Scalability of Wireless Fingerprinting based Indoor Localization Systems

Fingerprinting indoor localization systems have been studied in different perspectives in the past decades; however, a vitally important piece in the puzzle is still missing: how does the system scale with the number of users? In this paper, we present a theoretical study of the issue, where the upper and lower bound of the system's localization reliability with respect to the number of users are derived. Results of our theoretical analysis can be verified by experiments thus can provide meaningful guidance for practical system design, which is in contrast to the scaling-law work utilizing asymptotical analysis that is valid only under unverifiable extreme conditions. The theoretical and experimental results of our work reveal two interesting observations, which shed light on the insight into the scalability of the fingerprinting localization system: First, the localization reliability drops dramatically before the number of users increases to a critical point and then decreases smoothly, where the critical point tends to appear when the number of users equals the number of access points (APs) deployed in the service region; second, even if the number of users approaches to infinity, the fingerprinting localization system still retains certain level of reliability.