Architectural design of adaptive distributed multimedia systems

In the context of a collaborative research project funded by the Canadian Institute for Telecommunications Research (CITR), we have developed a prototype system for remote access to News-on-Demand. This system allows the user to remotely access a multimedia database, containing news clips in the form of multimedia documents, over ATM and other types of networks. Special attention is given to quality of service (QoS) negotiation and adaptation. For instance, a given document may exist in different versions on different sites and possibly corresponding to different presentation qualities, such as video and audio quality, size of display and cast. A graphical interface is available for the user to select his preferences and provides the possibility of obtaining examples of specific quality features. The QoS negotiation and adaptation features allow for the selection of the best configuration for a given user request and for automatic adaptation in case of changes to the system parameters, such as network or server congestion. We present in this paper an abstract architectural design of our adaptive distributed multimedia system for remote access to multimedia databases. This design focused on the aspects of the system which are essential for QoS negotiation and adaptation, which is our main concern in the ongoing CITR research project. The paper gives a functional overview of the system and details its structural and behavioral aspects. An abstract application programming interface (API) is given and issues related to the transition from the abstract system design to an implementation are discussed.