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< Contents ERCIM News No. 54, July 2003
SPECIAL THEME: Applications and Service Platforms for the Mobile User

Towards a Virtual Home Environment Application Server

by Ali Hafezi and Klaus-Peter Eckert

A Virtual Home Environment (VHE) is a means for the context-dependent provision of telecommunication-related services to nomadic users. The Fraunhofer institute FOKUS has participated in several national and international projects that have defined VHE architectures and implemented appropriate platforms. While the current work focuses on the personalisation and adaptation of services, future work will concentrate on operational aspects of VHE systems including the flexible deployment of services, comparable to the deployment of components in a supporting application server.

The future success of wireless networks like UMTS and WLAN depends on the large availability of innovative services. Such services will drive network usage up for data and voice services and will hopefully make network technologies like UMTS worthwhile over the long term. So far the services provided by a particular operator have been strongly tied to the particular capabilities of the operator’s network vendor. This vertical approach to service provisioning undermines innovation; services are excluded from specialised service developers because the services typically have to run in a proprietary execution environment. In the last few years there has been considerable worldwide turmoil in the area of communication service development and deployment, leading to different service architectures, different interfaces and different service environments. On the other hand, the third-generation mobile networks are currently under intensive study by international standardisation bodies such as the ITU and ETSI, as well as the European Commission. Where possible, Fraunhofer FOKUS has tried to merge these resulting architectural and network concepts in order to provide a global service-provisioning architecture, coming from the different solutions and capabilities suggested and provided by various projects.

Starting from TINA-C’s service architecture and appropriate inter-domain reference points, Fraunhofer FOKUS has developed a series of service execution environments. These provide well-defined interfaces between services and execution environments on the one hand, and between execution environments operated by different providers on the other. One lesson learned was that it is very hard to agree on a global standard for the interfaces between services and their execution environment. Thus every execution environment defines its own internal interfaces to services. These interfaces become more and more complex when the execution environment provides VHE support. Additional interfaces between the service and adaptation and profile components have to be introduced. Appropriate topics have been investigated in a series of VHE-related projects like Vesper, AlbatrOSS or VHE-UD.

A new category of problems arises in the case of mobile, nomadic users. These users need personalised access to their services even if they connect from other network or VHE providers. In such situations, either interworking is necessary between service instances running in the home and visited provider’s domain, or cross-domain access to profile information is required. These scenarios are investigated in the AlbatrOSS project. Again the lack of globally standardised interfaces between services and execution environments prevents the provision of a comprehensive solution.

One possible solution to these kinds of problems is the introduction of service deployment descriptors that describe the requirements and obligations of services towards their users and execution environments. As in well-known component technologies like EJB or CCM, the services as well as the execution environments describe their required and provided interfaces and the appropriate protocols. Thus it is possible to map both descriptions either manually or automatically and to generate bridging components that adapt the technology and protocols between services and execution environments. First steps in this direction have been made in the VHE-UD project.

This adaptation during the deployment time of a service needs only static information. It can be used to satisfy service-level agreements and to guarantee some agreed quality of service during the start-up phase of a service. Much more complex is the task of controlling and justifying the quality of service during the execution time of the service. Components are required that monitor the status of the network and of the services, the end-to-end evaluation of the provided service quality is necessary and an appropriate end-to-end reconfiguration of the service must be enabled. In a fully operational environment, the monitored status information will also be used for logging and accounting purposes.

In current projects, Fraunhofer FOKUS has developed various building blocks for a comprehensive VHE platform together with a series of component-based, adaptive middleware environments. It will be the challenge of future projects to integrate these ideas, experiences, and software modules into a global VHE architecture built around the concept of VHE application servers.

Please contact:
Ali Hafezi, Fraunhofer FOKUS
Tel: +49 30 3463 7109