Signaling For Multimedia Conferencing in Stand-Alone Mobile Ad Hoc Networks

Mobile ad hoc networks (MANETs) are infrastructure-less and can be set up anywhere, anytime. They can host a wide range of applications in rescue operations, military, private, and commercial settings. Multimedia conferencing is the basis of a wealth of “killer†applications that can be deployed in MANETs. Some examples are audio/video conferencing, multiplayer games, and online public debating. Signaling is the nerve center of multimedia conferences—it establishes, modifies, and tears down conferences. This paper focuses on signaling for multimedia conferences in MANETs. We review the state of the art and propose a novel architecture based on application-level clusters. Our validation employed SIP as the implementation technology and OPNET as our simulation tool. Our clusters are constructed dynamically and the nodes that act as cluster heads are elected based on their capabilities. The capabilities are published and discovered using a simple application-level protocol. The architectural principles and the clustering operations are discussed. Our SIP-based implementation is also presented along with the performance evaluation. Keywords: MANET, SIP-technology, OPNET-simulation tool, cluste

Controlador de conferências para sistemas colaborativos

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Ciência da Computação.Trabalhos colaborativos são atividades conduzidas por grupos de indivíduos apresentando diferentes requisitos e tarefas a serem executadas. Em geral, devido à diversidade em termos de tarefas a serem executadas, um único sistema de trabalho colaborativo não consegue atender as necessidades de todos os possíveis tipos de trabalho colaborativo. Conseqüentemente, os usuários precisam usar um conjunto de ferramentas, que satisfaçam suas necessidades. Normalmente estas ferramentas são usadas em paralelo, sem nenhuma integração efetiva. Esta integração permite que diferentes funcionalidades de colaboração sejam dinamicamente combinadas e controladas de acordo com as necessidades. Uma das contribuições neste sentido é o ambiente de integração LEICA (Loosely-coupled Environment for Integrating Collaborative Applications), que permite estender as funcionalidades do ambiente colaborativo através da agregação de novas ferramentas. Um dos elementos fundamentais para um ambiente de colaboração é a comunicação efetiva entre os participantes, implementada por uma ferramenta de conferência. Na perspectiva de compor estes sistemas, uma ferramenta de conferência idealmente deveria permitir a sua integração com outras ferramentas colaborativas. Este trabalho apresenta um controlador de conferências junto a um servidor PBX Asterisk, compondo uma ferramenta que pode ser utilizada em outras aplicações colaborativas, permitindo novas funcionalidades de comunicação. A solução de integração dessas aplicações colaborativas adotadas neste trabalho foi o ambiente LEICA. Como experimento realizado este controlador foi integrado a um ambiente de co-navegação CoLab para este disponibilizar suporte a conferências

A SOAP Web Services-Based Architecture for Floor Control in Multimedia Conferencing

Multimedia conferencing applications are an important and widely-used category of Web applications. Floor control is a significant and advanced feature of multimedia conferencing applications. Floor control mechanisms, when introduced in audio/video conferencing, control the media streams such as identifying which participant is allowed to send and who can be seen or heard. This prevents conflict and ensures an optimized use of resources between the conference participants. Floor control is composed of three logical entities: a single floor control server (i.e. entity responsible for managing the floors and their status), one or more floor chairs (moderators), and any number of regular conference participants. This thesis proposes a SOAP Web services based architecture for floor control in multimedia conferencing. Web services are designed to support interoperable machine-to-machine interaction over a network. They are attractive because of their flexibility. There are two types of web services: SOAP Web services and RESTful Web services. In SOAP Web services, interactions between the entities are based on XML and use SOAP, which is embedded in HTTP. RESTful web services are an architectural design style that rely on HTTP, but do not use SOAP. XML is also optional. We propose a set of floor control requirements and use them to review the related work and pinpoint the weaknesses. The proposed architecture includes the main components of floor control. It also includes a comprehensive set of server-side and client-side SOAP web service APIs that expose the floor control capabilities to application developers. The proposed APIs are programming language-independent and provide a higher level of abstraction to the application developers, which enables the interoperability. Furthermore, in the proposed architecture the floor control clients do not interact directly with the floor control server (FCS) but through a gateway accessible using SOAP web services. This opens up the possibility to use different floor control protocols transparently to the floor control clients. Application portability is no longer a problem because floor clients access the floor capabilities independently of the protocol supported by the FCS. We have built a conferencing application with floor control as a proof of concept to demonstrate the new interface for floor control and the feasibility of the proposed architecture. In addition, performance measurements have also been made to evaluate the viability of the architecture

