Locating Objects in Mobile Computing

In current distributed systems, the notion of mobility is emerging in many forms and applications. Mobility arises naturally in wireless mobile computing, since the location of users changes as they move. Besides mobility in wireless computing, software mobile agents are another popular form of moving objects. Locating objects, e.g., identifying their current location, is central to mobile computing. In our research, we address issues in storing, querying, and updating the location of moving objects.
To accommodate the increase in user population in future personal communication systems, hierarchical architectures of location databases have been proposed. A scheme based on forwarding pointers is presented, that reduces the cost of network and database traffic generated by frequent location updates in such hierarchical architectures. To avoid the building up of long chains of forwarding pointers, various purging strategies are introduced. We comparatively study the communication and database cost of the non forwarding and of the forwarding schemes along with a set of different purging strategies for a range of call to mobility ratios and for users with different moving and calling behaviors. An adaptive scheme is then proposed that takes advantage of these studies. Finally, we investigate consistency issues that arise when performing updates and lookups at the various levels of the distributed location database and for the case of concurrent arrivals of call and move requests.

Related Reports

An Efficient Hierarchical Scheme for Locating Highly Mobile Users,
with I. Fudos. Proceedings of the 6th ACM International Conference on Information and Knowledge Management (CIKM98), November 1998. To appear.
Tracking Mobile Users Using Hierarchical Location Databases
with I. Fudos. Technical Report 97-2, Computer Science Department, University of Ioannina, Greece. February 1997. Also in the Proc. of the 6th Panhellinic Conference on Informatics , Nov. 1997.
Locating Moving Objects (In Greek)
Slides from a short talk I gave at the National Documentation Centre, May 1998.
Locating Objects in Mobile Computing.
with G. Samaras. Submitted for journal publication. Also available as Technical Report 98-20, Computer Science Department, University of Ioannina, Greece, 1998.