Method for efficiently constructing and updating radio map of fingerprint positioning

Location fingerprinting for outdoor areas using existing wireless local area network infrastructure is growing rapidly in importance and gains commercial interests in location-based services. The most challenge in outdoor fingerprint positioning is the fluctuation of received signal strength (RSS). In the paper, we propose a micro-cell-based radio map construction method targeted to deal with the unstable RSS and build a metropolitan-scale radio map efficiently by using spatial diversity instead of temporal diversity and an average filter which are made use of by the conventional methods of building radio map. The paper also presents a self-adaptive update algorithm using RSSs which are collected by users of Wireless-LAN (WLAN) location system and the estimated user's location to update the radio map, which further improves the positioning accuracy. Experimental results in outdoor WLAN environments demonstrate that our methods not only improve the efficiency of constructing the radio map but also the positioning accuracy.