Indoor positioning based on hybrid algorithms: Wi-Fi fingerprint and ranging

This paper focuses on the implementation problems for indoor positioning system, whose main process includes building fingerprint database, ranging and matching online. During the construction of a fingerprint map, signal characteristics are collected at known positions or reference points in a building. While in the ranging and online phase, mobile device application scans access points around and selects two access points from which received signal strengths are stronger, then we convert the signal strengths into a rectangular region where the user is surely inside it. Meanwhile, the current fingerprint probability distributions are compared with the offline radio fingerprint map. The user´s location is estimated by calculating the smallest Bhattacharyya distance in the above-mentioned rectangular region. Experiments show that our method by means of parameter optimizing reaches a median error of 2.82m, which is superior to the median error of 3.4m by traditional Wi-Fi fingerprint.