Raf Hens

Adaptive Online Deployment for Resource Constrained Mobile Smart Clients

Nowadays mobile devices are more and more used as a platform for applications. Contrary to prior generation handheld devices configured with a predefined set of applications, today leading edge devices provide a platform for flexible and customized application deployment. However, these applications have to deal with the limitations (e.g. CPU speed, memory) of these mobile devices and thus cannot handle complex tasks. In order to cope with the handheld limitations and the ever changing device context (e.g. network connections, remaining battery time, etc.) we present a middleware solution that dynamically offloads parts of the software to the most appropriate server. Without a priori knowledge of the application, the optimal deployment is calculated, that lowers the cpu usage at the mobile client, whilst keeping the used bandwidth minimal. The information needed to calculate this optimum is gathered on the fly from runtime information. Experimental results show that the proposed solution enables effective execution of complex applications in a constrained environment. Moreover, we demonstrate that the overhead from the middleware components is below 2%.

Design of a multimedia gateway for mobile devices

Although mobile users are currently offered a lot more capabilities on their mobile devices, they still experience some limitations. They can surf the Internet, read their e-mail and receive MMS messages, but they have limited processing power, storage capacity and bandwidth and are limited in their access to peripherals (e.g. printers). We have designed and implemented a multimedia gateway for mobile devices that reduces these limitations. It gives the mobile devices transparent access to high capacity devices connected to the gateway, which is built around a central, modularly extensible server that can run on any PC or home gateway. It manages two sets of modules: one set offering the actual services and another set handling the IP-based wireless interaction with the client applications on the mobile devices. These modules can be added and removed dynamically, offering new services on the fly. Currently services for storage, printing, domotics and playing music are provided. Others can easily be added later on. This paper discusses the architecture and development, the management of modules, the actual services and their benefits. Besides a proprietary implementation, it also looks into OSGi and how both platforms compare to each other, concerning design, architecture, ease of development, functionality, ...

Runtime Deployment Adaptation for Resource Constrained Devices

This paper proposes a solution for the resource constraints of mobile devices. As an alternative for the thin client approach, a hybrid approach is presented, that is able to adapt dynamically to changes in the context in which the mobile application runs. By switching dynamically, at runtime, between local and remote execution of components of an application, the quality of experience of the end user is optimized. An ILP model to minimize the impact on end user experience, taking into account different context parameters, such network delay and available processing resources, is presented. Tests performed with this model have resulted in a simplified ILP model. The behaviour of this model under changing network conditions is presented. Finally, the possibilities to incorporate this model into an earlier designed framework are discussed.

Adaptation Strategies for Performance Failure Avoindance

Nowadays, technologies are providing the mobile terminals with much more powerful computational abilities. Such improvement made it possible to run many complex applications on mobile devices. However, many of these new applications are also resources demanding. Lacking sufficient resources would cause performance failures and impact negatively on the users’ quality of experience. In order to improve this, it is important to provide the users with an easy access to specify their requirements. It is also crucial to monitor the system resources and make corresponding adaptation immediately according to the user’s specifications. In this paper, we propose adaptation strategies that flexibly combine the process of monitoring and adaptation, and provide an easy way to specify user’s requirements. By tuning the quality of service, we reduce the applications’ demand on system resources, thus decreases the chances of performance failures and improving the users’ quality of experience.