology, and robotics. One of most important engineering applications is secure communication because of the properties of random behaviours and sensitivity to initial conditions of chaos systems. Noise-like dynamical behaviours can be used to mask the original information in symmetric cryptography. Sensitivity to initial conditions and unpredictability make chaotic systems very suitable to construct one-way function in public-key cryptography. In chaos-based secure communication schemes, information signals are masked or modulated (encrypted) by chaotic signals at the transmitter and the resulting encrypted signals are sent to the corresponding receiver across a public channel (unsafe channel). Perfect chaos synchronization is usually expected to recover the original information signals. In other words, the recovery of the information signals requires the receiver's own copy of the chaotic signals which are synchronized with the transmitter ones. Thus, chaos synchronization is the key technique throughout this whole process. Due to the difficulties of generating and synchronizing chaotic systems and the limit of digital computer precision, there exist many challenges in chaos-based secure communication. In this thesis, we try to solve chaos generation and chaos synchronization problems. Starting from designing chaotic and hyperchaotic system by first-order delay differential equation, we present a family of novel cell attractors with multiple positive Lyapunov exponents. Compared with previously reported hyperchaos systems with complex mathematic structure (more than 3 dimensions), our system is relatively simple while its dynamical behaviours are very complicated. We present a systemic parameter control method to adjust the number of positive Lyapunov exponents, which is an index of chaos degree. Furthermore, we develop a delay feedback controller and apply it to Chen system to generate multi-scroll attractors. It can be generalized to Chua system, Lorenz system, Jerk equation, etc. Since chaos synchronization is the critical technique in chaos-based secure communication, we present corresponding impulsive synchronization criteria to guarantee that the receiver can generate the same chaotic signals at the receiver when time delay and uncertainty emerge in the transmission process. Aiming at the weakness of general impulsive synchronization scheme, i.e., there always exists an upper boundary to limit impulsive intervals during the synchronization process, we design a novel synchronization scheme, intermittent impulsive synchronization scheme (IISS). IISS can not only be flexibly applied to the scenario where the control window is restricted but also improve the security of chaos-based secure communication via reducing the control window width and decreasing the redundancy of synchronization signals. Finally, we propose chaos-based public-key cryptography algorithms which can be used to encrypt synchronization signals and guarantee their security across the public channel.

Chaos theory is well known as one of three revolutions in physical sciences in 20th-century, as one physicist called it: Relativity eliminated the Newtonian illusion of absolute space and time; quantum theory eliminated the Newtonian dream of a controllable measurable process; and chaos eliminates the Laplacian fantasy of deterministic predictability". Specially, when chaos synchronization was found in 1991, chaos theory becomes more and more attractive. Chaos has been widely applied to many scientific disciplines: mathematics, programming, microbiology, biology, computer science, economics, engineering, finance, philosophy, physics, politics, population dynamics, psychology, and robotics. One of most important engineering applications is secure communication because of the properties of random behaviours and sensitivity to initial conditions of chaos systems. Noise-like dynamical behaviours can be used to mask the original information in symmetric cryptography. Sensitivity to initial conditions and unpredictability make chaotic systems very suitable to construct one-way function in public-key cryptography. In chaos-based secure communication schemes, information signals are masked or modulated (encrypted) by chaotic signals at the transmitter and the resulting encrypted signals are sent to the corresponding receiver across a public channel (unsafe channel). Perfect chaos synchronization is usually expected to recover the original information signals. In other words, the recovery of the information signals requires the receiver's own copy of the chaotic signals which are synchronized with the transmitter ones. Thus, chaos synchronization is the key technique throughout this whole process. Due to the difficulties of generating and synchronizing chaotic systems and the limit of digital computer precision, there exist many challenges in chaos-based secure communication. In this thesis, we try to solve chaos generation and chaos synchronization problems. Starting from designing chaotic and hyperchaotic system by first-order delay differential equation, we present a family of novel cell attractors with multiple positive Lyapunov exponents. Compared with previously reported hyperchaos systems with complex mathematic structure (more than 3 dimensions), our system is relatively simple while its dynamical behaviours are very complicated. We present a systemic parameter control method to adjust the number of positive Lyapunov exponents, which is an index of chaos degree. Furthermore, we develop a delay feedback controller and apply it to Chen system to generate multi-scroll attractors. It can be generalized to Chua system, Lorenz system, Jerk equation, etc. Since chaos synchronization is the critical technique in chaos-based secure communication, we present corresponding impulsive synchronization criteria to guarantee that the receiver can generate the same chaotic signals at the receiver when time delay and uncertainty emerge in the transmission process. Aiming at the weakness of general impulsive synchronization scheme, i.e., there always exists an upper boundary to limit impulsive intervals during the synchronization process, we design a novel synchronization scheme, intermittent impulsive synchronization scheme (IISS). IISS can not only be flexibly applied to the scenario where the control window is restricted but also improve the security of chaos-based secure communication via reducing the control window width and decreasing the redundancy of synchronization signals. Finally, we propose chaos-based public-key cryptography algorithms which can be used to encrypt synchronization signals and guarantee their security across the public channel.

