next up previous
Next: Parallel and Distributed Debugging Up: Description of Research Projects Previous: WWW Browsing over a Wireless Link

Location Management in Cellular Systems

Cellular systems such as GSM need to keep track of the location of a mobile subscriber to route incoming connection establishment requests. The solution proposed in the GSM standard statically partitions the cell layout into location areas and keeps track of location at this level of granularity. The same tiling of location areas is applied to all mobile subscribers, and location update traffic is confined to border cells of a location area. We believe that mobile subscribers show clearly identifiable patterns of mobility and proposed a location management scheme that utilizes individual mobility patterns to reduce location update and paging messages. To implement our algorithm, only a few kBytes of additional memory and very little processing on the SIM (subscriber identity module) are required to build and maintain the user profile. Also, the VLR (visitor location register) needs to store a list of cells comprising the personal location area, instead of a simple location area identifier. Using statistical data collected by the Region of Waterloo for traffic planning purposes, we developed a subscriber mobility model, implemented a simulation, and compared our algorithm to a number of variants of the GSM location management algorithm. The results show that our proposal outperforms the static location management algorithms in terms of location update and paging costs. It also spreads the location update traffic more evenly across the network cells. A number of papers describing the mobility model and the results of our simulation are currently under preparation.

Thomas Kunz
Department of Computer Science
University of Waterloo
Waterloo, Ontario N2L 3G1
Fri May 2 10:11:04 EDT 1997