Radio map construction using fingerprints clustering and Voronoi diagram for indoor positioning

Bluetooth low energy (BLE)-based fingerprinting technique has received great attention in indoor localization systems. Despite its significant advantages, the offline site surveys to collect fingerprints to construct a radio map for precise localization in the online phase remain the key challenge because it requires tremendous human effort, time, and cost. To alleviate this issue, this paper presents a novel fingerprint interpolation technique for constructing the radio map based on reference point (RP) clustering and the Voronoi diagram. Firstly, the collected RPs are clustered based on a threshold value of received signal strength difference using the proposed clustering algorithm. A Voronoi diagram is drawn using the centroid of each cluster to partition the clusters in which virtual fingerprints are then generated using the Kriging interpolation algorithm to build a complete radio map. By grouping RPs with similar characteristics in the same region, more accurate virtual fingerprints can be inferred since the RPs in the same region have the tendency to experience similar multipath fading and signal shadowing effects. Experimental results show that the proposed scheme reduces the localization error up to 14% compared to the interpolation without clustering. As a result, we can overcome the site survey issues for IPS by constructing a radio map with more accurate localization results.