Sip Based Mobile Voice Over Ip Client For Wireess Networks

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2008Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2008Bu tez SIP tabanlı mobile bir VoIP istemcisinin tasarımını ve gerçeklenmesini tanımlar. Bu tez temelde çoktürel ağlar üzerinde çalışabilen bir VoIP istemcisi tasarımının çözülmesi gereken iki sorununun üzerinde yogunlaşır. Birinci ve en zorlu sorun farklı erişim teknolojileri arasında kullanıcıya fark ettirmeden yer değişim desteği sağlanmasıdır. Bu tezde, kullanıcıya fark ettirmeden el değiştirme yönetimi, uygulama katmanında, multimedya oturumunu başlatmak, sonlandırmak ve değiştirmek için kullanılan Oturum Başlatma Protokolü (SIP) kullanılarak ele alınmıştır. SIP yaygın bir şekilde kabul edilmekte olan bir VoIP standartıdır. Kullanıcıya fark ettirmeden el değiştirmeyi destekleyebilmek için, VoIP istemcisi üzerinde çalışan SIP tabanlı bir bağlantı yöneticisi önerilmiştir. Bağlantı yöneticisi yeni ağlar keşfettiğinde, adaylar listesinden bir ağ seçer ve hali hazırda yürütülmekte olan iletişimi kullanıcıya fark ettirmeden yeni ağ arayüzüne aktarır. Dolayısı ile, bu birim Wi-Fi, 3G gibi çoktürel ağlar arasında dolaşmayı sağlar. İkinci sorun ise, en kaliteli çağrı (arama) desteğini sağlamaktır. En kaliteli çağrı desteği, iletişim kurmak isteyen tarafların farklı türden ağlara bağlı olmaları durumunda, VoIP uygulamasının iletişim tipine (yarı-çift yönlü yada tam-çift yönlü) karar vermebilmesi demektir. Örneğin, eğer iletişim kurmak isteyen taraflardan biri bir GSM ağındaysa, en iyi çağrı kalitesini yakalayabilmek için, iletişim yarı-çift yönlü olarak kurulmalıdır. Bu tez, bahsedilen özelliği desteklemek için, istemci tabanlı bir karar mekanizması önerir. Bu karar mekanizması, iletişim kurulmak istenen tarafa, istemcinin içinde bulunduğu ağa göre belirlenmiş iletişim tipini içeren bir davet iletisi gönderir. Diğer istemci bu davet iletisini aldıktan sonra, aynı karar mekanizması, iletişimi “bas-konuş VoIP” yada “tam-çift yönlü VoIP” olarak ayarlar.This thesis describes the design and the implementation of a SIP-based mobile VoIP client. It mainly focuses on two challenges of designing a VoIP client which works on heterogeneous network environments. One and the most challenging problem is the provision of seamless mobility support among different access technologies. In this thesis, seamless handover management is handled at the application layer by using Session initiation protocol (SIP), which is used to initiate, terminate, and modify multimedia session. SIP is becoming a widely accepted standard for VoIP. To support seamless handover, a SIP based connection manager is proposed on VoIP client application. As new networks are discovered by the connection manager, it selects a new network from the candidate list and transfers the current communication to the new network interface seamlessly. Therefore, this module provides roaming across heterogeneous networks such as Wi-Fi, 3G. Second problem is providing the best effort call quality support. It means that if the communication parties are in dissimilar networks, the VoIP application should decide the communication type (half-duplex or full-duplex). For instance, if one of the communication parties is in a GSM network, then the communication should be established as a half-duplex manner to achieve best call quality. This thesis proposes a client-based decision mechanism to support this property. This decision mechanism sends an invite message including the communication type (half-duplex or full-duplex) of the client according to the network in which it operates to the other communication party. After the other client receives this invite message, same decision mechanism adjusts the communication as either a “push to talk VoIP” or a “full-duplex VoIP”.Yüksek LisansM.Sc

A platform for distributed learning and teaching of algorithmic concepts

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (p. 119-121).by Nathan D.T. Boyd.M.Eng

