Performance evaluation of a multi-layer location update method

The use of overlapping location areas, so as to introduce a hysteresis effect on the occurrence of location updates, has been proposed by Okasaka et al. (1991) as a means of reducing the amount of location update signaling traffic. In this paper the performance of such a scheme is analyzed in terms of the average time between location updates for a typical user. An urban microcellular environment, with base stations deployed along a rectangular grid is considered, under a Markovian type of user mobility. Two different location area geometries are studied, namely one in which the location areas are diamond-shaped relative to the base stations grid, and another where they are squares with sides parallel to the grid axes. Numerical results are obtained which show that a significant reduction in location update traffic can be achieved. The reduction factor can be on the order of four for location areas of size on the order of 70 cells