Positioning based on received signal strengths from base stations is highly sensitive to the effects of signal attenuation, reflection, and scattering. Moreover, experimental measurements show that received signal strengths fluctuate significantly over time due to noise and interference. Unlike most of the related work our approach does not rely on the presence of a priori information about base station positions, objects influencing radio signal propagation, and signal propagation characteristics. Instead of trying to compute the current position defined by coordinates, the goal of our system is to infer a user?s present logical position. In addition, our system particularly differs from previous work in the chosen statistical approach, which explicitly copes with signal strength fluctuation over time and allows control over system accuracy by means of specification of confidence intervals.