An Unsupervised Indoor Localization Method Based on Received Signal Strength (RSS) Measurements

We propose an unsupervised, received signal strength (RSS)- based indoor localization method, which as an infrastructure uses commercial WiFi chipsets and does not require any changes in the existing hardware. The method relies on path loss model for measured RSS levels where path loss coefficient is treated as a discrete random variable which takes values from some finite alphabet. The unknown location and path loss coefficient corresponding to each access point are jointly estimated using the Expectation Maximization (EM) approach. The algorithm is experimentally tested in an office space area of dimensions 32-by-52 m (1600 m²) with only five access points and the achieved average localization error is below 4.5 m.