Multiparty/Multimedia Conferencing in Mobile Ad-Hoc Networks for Improving Communications between Firefighters

In current practice, firefighters’ communications systems are verbal, using a simplex Radio Frequency (RF) system (walkie-talkie). They use a push-to-talk mechanism in which only one person can talk at any time and all other firefighters will hear the messages. They use special codes (e.g. 1008, 1009, etc.) to express their current situation. Firefighters of the same team need to be in visual contact with each other at all times. This RF system does not support other functionalities (e.g. video communications, conference calls). In addition, because communication between firefighters is a flat structure, private communications is not possible. Mobile Ad-Hoc Networks (MANETs) are infrastructure-less and self-organized wireless networks of mobile devices, which are not based on any centralized control. MANETs are suitable for the hosting of a wide range of applications in emergency situations, such as natural or human-induced disasters, and military and commercial settings. Multimedia conferencing is an important category of application that can be deployed in MANETs. This includes well-known sets of applications, such as audio/video conferencing, data communications, and multiplayer games. Conferencing can be defined as the conversational exchange of data content between several parties. Conferencing requires, at the very least, the opening of two sessions: a call signaling session, and a media handling session. Call signaling is used to set up, modify, and terminate the conference. Media handling is used to cover the transportation of the media, and to control/manage the media mixers and media connections. So far, very little attention has been devoted to the firefighters’ communication system. In the present work, we focus on building a new communication system for firefighters using multimedia conferencing/sub-conferencing in MANETs. The background information for the firefighters’ current communications system and MANETs, along with the multimedia conferencing, is provided. The limitations of this system are determined, and the requirements are derived to determine the functionalities of a better communication system that will overcome current limitations. We have proposed a cluster-based signaling architecture that meets our requirements. We have also identified a state-of-the-art media handling and mixing system that meets most of our requirements, and have adapted it to inter-work with our signaling system. We have implemented the proposed architecture using SIP signaling protocol. Performance measurements have been performed on the prototype. Through experiments, we have found that the new multimedia communication system is a very promising approach to solve the current firefighters’ communication problems

A Cloud Platform-as-a-Service for Multimedia Conferencing Service Provisioning

Multimedia Conferencing is the real-time exchange of media content (e.g. voice, video and text) between multiple participants. It is the basis of a wide range of conferencing applications such as massively multi-player online games and distance learning applications. For faster development as well as cost efficiency, developers of such conferencing applications can use conferencing services (e.g. dial-in audio conference) provided by third-parties. However, the third-party service providers face several challenges with respect to conferencing service provisioning (i.e. service development, deployment and management). One challenge is mastering complex low-level details of conferencing technologies, protocols and their interactions. Another challenge is resource elasticity. Number of conference participants varies during runtime. So resource utilization in an elastic manner is a critical factor to achieve cost efficiency. Cloud Computing can help tackle these challenges. It is a paradigm for swiftly provisioning a shared pool of configurable resources (e.g. services, applications, network and storage) on demand. It has three main service models: Infrastructure-as-a-Service (IaaS), Platform-as-a-Service (PaaS) and Software-as-a-Service (SaaS). Using a PaaS, service providers can provision conferencing services easily and offer them as SaaS. Nonetheless, cloud-based provisioning of conferencing services still remains a big challenge due to the shortcomings of existing PaaS. In this thesis, a PaaS architecture for conferencing service provisioning is proposed. It is based on a business model from the state of the art. It relies on conferencing IaaSs that, instead of VMs, offer conferencing substrates (e.g. dial-in signaling, video mixer and audio mixer). The conferencing PaaS enables composition of new conferences from substrates on the fly. Moreover, it provides conferencing service providers, who are experienced in programming, with high-level interfaces to abstract the internal complexities of conferencing. In order for PaaS to scale ongoing conferences elastically, an algorithm is also presented in this thesis. The conferencing PaaS is prototyped and performance measurements are made. The proposed algorithm’s performance is also evaluated

