MOFA: a model for fault and availability in complex services

Asset allocation to optimize reliability and availability (R&A) has been studied in the literature. However, these concepts have not been investigated in combination with degraded performance in realistic reliability-models. Some reliability models, techniques, and tools allow modeling of degradable performance. However, they are mainly used in evaluating R&A of given systems; they do not consider the inverse problem of determining the system parameters that would maximize the R&A. This paper provides a realistic reliability model for complex services; the model can be used to study the asset allocation problem in degradable complex services. This paper uses a simple model to describe the failure characteristics of the system parts. This model provides: (1) an infrastructure for defining R&A in a flexible way, and (2) a way of defining at what level of availability it is worth offering the service, and at what level of failure of resources the system should be declared faulty. This model is then used to `allocate optimally the available assets' to `implement a service that is tailored to the availability needs of the user and the situation'. The model is applied to a realistic example of a complex service, viz. a multimedia communication service     

A signaling protocol for complex multimedia services

The author introduces a signaling protocol for user applications that invokes multimedia services provided by the EXPANSE research prototype, a broadband ISDN testbed. A generic framework that flexibly accommodates a wide variety of services involving multiple parties with heterogeneous terminals is described. The author describes the generic services supported, introduces the EXPANSE call model, discusses syntax and message flow procedures, and relates EXPANSE signaling to the ISDN signaling control part (ISCP) and long-term broadband ISDN signaling work currently under study by CCITT     

A new scheme to achieve weighted fairness for WLAN supporting multimedia services

This work presents a new scheme which exploits differentiations of both inter frame space (IFS) and contention window (CW) to achieve weighted fairness for two classes of services under enhanced distributed channel access (EDCA) mode in an 802.11e WLAN. Given the arbitration IFSs (AIFSs), the proposed scheme can properly set the corresponding CWs such that the ratio of the two classes' successful transmission probabilities can attain a pre-defined weighted-fairness goal. Additionally, the throughput and delay of the two classes of services are derived. The simulation results compare well with the analytical results. Also, the analytical results illustrate that the proposed scheme can achieve a fairness index very close to 1 and attain a greater aggregate throughput with lower collision probability than the CW differentiation scheme presented in A. Banchs and X. Perez (2002), for a specified weighted-fairness goal.     

Congestion control for multimedia services

The problem of congestion control in high-speed networks for multimedia traffic, such as voice and video, is considered. It is shown that the performance requirements of high-speed networks involve delay, delay-jitter, and packet loss. A framing congestion control strategy based on a packet admission policy at the edges of the network and on a service discipline called stop-and-go queuing at the switching nodes is described. This strategy provides bounded end-to-end delay and a small and controllable delay-jitter. The strategy is applicable to packet switching networks in general, including fixed cell length asynchronous transfer mode (ATM), as well as networks with variable-size packets     

一种适合多媒体处理的新型芯片

介绍ＭＭＸ技术的基本内容及带有ＭＭＸ技术的微处理器，以ＭＭＸ技术在视频会议系统上的应用为例，侧重分析ＭＭＸ技术给多媒体与通信应用带来的性能改善，并对ＭＭＸ技术的应用及发展前景进行探讨。     

Frequency-hopping codes for multimedia services in mobiletelecommunications

In this paper, “multilength” frequency-hopping (FH) codes are constructed by modifying the generalized prime codes (GPCs). The new codes have asymptotically optimal cardinality as well as zero autocorrelation sidelobes and cross-correlation functions of no greater than one. They are suitable for the integration of multimedia services (e.g., data, voice, image, and video) with different quality-of-service (QoS) requirements and signaling rates in future telecommunication systems, such as third-generation cellular mobile radio systems, where rate and service quality are dynamically matched to users' needs through the assignment of different-length FH patterns. The use of the new codes in multirate multimedia systems with FH code-division multiple access (FH-CDMA) is illustrated. Providing frequency and time diversities, the applications of the GPCs to an FH time-division multiple-access (FH-TDMA) and FH/time-hopping TDMA (FH/TH-TDMA) system are also discussed. Finally, the use of the codes in optical CDMA systems as multiwavelength optical orthogonal codes is studied     

DAVIC and interactive multimedia services

DAVIC is establishing the industry standard for end-to-end interoperability of broadcast and interactive digital audio-visual information. Its published specifications, DAVIC 1.0-1.4, are backward compatible and form the foundation for commercial interactive multimedia experiences. Each specification is market-driven and developed where possible in close synergy with the products and work in progress of other standards-developing organizations. In addition, DAVIC 1.3.1 has been submitted as a Draft International Standard to ISO/IEC JTC 1 in order to establish this industry specification as a recognized international standard and to contribute to the international standards community. DAVIC's future goals are clear, and significant progress is being made on achieving TV anytime/anywhere as the next stage to full interactive multimedia services     

Partial order connections : a new concept for high speed and multimedia services and protocols

This paper presents a new concept that has been developed to define high performance multimedia data transfers between communicating entities. All current protocols use either connectionless (Cl) or connection-oriented (Co) approaches and many mechanisms have been proposed in each case. Both sets of present Cl and co protocols are not conceptually related and there is a design gap between the definition and use of these two families. A new concept, a partial order connection (Poc), is defined here. It will be seen that Cl and Co approaches are two specific cases of the much more general concept presented here. More precisely, a Poc is an end-to-end connection that provides a partial order service where the objects can be delivered to the users in a different order from the transmitted order. It is first shown how this new concept has emerged and what are its interests in terms of resources. Then a formal definition of reliable and unreliable Pocs and a way to measure their complexity will be given. It is shown how such a generalized connection can be used and how time constraints can be handled in an integrated way, leading to the definition of a design space for protocols.     

