Context
Task Description
Mobile computing is a natural further development of distributed computing enabled by wireless networking technologies, portable devices, and means for supporting personal mobility based on, for example, tracking technologies. However, the integration of mobile technologies into stationary distributed systems causes several challenges due to mobile device limitations and changing wireless network connectivity. Many research efforts focus on software adaptations for mobile computer architectures, on fast service discovery, and on lightweight and asynchronous coordination protocols as provided by data space-based technologies. Mobile devices are commonly integrated by means of proxy technologies and lightweight protocols. As mobile computing devices become more and more powerful, integrating these devices as equivalent participants within distributed architectures becomes feasible. This thesis contributes to the research field of mobile computing by proposing a mobility-aware fault-tolerant coordination layer on top of data space-based middleware. Mobility-awareness addresses observation of current wireless link states and prediction of future wireless link states and retention periods based on mobility models. Hence, both reactive and proactive mechanisms can be proposed to tolerate weak network conditions and disconnections by means of local replication of the shared data space. An extensible reference implementation based on the shared object space middleware CORSO demonstrates the feasibility of the approach. For prediction purpose, a second order Markov model for modeling continuous movement in terms of direction and a schedule-centered model based on, for example, a person's calendar entries, are used as reference mobility models. Experiments are carried out to investigate coordination failures caused by moving in a wireless LAN hotspot area and to analyze fault-tolerance mechanisms. Four well known coordination patterns are used as representatives for a manifold of coordination scenarios classified according to the coupling characteristics of processes in terms of time and reference. The results of the experiments are used to investigate possible achievements and inevitable limits of the mobilityaware approach for each coordination pattern.
(2005, finished)
Requirements
Student
Dipl.-Ing. Dr. Karin Anna Hummel (please contact eva Kühn)
Supervisor
Univ. Prof. Dr. Günter Haring (please contact eva Kühn)
A.o. Univ.-Prof. Dr. Dipl.-Ing. eva Kühn (please contact eva Kühn)