Design and implementation of a modular controller for robotic machines

This research focused on the design and implementation of an Intelligent Modular Controller (IMC) architecture designed to be reconfigurable over a robust network. The design incorporates novel communication, hardware, and software architectures. This was motivated by current industrial needs for distributed control systems due to growing demand for less complexity, more processing power, flexibility, and greater fault tolerance. To this end, three main contributions were made. Most distributed control architectures depend on multi-tier heterogeneous communication networks requiring linking devices and/or complex middleware. In this study, first, a communication architecture was proposed and implemented with a homogenous network employing the ubiquitous Ethernet for both real-time and non real-time communication. This was achieved by a producer-consumer coordination model for real-time data communication over a segmented network, and a client-server model for point-to-point transactions. The protocols deployed use a Time-Triggered (TT) approach to schedule real-time tasks on the network. Unlike other TT approaches, the scheduling mechanism does not need to be configured explicitly when controller nodes are added or removed. An implicit clock synchronization technique was also developed to complement the architecture. Second, a reconfigurable mechanism based on an auto-configuration protocol was developed. Modules on the network use this protocol to automatically detect themselves, establish communication, and negotiate for a desired configuration. Third, the research demonstrated hardware/software co-design as a contribution to the growing discipline of mechatronics. The IMC consists of a motion controller board designed and prototyped in-house, and a Java microcontroller. An IMC is mapped to each machine/robot axis, and an additional IMC can be configured to serve as a real-time coordinator. The entire architecture was implemented in Java, thus reinforcing uniformity, simplicity, modularity, and openness. Evaluation results showed the potential of the flexible controller to meet medium to high performance machining requirements

Datura: distributing activity in peer to peer collaborative virtual environments

Collaborative Virtual Environments (CVEs) are an exciting advance in the field of Virtual Reality (VR) research. By joining VR systems---and users---at widely scattered geographic locations, VR changes from an isolated experience to one of communication, interaction, and collaboration. Much research effort is being placed into the development of tools and techniques to power these collaborative experiences.;This dissertation describes the Datura toolkit for CVE development and, more importantly, the new concepts and methods that make Datura unique. We focus on the idea of Location of Computation (LoC)---methods for determining where, among all the sites participating in a CVE, particular calculations or particular decisions should be made. Datura connects sites into a peer to peer network, allowing each one to participate fully in bringing the virtual world to life.;Datura works at the level of elements---individual components that imbue shared objects with data, behaviors, and capabilities. These elements are shared among all sites, and control over them can be granted or migrated individually. This dissertation discusses the mechanisms for transferring control and computation, and provides a system for deciding where control should reside for each element in a CVE. An extensive set of tests and evaluations are also described, verifying the capabilities of the Datura system and demonstrating the performance and error-handling gains that are made by this fine-grained control over the location of computation

Quality-oriented adaptation scheme for multimedia streaming in local broadband multi-service IP networks

The research reported in this thesis proposes, designs and tests the Quality-Oriented Adaptation Scheme (QOAS), an application-level adaptive scheme that offers high quality multimedia services to home residences and business premises via local broadband IP-networks in the presence of other traffic of different types. QOAS uses a novel client-located grading scheme that maps some network-related parameters’ values, variations and variation patterns (e.g. delay, jitter, loss rate) to application-level scores that describe the quality of delivery. This grading scheme also involves an objective metric that estimates the end-user perceived quality, increasing its effectiveness. A server-located arbiter takes content and rate adaptation decisions based on these quality scores, which is the only information sent via feedback by the clients. QOAS has been modelled, implemented and tested through simulations and an instantiation of it has been realized in a prototype system. The performance was assessed in terms of estimated end-user perceived quality, network utilisation, loss rate and number of customers served by a fixed infrastructure. The influence of variations in the parameters used by QOAS and of the networkrelated characteristics was studied. The scheme’s adaptive reaction was tested with background traffic of different type, size and variation patterns and in the presence of concurrent multimedia streaming processes subject to user-interactions. The results show that the performance of QOAS was very close to that of an ideal adaptive scheme. In comparison with other adaptive schemes QOAS allows for a significant increase in the number of simultaneous users while maintaining a good end-user perceived quality. These results are verified by a set of subjective tests that have been performed on viewers using a prototype system

Role of Wireless technology in mobile augmented reality system (MARS)