A temporal model for interactive multimedia scenarios

Many authoring tools let authors create scenarios, but very few let them create an active multimedia scenario that will not only play itself back, but will change course dynamically, depending on user interactions. Our temporal model provides a new way to represent asynchronous and synchronous temporal events, allowing authors to create scenarios that offer viewers seamless, transparent options     

Information modeling and handling for context-aware multimedia services

This article presents research challenges in wireless ad hoc networks supporting context-aware multimedia services from the point of view of different context-modeling approaches and a system architecture for context handling and delivery. Modeling techniques for context information are classified into six different categories and benchmarked according to their support with regard to 12 service requirements described in this work. One of these modeling techniques is used in the framework of a distributed context handling and delivery system that is also part of this article's contribution and a representative wireless ad hoc application scenario is presented. This end user scenario and many others are possible thanks to the flexibility and adaptability of the above mentioned context handling and delivery system     

A playback schedule model for multimedia documents

Multimedia documents differ significantly from traditional documents composed of text and geometric graphics. The introduction of continuous media such as audio, video, and computer-generated graphics imposes new requirements on document representation and information storage. We designed an architecture for creating multimedia documents by means of a logical structure, a layout structure, and a rendering scenario, which is a schedule for document playback     

IP-based access networks for broadband multimedia services

The increasing demands of new services and applications are pushing for drastic changes in the design of access networks for residential and SOHO users. Future access networks will provide full service integration, resource sharing at the packet level, and QoS support. It is expected that using IP as the base technology, the ideal plug-and-play scenario, where the management actions of the access network operator are kept to a minimum, will be achieved easily. In this article we start by giving a historical perspective of the evolution of access networks. We then describe an IP-based architecture targeted for integrated support of broadband multimedia services, designed to be low-cost and easily manageable. We illustrate the different phases of a multimedia Internet access session, when using SIP for session initiation, COPS and DIAMETER for QoS policy management, and AAA and RSVP for resource reservation.     

EuroBridge: communications services for multimedia applications

The aim of the EuroBridge project is to provide a uniform communication service platform. This platform will provide true multimedia multipoint services including interactive video conferencing and store-and-forward data services. The project will enhance selected OSI application layer services to provide them with multimedia capabilities. Selection of the initial services as well as the identification of necessary functional enhancements were based on actual user requirements. To support the dedicated communication requirements imposed by multimedia and multipoint applications, the lower layers of the OSI model will be enhanced accordingly. This includes designing and implementing new lightweight session and presentation protocols, respectively. Furthermore, high-speed transport protocols will be utilised. The actual protocol stack used will be configured dynamically depending on the requested quality of service. Support of multicast capabilities will be a crucial issue. The service platform is being implemented to run on top of different high-speed networks, including FDDI and DQDB     

Policy-driven personalized multimedia services for mobile users

This paper proposes an agent-based service provisioning system for mobile users. It describes a set of cooperative agents distributed over different sites that work together to provide personalized services for mobile users over the Internet. Users moving outside the office are able to maintain an off ice-like environment at home, or at temporary locations such as a meeting at another company, a business trip, or a hotel. Agents representing the end-users and the system agents engage in a negotiation process to facilitate access to personalized services at other sites. This access is obtained in accordance with the users' home policies as well as those at their current location. An Adaptive Service Presentation agent is used to adapt the service presentation to the capabilities of the users' workstations, laptops, phones, PDAs, or other devices. This work is conducted in Canada as part of the Mobile Agent Alliance project involving the University of Ottawa, the National Research Council, and the Mitel Corporation.     

Editorial: Technologies for interactive multimedia services

The last few years have witnessed a significant development in the means to produce and make available multimedia content, namely owing to the democratisation of access to digital picture and video cameras in addition to the generalisation of Internet usage. The trend now is to allow ubiquitous access to this ever-increasing amount of multimedia content, enabling a user to find effectively the desired information. This Special Section of IEE Proceedings Vision, Image & Signal Processing addresses some of the enabling technologies for providing interactive multimedia services. All the papers in this Special Section correspond to extended versions of papers presented at the 5th International Workshop on Image Analysis for Multimedia Interactive Services (WIAMIS) held in April 21-23, 2004, at the Instituto Superior Te/spl acute/cnico, Lisboa, Portugal.     

Towards a new generation of transport services adapted to multimedia applications

A partial order and partial reliable connection (POC) is an end-to-end transport connection authorized to deliver objects in an order that can differ from the transmitted one. The service provided by such a connection is also authorized to lose some objects in a controlled manner. The POC approach establishes a conceptual link between connectionless best-effort (CL) and connection-oriented reliable (co) protocols. POC is motivated by heterogeneous CL networks such as Internet which are plagued by unordered delivery of packets and losses, which in turn tax the performances of current protocols. Moreover, it has been shown, that out of order delivery is able to economize the use of network resources such as memory and bandwidth, and reduces end-to-end transit delay. To take advantage of POC’S benefits, applications must be able to relax some transport constraints. In this paper a temporal extension of POC, called TPOC (for temporal POC), is introduced. TPOC offers a conceptual framework, which allows the Qos of distributed multimedia applications to be taken into account. The architecture for offering a TPOC transport service is introduced and evaluated for the transport of MPEG video streams. We demonstrate that POC connections fill not only the conceptual gap between CL protocols (such as UDP) and CO protocols (such as TCP) but also provides demonstrable performances improvements for the transport of multimedia streams such as MPEG video.