Internet applications nowadays are part of our everyday life. Gathering information from any networked site in the world, exchanging documents, transferring information via e-mail, telephone and video conferencing, e-learning or Web shopping are well known examples for Internet collaboration. The common characteristic of all these activities is the elimination of the spatial distance between involved partners. Furthermore, the information can be accessed with different devices, from hardwired PCs via WLAN-capable notebooks and PDAs (Watters, 2003) to mobile phones. The introduction of wireless communication in recent years opened new opportunities for collaboration based on so called location-based services (Schiller, 2004; Jagoe, 2003). These benefit from the fact that the most wireless devices need a dedicated access point to connect to the network. This access point registers all users in the neighborhood, and thus adds new information relevant for communication: the current spatial position of the device and its user. All registered users/devices create a local neighborhood for ad-hoc communication. This scenario is very common in our everyday life: People contact other people at different locations and start a conversation. Furthermore, they often share documents to learn (e.g., lecture slides), for entertainment (e.g., holiday photos) or¾most common¾to collaborate and to develop products in a team. All this is possible in the Internet, too, and countless applications were developed in recent years. However, each user has to know the persons to be contacted a-priori and have the access information available¾for example, e-mail address or ICQ number¾before the first contact. In opposite, users in the local neighborhood can approach other members without knowing each other a-priori. The partners must declare their willingness for communication; for example, by installing a client program and setting the security parameters accordingly. In summary, the restriction to a local neighborhood or the consideration of the current location is opposite to the main design idea of the internet to bridge the gap between spatially divided users and resources. However, this approach aims to satisfy human needs to learn more about their current local environment, the infrastructure and the people in the near neighborhood. Therefore, peer-to-peer-based collaboration platforms allow a location-based selection of relevant information and ad-hoc communication with users in the range of the current access point.

The steady rise of mobile computing devices and wireless local-area networks (WLAN) has fostered a growing interest in location-aware systems and services (LBS). Context-awareness in mobile systems give users more convenience with services specific to their preferences, behaviour and physical position. This paper presents an architecture for LBSs in WLANs describing the essential location determination component. An example service using Web Service techniques is described to illustrate efficient service invocation and interaction.

The steady rise of mobile computing devices and wireless local-area networks (WLAN) has fostered a growing interest in locationaware systems and services (LBS). Mobile systems using loosely coupled services in a service-oriented architecture (SOA) can give users more convenience with services specific to their preferences, behaviour and local environment. In this work we presents a SOA for LBSs in WLANs. The location determination component and the functional and structural features of the architecture are described. An example service using Web service techniques illustrates the efficient service invocation and interac-

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In this paper we present multimedia services for a collaborative work environment in wireless networks. This environment supports a location-aware communication in a neighbourhood defined by a given access point. All participants of this spontaneous virtual community can ad-hoc – without any previous exchange of contact information – interact via different multimedia services such as messaging, audio/video conferencing, filesharing, etc. Users can join the community as soon as they enter the network zone around the access point or leave it at any time without affecting the communication platform. For the user interaction a general protocol is used, which can be adapted to various application types. A description of two sample applications – video conferencing and shared whiteboard – for this location-aware environment

This paper describes a flexible, modular system for processing of multimedia information acquired with mobile devices. The workflow is described using a sample scenario where a user takes a photo with an MMS-capable cell phone, sends it to a corresponding service for face identification, and receives the meta-information via SMS as a response. The main component in this chain is a gateway, which offers interfaces for different networking technologies on the one side and interfaces for various multimedia services on the other side. The design of the gateway considers the fast development of mobile technology by implementing the architecture as open as possible.

Many current applications for wireless networks are based on a static infrastructure and only operate within the range of access points to a wired network. The inflexibility of these hierarchical solutions yields problems like bottlenecks, limited scalability and congestions. In this paper we present the routing technique Stigmergy based on swarm-intelligence to share resources in wireless ad hoc networks. We present a simulation platform for Stigmergy which provides resource sharing where n resource requestors relate to m resource providers, with n,m ⩾ 1. It routes messages between one of the n resource requesting nodes and one of the m resource providing nodes.

The main research in the area of image databases addresses the improvement of retrieval quality and the speedup of the query processing. A number of image retrieval systems reached meanwhile a level, where these are used in real-world applications and thus create new demands. In particular dealing with a large, simultaneous number of users and queries requires concepts for resource management, which strongly consider the underlying architecture and the various approaches for image retrieval. This paper is our first step in this direction, as it provides a formal problem specification and a proof that this problem is NP-hard.

During the last years considerable effort has been put into developing scheduling and load balancing techniques and models for the processing of tasks in parallel and distributed systems. In this paper we extend an existing scheduling model called the divisible task model to adapt it to cluster architectures and make it applicable to a broader class of applications. To achieve this we present two new modifications which allows recursive modelling and will increase the models flexibility and performance. The goal of this work is to reduce the data volume which has to be transfered over the communication links to get an equally balanced load on the nodes of the system. As test-system we use a cluster-based image retrieval system to check the achieved performance.

During the last years considerable effort has been put into developing scheduling and load balancing techniques and models for the processing of tasks in parallel and distributed systems. In this paper we extend an existing scheduling model called the divisible task model to make it applicable to a broader class of practical applications. To achieve this we present two new modifications to give the model a greater flexibility and to increase its performance. The goal of this work is to reduce the transfer volume over the communication links and getting an equally balanced load on the nodes of the system. As test-system we use a cluster-based image database to check the achieved performance.

The steady rise of mobile computing devices and local-area wireless networks has fostered a growing interest in location-aware systems and services. Local services will be one of the most exiting features of the next generation wireless systems. This paper gives an overview of the main concerns of location-based services (LBS) which are already established in the area of mobile phone networks. Transferring LBS to an indoor wireless network, especially WLAN, is the next step. As a first step for any kind of LBS a positioning system is required. Different techniques exist in all major wireless networks which have basic procedures in common. This paper presents, analyses and categorises state-of-the-art techniques for indoor positioning and examines the suitability to support LBS in WLANs.