Signaling for conferencing in mobile ad hoc networks

Mobile Ad hoc NETworks (MANETs) are networks that do not need to be pre-configured. They are composed of transient nodes connected through wireless interfaces. Due to their flexibility, the ease to build and the associated low cost, they are gaining more and more momentum. They are also seen as part of the fourth generation wireless networks. New applications, such as conferencing, are emerging for such networks. Conferencing enables a set of applications such as audio/video conferencing, debating, distance-learning and multi-party gaming. The implementation of conferencing in MANETs is not an easy task due to scarce network resources, heterogeneous devices, frequently changing topology and unstable wireless connections. It challenges each technical aspect of conferencing: signaling, media handling and conference control. Signaling is the control component of conferencing. It handles the session initiation, modification and termination. In this work, we focus on signaling for conferencing in MANETs. Two types of MANETs are considered: standalone MANETs and integrated MANETs/3G networks. Background information is provided, requirements are derived and the state of the art, including signaling protocols such as SIP and H.323, are reviewed. Since there is no existing solution that meets all of the derived requirements, we propose a novel cluster-based signaling architecture that meets the requirements of signaling for standalone MANETs. The clusters are application-layer clusters that are dynamically created and deleted for a conference. We also propose a signaling architectures for integrated MANETs/3G networks. The solution is based on conference gateways. We implement the architectures using SIP extensions. Experimental results are obtained from prototypes and OPNET based simulations. In the prototype, we built the signaling system on a small scale network using IEEE 802.11 ad hoc settings. In the OPNET simulation, we use MANET features. From experiments, we found that clustering is a very promising approach for solving signaling problems in MANETs. Being aware of several performance issues of our signaling systems, we further propose optimization schemes that are based on cross-layer design. We also implement some of these schemes and apply them to our signaling systems. The evaluation shows that the schemes significantly improve the signaling performance

Bedarfsgesteuerte Verteilung von Inhaltsobjekten in Rich Media Collaboration Applications

IP-basierte Konferenz- und Kollaborations-Systeme entwickeln sich mehr und mehr in Richtung Rich Media Collaboration, d.h. vereinigen Audio- und Videokonferenzfunktionalität mit Instant Messaging und kollaborativen Funktionen wie Presentation Sharing und Application Sharing. Dabei müssen neben den Live-Medienströmen auch Inhaltsobjekte wie Präsentationsfolien oder Dokumentseiten in Echtzeit innerhalb einer Session verteilt werden. Im Gegensatz zum klassischen 1:n-push-Schema wird dafür in der Arbeit ein Ansatz für wahlfreien Zugriff auf durch die Teilnehmer selbst gehostete Inhaltsobjekte - also n:m-pull-Verteilung - vorgestellt. Dieser Ansatz hat in Anwendungsszenarien mit gleichberechtigten Teilnehmern, wie zum Beispiel virtuellen Meetings von Projektteams, signifikante Performance-Vorteile gegenüber den traditionellen Ansätzen. Mit dem Content Sharing Protocol (CSP) wurde eine Protokoll-Engine bestehend aus neun Mikroprotokollen entwickelt, implementiert und evaluiert. Sie beinhaltet neben der Kernfunktionalität der Inhaltsauslieferung auch Unterstützung für Caching, Prefetching und Datenadaption, sowie dynamische Priorisierung von Datentransfers und Interaktionsunterstützung