Joos-Hendrik Böse

An integrated commit protocol for mobile network databases

While traditional fixed-wired network protocols like 2-phase-commit guarantee atomicity, we cannot use them in mobile low bandwidth networks where network partitioning, node failure, and message loss may result in blocking. To deploy traditional database applications easily into a mobile environment, there is a demand for a protocol which guarantees an atomic commit of transactions. This paper introduces a protocol which can guarantee such atomic commitment in mobile environments using a combination of commit and consensus protocols. In addition, it takes advantage of mobile network sub-structures like single-hop environments to reduce message transfer costs.

Robust and fair trading in volatile environments: overcoming technical problems and uncooperativeness

The exchange of electronic information, goods or functionality is an attractive application for mobile ad-hoc networks. However, users will only take part in such systems, if the probability of a successful exchange is high enough. Exchanges may fail either because of communication failures or due to unfair behavior. Both obstacles need to be overcome to achieve a viable system. Existing approaches tend to address one or the other of the problems, ignoring the second one. In contrast, we present an integrated approach and argue that this is more powerful than two isolated solutions. Replicated transaction logs are used to overcome disconnection periods and an evidence-based distributed reputation system is used to encourage fair behavior. The concepts are implemented as middle-ware components and thoroughly evaluated. The evaluation shows that the system is viable in a wide range of realistic settings.

Using Moving Object Databases to Provide Context Information in Mobile Ad-hoc Networks

Applications deployed in mobile peer-to-peer systems have to cope with mobility and fluctuation of nodes. These dynamics restrict the reliability of communication links as well as the availability of certain nodes, services, and resources. Exploring the context of nodes can be used to anticipate these shortages. Context-awareness enables improvement of performance of systems and enables adaptation of applications in order to make their behavior more relevant with respect to their current situation. Preevaluation of context can be used to estimate future availability of crucial resources and reliability of communication links. Which information is considered to be relevant context information varies according to the application scenario. In this paper, we present a model for context information along with a mobile service that provides a local view of surrounding nodes in a Mobile Ad-hoc NETwork (MANET). The service is designed to enable efficient prediction of future stability of the vicinity of a node.

Reliability evaluation of group service providers in mobile ad-hoc networks

A main challenge for applications in mobile ad-hoc networks (MANETs) is to survive link and node failures One approach to overcome volatility of MANETs is to evaluate the reliability of communication peers allowing to choose the most reliable instances and to estimate the risk of failure before using a remote service We present an approach that integrates discovery and reliability evaluation of group service providers A group service provider is a node providing a service which is used by a group of nodes simultaneously.