[pt] O presente texto aborda aspectos do problema de sincronização em sistemas de telecomunicações, com enfoque nas funções de demodulação síncrona, regeneração, multiplexação/demultiplexação (TDM) e comutação (digital). São tratados os métodos de obtenção de referência de portadora e de referência de relógio, os recursos de malha de amarração de fase (PLL) e de memória elástica. O objetivo final consiste na descrição dos métodos de sincronização de rede, nas modalidades plesiócrona (e plesiócrona com justificação), mestre-escravo e sincronização mútua. As subredes de sincronização são analisadas em termos de topologia, segurança, determinação de freqüência e fases de operação e de compensação de defasagens na transmissão. A apresentação é feita em termos de um texto didático para a descrição dos problemas e de suas soluções. / [en] This text deals with aspects of synchronization in telecommunication systems, with emphasis on the operational functions of synchronous demodulation, signal regeneration, multiplexing/demultiplexing (TDM) and digital switching. The methods of carrier recovery, clock recovery, phase locked loop and elastic store are presented. The final goal consists on the description of network synchronization methods, in the plesiochronous (and plesiochronous with justification), master-slave and mutual synchronization modalities. The synchronization subnetworks are analised in terms of topology, safety, operation frequency and phases, and transmission phase delay compensation. The presentation is made in a didactical way, describing the problems and their possible solutions.

Le Cloud computing émerge comme le nouveau paradigme informatique dans lequel la virtualisation des ressources fournit des services fiables correspondant aux demandes des utilisateurs. De nos jours, la plupart des applications interactives et utilisant beaucoup de données sont développées sur le cloud: Le jeu vidéo en est un exemple. Avec l'arrivée du cloud computing, l'accessibilité et l'ubiquité du jeu ont un brillant avenir; Les jeux peuvent être hébergés dans un serveur centralisé et accessibles via l'Internet par un client léger sur une grande variété de dispositifs avec des capacités modestes : c'est le cloud gaming. Le Cloud computing, dans le contexte de jeu vidéo a beaucoup attiré l'attention en raison de ses facilités d'évolution, de disponibilité et capacité de calcul. Cependant, les systèmes de cloud gaming actuels ont des exigences très fortes en termes de ressources réseau, réduisant ainsi l'accessibilité et l'ubiquité des jeux dans le cloud, car les dispositifs clients avec peu de bande passante et les personnes situées dans la zone avec des conditions de réseau limitées et/ou instables, ne peuvent pas bénéficier de ces services de cloud computing. Dans cette thèse, nous présentons une technique d'adaptation inspirée par l'approche du niveau de détail (Level of detail) dans les graphiques 3D. Elle est basée sur un paradigme du cloud gaming dans l'objectif de fournir une accessibilité multi-plateforme, tout en améliorant la qualité d'expérience (QoE) du joueur en réduisant l'impact des mauvaises conditions réseau (delai, perte, gigue) sur l'interactivité et réactivité du jeu. Notre première contribution se compose de modèles de jeu reliant les objets du jeu à leurs besoins en termes de communication représentés par leurs importances dans le jeu. Nous avons ensuite fourni une approche de niveau de détail pour gérer la distribution des ressources réseau basée sur l'importance des objets dans la scène et les conditions réseau. Nous validons notre approche en utilisant des jeu prototypes et evaluons la QoE du joueur, par des expériences pilotes. Les résultats montrent que le framework proposé fournit une importante amélioration de la QoE. / With the arrival of cloud computing technology, game accessibility and ubiquity havea bright future. Games can be hosted in a centralize server and accessed through theInternet by a thin client on a wide variety of devices with modest capabilities: cloudgaming. Some of the advantages of using cloud computing in game context includes:device ubiquity, computing exibility, affordable cost and lowered set up overheads andcompatibility issues. However, current cloud gaming systems have very strong requirementsin terms of network resources, thus reducing their widespread adoption. In factdevices with little bandwidth and people located in area with limited network capacity,cannot take advantage of these cloud services. In this thesis we present an adaptationtechnique inspired by the level of detail (LoD) approach in 3D graphics. It is based ona cloud gaming paradigm in other to maintain user's quality of experience (QoE) byreducing the impact of poor network parameters (delay, loss, bandwidth) on game interactivity.Our first contribution consist of game models expressing game objects and theircommunications needs represented by their importance in the game. We provided twodifferent ways to manage objects' importance using agents organizations and gameplaycomponents. We then provided a level of detail approach for managing network resourcedistribution based on objects importance in the game scene and network conditions. Weexploited the dynamic objects importance adjustment models presented above to proposeLoD systems adapting to changes during game sessions. The experimental validation ofboth adaptation models showed that the suggested adaptation minimizes the effects oflow and/or unstable network conditions in maintaining game responsiveness and player'sQoE.

