Accuracy Investigations of Fingerprint-based Indoor Localization System Using IEEE 802.15.4 in Two-Floor Environment

Currently, we are studying the fingerprint-based indoor localization system using IEEE 802.15.4 (FILS15.4) as a user-friendly, low-cost, and highly reliable system. A user carries a small light transmitter running with a coin battery. By comparing the link quality indicator (LQI) of the transmitted signal at multiple receivers in the field to the fingerprint of every room, the system is able to detect users' locations. However, the localization accuracy has been evaluated only on single floors of a building. In this paper, we investigate the localization accuracy of FILS15.4 on two floors of #2 Engineering Building at Okayama University as a more practical environment. Since a receiver can often detect the signal from a transmitter on the adjacent floor, the LQI values at the receivers on both floors should be used together. Using the FILS15.4 testbed system, we conducted the experiments under three cases of fingerprints using five and six receivers and confirmed that the five receivers allocated on both floors could achieve sufficiently high accuracy by 97.7%.