Abstract: A system for locating a wireless device involves the use of the measured signal strength of various base stations in the building or outdoor area under analysis. A topological map of the building or outdoor area under analysis is created. The map is divided into cells, and signal intensities are collected in each cell. For each cell, the signal from a particular base station is fit to a statistical distribution, such as a Gaussian distribution, and the parameters of the statistical distribution are estimated. After a device obtains a set of signal strength measurements, a probabilistic technique is employed to estimate the probability of the existence of the measurements in each of the cells of the building or area under analysis. The estimated location is the cell with the highest probability. A mobile user is tracked with the use of a Markov chain and the system can be calibrated to account for equipment and environmental variations.