Not availabl

Design and Implementation of a Credible Blockchain-based E-health Records Platform

Masters of ScienceWith the development of information and network technologies, Electronic Health Records (EHRs) management system has gained wide spread application in managing medical records. One of the major challenges of EHRs is the independent nature of medical institutions. This non-collaborative nature puts a significant barrier between patients, doctors, medical researchers and medical data. Moreover, unlike the unique and strong anti-tampering nature of traditional paper-based records, electronic health records stored in centralization database are vulnerable to risks from network attacks, forgery and tampering. In view of the data sharing difficulties and information security problems commonly found in existing EHRs, this dissertation designs and develops a credible Blockchain-based electronic health records (CB-EHRs) management system. To improve security, the proposed system combines digital signature (using MD5 and RSA) with Role-Based Access Control (RBAC). The advantages of these are strong anti-tampering, high stability, high security, low cost, and easy implementation. To test the efficacy of the system, implementation was done using Java web programming technology. Tests were carried out to determine the efficiency of the Delegated Byzantine Fault Tolerance (dBFT) consensus algorithm, functionality of the RBAC mechanism and the various system modules. Results obtained show that the system can manage and share EHRs safely and effectively. The expectation of the author is that the output of this research would foster the development and adaptation of EHRs management system

Automating System-Level Data-Interchange Software Through a System Interface Description Language

