A cell-based distributed location management protocol for cell-hopping networks

We consider the problem of location management in cell-hopping networks, where the only infrastructure for routing and switching user data is a set of ad-hoc base stations owned by small individual operators. Such networks do not have a reliable fixed infrastructure to host central or distributed location register databases. We propose a novel location management protocol, which obviates the need for a location register database. The location of a mobile node can be determined by a simple two step process. The originating base station first broadcasts a location query message to all base stations in the area, and the base station serving the mobile terminal in question responds to the originating base station with a unicast reply message. We obtain the mean locating time as a function of coverage area for a hexagonal cellular topology through an approximate analysis, which remains within 5% of exact solutions for large coverage areas. Our analysis reveals that locating time increases more slowly than linearly as a function of coverage area. We also conduct a discrete event simulation of a 7-cell hexagonal topology with pedestrian, suburban driving, and highway driving mobility patterns. A close match between simulation and analytical results confirms the validity of our analysis. Simulation results also confirm our intuition that the speed of a mobile node has no impact on locating time, but higher speed slightly increases the probability of not finding a mobile node in the destination cell, even after a successful location resolution (misrouting).