FOKUS Publikationen 2006

Abstract â There are two important trends that seem to be the driving forces in the evolution of communication networks. On the one hand, mobility support becomes a âmustâ for emerging services and technologies. On the other hand, services tend to have a ubiquitous nature, they are based on intelligent devices being embedded in the ambient environment surroundig us. These new trends result in new research challenges as well. In this paper we first present the specificities of wireless ad-hoc and sensor networks, technologies that were developed to support these new requirements. Then, we highlight the most important and most challenging issues that arise from these specificities.

There are two important trends that seem to be the driving forces in the evolution of communication networks. On the one hand, mobility support becomes a âmustâ for emerging services and technologies. On the other hand, services tend to have a ubiquitous nature, they are based on intelligent devices being embedded in the ambient environment surroundig us. These new trends result in new research challenges as well. In this paper we first present the specificities of wireless ad-hoc and sensor networks, technologies that were developed to support these new requirements. Then, we highlight the most important and most challenging issues that arise from these specificities. 1.

The need to count on trusted systems is growing day by day. Together with traditional domains such as medical devices, automotive, railway, aeronautical, space and telecommunications, new applications and services are coming up everyday. Terms such as ubiquitous, pervasive, or autonomic computing, products under the general umbrella of smart devices or the use of large wireless sensors networks indicate a clear trend in the increase of application complexity and dependency. Our daily life dependability on computers and computer systems is growing at a high rate, and validation is gaining importance at the same rate. To perform a proper validation process encounters a number of problems both from a technical and from a managerial point of view, also considering that the complexity of the underlying software is growing as well. As a consequence inputs from research contributions and experience from industry are required in order to enable innovative, and often more rigorous,approaches. The System Testing and Validation Workshop is a series of events initiated in the year 2002 and seeks to provide answers to the many open issues related to validation.

In order to get high-quality software systems high-quality models are needed. Modelling rules and design guidelines can help to improve the quality of a model. This paper presents a flexible solution for phrasing and evaluating modelling rules and design guidelines for models by using the Object Constraint Language as the target environment to achieve a higher quality of models. The presented solution is based on Open Source tools like OSLO and describes how it is applied in an automotive domain.

Model Driven Architecture (MDA) introduces a new trend in the software engineering world which enable automatic code generation from abstract models. We believe, that MDA can also be used for test generation process. The UML 2.0 Testing Profile (U2TP) is a test specification based on the UML 2.0 standard. It enables test specification and it is capable of inter-operating with the existing test technologies for black-box testing. This paper provides a solution for a graphical implementation of U2TP specification and a method for storing the created models in a persistent repository. The solution is part of a tool chain for automatic generation of executable tests.

Developing telecommunication applications has evolved from the using closed service architectures as is the case in Intelligent Networks (IN) towards open distributed service architecture such OSA/Parlay, and the Open Mobile Alliance (OMA). The Open Mobile Alliance (OMA) specifies different standardized components called enablers to create an environment in which services could be developed and deployed. Therefore, OMA provides a service-oriented architecture (SOA) and enables the mapping of service elements onto the underlying network infrastructure components [1]. On the other hand, the approach used in MobiLife[2] is more user-centric and tries to bring advances in mobile applications and services within the reach of users in their everyday life by innovating and deploying new applications [2]. Consequently, the MobiLife paradigm also follows a high-level service-oriented approach quite similar to the OMA approach. Issues such as extensibility, scalability, and flexibility are quite critical in determining the success of a certain service. When using the last mentioned approach, service composition on top of OMA enablers or on top of the MobiLife framework is greatly facilitated. The focus of our paper is on the significant differences between the classical black box approach and the modular approach used by the OMA and MobiLife for building telecommunication services on the top of the IP Multimedia Subsystem (IMS) [4] architecture.

Low earth orbit (LEO) satellite systems gained considerable interest towards the end of the previous decade owing to some of their appealing features, such as low propagation delay, global coverage and their ability to communicate with handheld terminals. However, one of the main factors that degrade the quality of the provided services is the handover of a call between contiguous cells or satellites. In this paper, we propose and evaluate an inter-satellite handover technique for multimedia LEO satellite systems with overlapping coverage areas among their satellites. The proposed scheme relies upon the queuing of handover requests in order to achieve low dropping probabilities. Moreover, the main mechanism behind the proposed scheme that allows it to attain an enhanced perform ance is based on dynamic bandwidth deallocation. According to the proposed mechanism capacity reservation requests are canceled when the capacity that they strive to reserve is unlikely to be used. The good characteristics of the proposed scheme were confirmed via simulations, where significant gains in the performance were witnessed for all the scenarios examined.

This paper describes an IPTV solution provided by mobile operators. This approach is based on the IP Multimedia Subsystem (IMS) which is used for controlling and charging the offered services. The architecture provided here is generic in the sense that various access technologies can be used to acquire the IPTV services. To validate our IPTV solution, a prototype using XDSL as an access technology is implemented. This prototype is a part of the ongoing development of the proposed architecture.