Scenario Description – MobVideo

This technical report describes a scenario with a video streaming application, called Mobile Video (MobVideo), designed for a QoS-aware mobile middleware platform. The middleware manages QoS on behalf of the application, by adapting both the application and middleware services to changes in the system context and resource load. The crux of the proposed solution is to let the mobile middleware dynamically choose between alternative application configurations based on their QoS characteristics. Applications are modelled as compositions of services that are explicitly defined by service types. Each service type and alternative implementations of the type is deployed onto the QoS-aware mobile middleware together with a description of the implementations’ QoS characteristics. The scenario serves two objectives. Firstly, it identifies the requirements to a QoS-aware mobile middleware, and secondly, it assist in the validation of concepts and solutions designed into the mobile middleware. In this work not only technical requirements to the mobile middleware are of interest. Engineering methods for modelling services, the environment, and the application QoS characteristics is given equal attention. Without this engineering view, one run the risk of proposing yet another architecture, with a set of mechanisms, that has limited practical value and that do not easily lend itself to existing software engineering methods. The MobVideo application is divided up into components with a clear functional responsibility. The target environment consists of different terminals and communication systems, which creates a problem space with clearly defined system contexts. To be able to perform both signalling and streaming in these system contexts, MobVideo has a design that allow the middleware to alter the component compositions, component parameter configurations, and component implementations. The result is a complex but realistic scenario that ensures that the proposed mobile middleware and modelling methods are useful for other mobile applications that require QoS support from the middleware.