Ulf Wehling

Spaces-A Replication Scheme for Sharing Tagged Files in Hybrid Wireless Networks

Spaces is a replication scheme for sharing files enriched with meta-information in hybrid wireless networks. It relies on existing standards and prevalent technologies. Realized as a URI scheme, spaces allow a seamless integration with current systems in a platform-independent manner. Feeds are used as a basis to exchange data among subscribers to the Space, both within local groups in a self-organizing fashion as well as from the Internet, depending on connectivity. Tagging is employed, enabling to label and quickly identify relevant content. Additional meta-information is used in order to allow resolving files residing in the Space locally, independently of their physical location.

ArCoMo-An Artefact-based Collaborative Mobile Learning Environment

In this paper we propose Arcomo, a mobile learning environment designed for hybrid wireless networks. We introduce three key concepts used in the environment: spaces, anchor points, and artefacts. Spaces are used to uniquely identify, store, share, and disseminate learning materials, annotations, and examples among mobile users. Anchor points are defined by users on documents in spaces. Every anchor point specifies a location in a document, which can be a word, a sentence, a paragraph, an image, or even the whole document. Artefacts are utilized to describe relationships between anchor points together with comments on them. This way, they can map the current working context of a student that typically contains several open documents and a relationship between them. The main contribution is a general annotation concept which supports different file formats and is applicable for collaborative mobile users.

UbiSettlers--A Dynamically Adapting Mobile P2P Multiplayer Game for Hybrid Networks

UbiSettlers is a prototype of a mobile multiplayer game for hybrid networks running on real hardware. It uses dynamic adaptation and topology control mechanisms to deal with problems inherent to ad hoc and wireless infrastructured networks. In particular, a globally consistent view on the games state is not mandatory. This is facilitated by resolving inconsistencies through appropriate integration into the semantics of the game itself. In addition to that, we focus also on network feedback to integrate changing network topologies into the game. Moreover, stimulating cooperation is another major facet of the game design and implementation

Efficient Topic-Based File Sharing in Hybrid Wireless Networks

File sharing is an essential daily task. This includes for instance the sharing of pictures, music, and learning material. Commonole sharing applications, however, are not suitable for mobile networks as the induced network load is too high. In this paper a prototypically implemented topicbasedole sharing application for hybrid wireless networks is presented and evaluated. For the evaluation of the application, two different information dissemination mechanisms for mobile networks are introduced and compared against each other. Theorst one is based on a peer-to-peer (P2P) communication approachbetween localone-hopneighbors. The second one employs a clustering algorithm for mobile networks in order to reduce the produced network trafoc.

Improving the Bandwidth Consumption of File Sharing in Mobile Networks through Clustering

Mobile devices, such as laptops, smartphones, and PDAs are nowadays widely used. One essential daily task, among others, is the sharing of files, e.g. podcasts, pictures, or learning material, with others. The dynamic nature of mobile networks, together with the limited bandwidth, make common file sharing protocols unsuitable for such dynamic environments. In this paper two different strategies for the dissemination of files in mobile networks are introduced. Both approaches are evaluated based on different criteria, such as the file size and the level of interest. The first strategy is based on the en-passant communication pattern, which is a peer-to-peer approach between local one-hop neighbors. The second approach employs a clustering algorithm for mobile networks.