Architecture of a large scale location service

Many mobile applications require some knowledge about the current geographic locations of the mobile objects involved. Therefore, services exist that can store and retrieve the position of mobile objects in an efficient and scalable way. More advanced location-aware applications, however, require additional functionality, like determining all mobile objects inside a certain geographic area (range query). This functionality is not supported by existing services on a large scale yet. In this paper, we present a generic large-scale location service. We describe the location service model, defining the semantics of position, range and nearest neighbor queries. A hierarchical distributed architecture is presented, which can efficiently process these queries, and the structure of a main-memory database for efficiently storing and retrieving position information on a location server. Finally, through measurements on a first prototype of this architecture, we show the feasibility of such a location service

A comparison of protocols for updating location information

The detailed location information of mobile objects, for example that of a user with a mobile computer or phone, is an important input for many location-aware applications. However, constantly updating the location information for thousands of mobile objects is not feasible. Update protocols for location information therefore use the special properties of this information to transmit it as efficiently as possible, that is requiring only few update messages, while still being effective in returning the location information with the desired accuracy. Different classes of such update protocols are described in this paper and a new combined protocol is proposed. To be able to compare their effectiveness and efficiency, we present an analysis for the minimum and average resulting accuracy of the location information on the receiver and the number of messages transmitted between them. We also present some simulation results, which we have performed to back up our analysis

Abschlußbericht der Projektgruppe Evolutionäre Algorithmen

Viele in der Praxis interessante Optimierungsrobleme sind NP-hart. Da kein Algorithmus bekannt ist, der ein Optimum für solche Probleme mit geringerem als exponentiellem Aufwand findet, sucht man, ein Optimum mit Heuristiken möglicht gut anzunähern. Zu diesen gehören auch die Evolutionären Algorithmen. Ziel der Projektgruppe EVA war die Entwicklung einer Experimentierplattform für Evolutionäre Algorithmen, die die Implementierung und empirische Untersuchung dieser Algorithmen erleichtert. Besonderer Wert wurde daher auf möglichst große Unabhängigkeit der Algorithmen vom Problem gelegt. Der Endbericht der Projektgruppe enthält nach einer Einführung den Entwurf von GENOM, die Beschreibung der Implementierung sowie Hinweise zur Bedienung und zu Erweiterungsmöglichkeiten

A map-based dead reckoning protocol for updating location information

An important aspect of location-aware services is the management of location information. To this end, location information needs to be transferred from a mobile device, which determines this information by means of a local positioning sensor (such as GPS), to a location service, where the location information can be queried by applications. Because bandwidth in wide area mobile communications is still scarce and expensive, it is important to use an update protocol that requires as few messages as possible while still guaranteeing a desired accuracy of the location information. To decrease the number of necessary update messages, so-called dead-reckoning strategies have been proposed. In this paper we give an overview of different variants of dead-reckoning protocols for updating location information and propose a new map-based protocol. While a simple dead-reckoning protocol already reduces the number of update messages by up to 83, the map-based protocol further reduces their number by again up to 60

Analysis of distribution schemes for the management of location information

New applications in the area of mobile computing make heavy use of knowledge about the application's run-time environment. Applications running on mobile devices in particular exploit knowledge about their current geographical position or query for the location of other interesting objects. To manage such queries some applications provide a location service specifically tailored for their needs. The efficient and application-independent handling of such queries calls for a global and universal location service. Considering a large number of users and queries to be handled, a distributed implementation of a location service is necessary. This paper analyses three schemes for the partitioning of location information and derives a performance model for these partitioning schemes. Finally, an example for the application of the analysis' results is presented for a universal location service within the Nexus system, an infrastructure for location aware mobile computing

Nexus - an open global infrastructure for spatial-aware applications

Due to the lack of a generic platform for location- and spatial-aware systems, many basic services have to be reimplemented in each application that uses spatial-awareness. A cooperation among different applications is also difficult to achieve without a common platform. In this paper we present a platform that solves these problems. It provides an infrastructure that is based on computer models of regions of the physical world, which are augmented by virtual objects. We show how virtual objects make the integration of existing information systems and services in spatial-aware systems easier. Furthermore, our platform supports interactions between the computer models and the real world and integrates single models in a global 'Augmented World'

POSITIONING AND LOCATION SERVICES FOR INDOOR AREAS IN NEXUS

The research project „NEXUS “ is currently being carried out within

Nexus - An Open Global Infrastructure for Spatial-Aware Applications

Due to the lack of a generic platform for location- and spatial-aware systems, many basic services have to be reimplemented in each application that uses spatial-awareness. A cooperation among different applications is also difficult to achieve without a common platform. In this paper we present a platform that solves these problems. It provides an infrastructure that is based on computer models of regions of the physical world, which are augmented by virtual objects. We show how virtual objects make the integration of existing information systems and services in spatial-aware systems easier. Furthermore, our platform supports interactions between the computer models and the real world and integrates single models in a global "Augmented World". Contents 1 Introduction 3 2 General Idea 4 2.1 Augmented Areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2 Augmented World . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3 Example Scenario 6 4 Require..