Location Error Spatial Distribution in Urban Wireless Cellular Networks

In this work the spatial distribution of the location error in wireless cellular networks operating in an urban outdoor environment is studied. We assume signal strength based positioning methods that avoid additional network hardware costs and handset modifications, while approaching FCC requirements for emergency positioning. In order to cope with the computational burden associated with the required spatial discrimination of our analysis, we developed an efficient simulator that is capable of analyzing a comprehensive class of cost efficient location algorithms based on the received signal strength measurements made periodically by the mobile terminals in GSM and UMTS systems. The simulation results show that the key factors to achieve positioning accuracy are line-of-sight and homogeneous distribution of base stations in the vicinity of the mobile terminals, leading to the conclusion that the positioning error is location dependent. This conclusion motivates a reliability analysis based on the spatial segmentation of the location process. In the same scenario we estimate the a posteriori location probabilities providing a framework for the further development of reliable methodologies for the tracking of mobile terminals.