Collaborative design inträffar när flera aktörer samarbetar för ett gemensamt mål eller intresse som inte kan åstadkommas ensamt. Collaborative design sker antingen i ett co-located möte ”ansikte mot ansikte” eller distribuerat möte ”distansmöte”. Distribuerade möten, oftast via ett nätverkssystem, sker då olika aktörer av ett projekt inte befinner sig i närheten av varandra. Målet med distribuerad kommunikation är att kunna återskapa det fysiska mötet i ett virtuellt möte.  Syftet med denna studie är utveckling av en kommunikationsmetod som med hjälp av förstärkt verklighet kan visualisera och överföra information mellan arkitekt och beställaren i ett distribuerat möte. Metoden baseras på mjukvaruutveckling i spelmotorer vilka har kapacitet för skapande av realtidsvisualiseringar i kombination med flera skript som kan utföra många komplexa funktioner, inklusive synkron dataöverföring. Då examensarbetet fokuserar på distribuerad kommunikation har mjukvaruutvecklingen begränsats till endast smarta mobiltelefoner, detta på grund av stora tillgängligheten till enheten i allmänheten. Ett ytterligare syfte är undersökning om hur överföring av BIM kan simplifieras och automatiseras till spelmotorn Unity.  Utvecklingen av demonstratorn visar att BIM-överföring kan ske via scheman skapade i BIMmjukvaror såsom Autodesk Revit som inläses av skript i Unity. Överföringsmetoden visualiserar BIM i realtid och även skapandet av funktioner som integrerar BIM, inklusive våningsplanväljare och lagervisningsväxlare. Systemet för nätverkssynkronisering möjliggör synkron kommunikation mellan alla aktörer genom användande av funktioner och flera skript som möjliggör positionssynkning, skärmdelning och objektdelning. Resultatet från studien gällande förstärkt verklighet har kombinationen av fördelar och nackdelar varierade beroende på aktörernas erfarenhet. Den utvecklade mjukvaran med tillhörande metod visar på potential för användning gällande distribuerad kommunikation. / Collaborative design occurs when individuals work together to achieve a common goal or interest that cannot be accomplished alone. Collaborative design take place either in a co-located meeting “face to face” or a distributed meeting “distance meeting”. Distributed meetings, often via a networking system, occur when individuals of a project don’t have the opportunity for a colocated meeting. The goal of distributed communication is to be able to recreate the physical confrontation in a virtual meeting.  The purpose of this study is to develop a communication software that, with addition of augmented reality, can visualize and share information between architects and clients in a distributed meeting. For software development game engine Unity is used, which has the capacity to create a real-time visualization in combination with scripts that can add features such as synchronous data transfer. As the thesis focuses on distributed communication a limitation has been put on used devices to only consider smartphones, this is due to the high level of availability of the device in general. An additional purpose of the thesis is to simplify and automate BIM transfer to Unity game engine. The development of a demonstrator shows that BIM transfer can be done via usage of schedules that can be created in BIM software such as Autodesk Revit, which is later read by scripts in Unity. The software visualizes BIM in real time and supports creation of functions that can integrate with BIM, including plan selector “våningsplanväljare” and layer manager “lagervisningsväxlare”. The network synchronization system enables synchronous communication between all users, using functions such as position sync, screen sharing and object sharing. There has been a combination of advantages and disadvantages for augmented reality that varied depending on individual experience. The developed software with methods has potential for usage in use of distributed communication.