RÉSUMÉ Les plates-formes d'aujourd'hui, telles que les simulateurs de missions (FMS), présentent un niveau sans précédent d'intégration de systèmes matériels et logiciels. Dans ce contexte, les intégrateurs de systèmes sont confrontés à une hétérogénéité d'interfaces système qui doivent être alignées et reliées ensemble afin de fournir les capacités prévues d'une plate-forme. Le seul aspect des échanges de données système est problématique allant de données désalignées jusqu'à des environnements multi-architecturaux utilisant différents types de protocoles de communication. Les intégrateurs sont également confrontés à des défis similaires lors de l'interaction de multiples plates-formes ensemble à travers des environnements de simulation distribuée où chaque plate-forme peut être considérée comme un système avec sa propre interface distincte. D'autre part, permettre la réutilisation de système à travers diverses plates-formes en support aux gammes de produits est un défi pour les fournisseurs de systèmes, car ils doivent adapter leurs interfaces système à des plates-formes hétérogènes faisant donc face aux mêmes difficultés que les intégrateurs. En outre, l'introduction de modifications aux interfaces système afin de répondre aux besoins tardifs d'affaires, ou à des contraintes de performance imprévues, par exemple, est d'autant plus ardue que leurs impacts sont difficiles à prévoir et que leurs effets sont souvent décelés tard dans le processus d'intégration. En conséquence, cette thèse aborde la nécessité de simplifier l'intégration et l'interopérabilité système afin de réduire leurs coûts associés et d'accroître leur efficacité ainsi que leur efficience. Elle est destinée à apporter de nouvelles avancées dans les domaines de l'intégration système et de l'interopérabilité système. Notamment, en établissant une taxonomie commune, et en augmentant la compréhension des interfaces système, des divers aspects impactant les échanges de données système, des considérations des environnements multi-architecturaux, ainsi que des facteurs permettant la gouvernance d'interface ainsi que de la réutilisation système. À cette fin, deux objectifs de recherche ont été formulés. Le premier objectif vise à définir un langage utilisé pour décrire les interfaces système et les divers aspects entourant leurs échanges de données. Par conséquent, trois aspects principaux sont étudiés relatifs aux interfaces système: les éléments de langage pertinents utilisés pour les décrire, la modélisation des interfaces système avec ce langage, et la capture des considérations multi-architecturales. Le second objectif vise à définir une méthode pour automatiser le logiciel responsable des échanges de données système comme moyen pour simplifier les tâches impliquées dans l'intégration et l'interopérabilité système. Par conséquent, les compilateurs de modèles et les techniques de génération de code sont étudiés. La démonstration de ces objectifs apporte de nouvelles avancées dans l'état de l'art de l'intégration système et de l'interopérabilité système. Notamment, ceci culmine en un nouveau langage de description d'interface système, SIDL, utilisé pour capturer les interfaces système et les divers aspects entourant leurs échanges de données, ainsi qu'en une nouvelle méthode pour automatiser le logiciel d'échange de données au niveau système à partir des interfaces systèmes capturées dans ce langage. L'avènement de SIDL contribue également une nouvelle taxonomie fournissant une perspective complète sur l'interopérabilité système ainsi qu'en un langage commun qui peut être partagé entre les parties prenantes, tels que les intégrateurs, les fournisseurs et les experts système. Étant agnostique aux architectures, SIDL fournit un seul point de vue architectural supervisant toutes les interfaces système et capture les considérations multi-architecturales ce qui n'a jamais été réalisé avant ce travail. D'autant plus, un générateur de code SIDL est introduit présentant la nouveauté de générer le logiciel d'échange de données à partir d'un bassin plus riche d'information, notamment à partir des relations système de haut niveau allant jusqu'au bas niveau couvrant les détails protocolaires et d'encodage. En raison des considérations multi-architecturales qui sont capturées nativement dans SIDL, ceci permet au générateur de code d'être agnostique aux architectures le rendant réutilisable dans d'autres contextes. Cette thèse ouvre également la voie à de futures recherches bâtissant sur ses contributions. Elle propose même une vision pour le développement d'applications logicielles avec comme objectif final de repousser encore plus loin les limites de la simplification et de l'automatisation des tâches liées à l'intégration et à l'interopérabilité système.----------ABSTRACT Today’s platforms, such as full mission simulators (FMSs), exhibit an unprecedented level of hardware and software system integration. In this context, system integrators face heterogeneous system interfaces which need to be aligned and interconnected together in order to deliver a platform's intended capabilities. The sole aspect of the data systems exchange is problematic ranging from data misalignment up to multi-architecture environments over varying kinds of communication protocols. Similar challenges are also faced by integrators when interoperating multiple platforms together through distributed simulation environments where each platform can be seen as a system with its own distinct interface. On the other hand, enabling system reuse across multiple platforms for product line support is challenging for system suppliers, as they need to adapt system interfaces to heterogeneous platforms therefore facing similar challenges as integrators. Furthermore, the introduction of system interface changes in order to respond to late business needs, or unforeseen performance constraints for instance, is even more arduous as impacts are challenging to predict and their effect are often found late into the integration process. Consequently, this thesis tackles the need to simplify system integration and interoperability in order to reduce their associated costs and increase their effectiveness along with their efficiency. It is meant to bring new advances in the fields of system integration and system interoperability. Notably, by establishing a common taxonomy, and by increasing the understanding of system interfaces, the various aspects impacting system data exchanges, multi-architecture environment considerations, and the factors enabling interface governance as well as system reuse. To this end, two research objectives have been formulated. The first objective aims at defining a language used to describe system interfaces and the various aspects surrounding their data exchanges. Therefore, three key aspects are studied relating to system interfaces: the relevant language elements used to describe them, modeling system interfaces with the language, and capturing multi-architecture considerations. The second objective aims at defining a method to automate the software responsible for system data exchanges as a way of simplifying the tasks involved in system integration and interoperability. Therefore, model compilers and code generation techniques are studied. The demonstration of these objectives brings new advances in the state of the art of system integration and system interoperability. Notably, this culminates in a novel system interface description language, SIDL, used to capture system interfaces and the various aspects surrounding their data exchanges, as well as a new method for automating the system-level data-interchange software from system interfaces captured in this language. The advent of SIDL also contributes a new taxonomy providing a comprehensive perspective over system interoperability as well as a common language which can be shared amongst stakeholders, such as integrators, suppliers, and system experts. Being architecture-agnostic, SIDL provides a single architectural viewpoint overseeing all system interfaces and capturing multi-architecture considerations which was never achieved prior to this work. Furthermore, a SIDL code generator is introduced which has the novelty of generating the data-interchange software from a richer pool of information, notably from the high-level system relationships down to the low-level protocol and encoding details. Because multi-architecture considerations are captured natively in SIDL, this enables the code generator to be architecture-agnostic making it reusable in other contexts. This thesis also paves the way for future research building upon its contributions. It even proposes a vision for software application development with the end goal being to push further the boundaries of simplifying and automating the tasks involved in system integration and interoperability