Subway station real-time indoor positioning system for cell phones

As wireless local area network, WLAN, access point (AP) are becoming very common wireless communication infrastructures in indoor environments, Wi-Fi signal based Indoor Positioning Systems (IPS) have been widely developed in recent years and one of the most popular technologies is the received signal strength (RSS) fingerprinting technology. However, due to large amount of time-consuming work required for offline calibration in large indoor environments, researchers have investigated generating the calibration database while walking about instead of carrying out measurements over a time period at fixed reference points [1]. This paper combines both Wi-Fi fingerprinting and Pedestrian Dead-reckoning (PDR) technologies to introduce a real-time indoor navigation system for large complex three-dimensional indoor environments including a novel calibration method with associated novel matching algorithms. Detailed experiments were conducted in two subway stations with complicated structure under normal operating conditions in which trains regularly arrived and departed and groups of people walked to and from the trains. The results for real cell phone tracking on phones carried by passengers, give a satisfactory error of 2.9 metres during peak congestion times and 1.7 metres when few people were in the station.