Indoor localization with UMTS compared to WLAN

The objective of this paper is to compare the accuracy in location estimation which can be achieved in an indoor-scenario for WLAN and UMTS using RF-Fingerprinting with various metrics and distance norms. The measurements were done in a 20 m × 15 m office environment, using 4 3G Small Cells (Home NodeB) and 4 WLAN-APs. To create the radio map, fingerprints were taken within a grid of one meter. For location estimation a deterministic approach using Euclidean Distance norm with a WKNN algorithm was used based on RSS and AP-visibility as metrics. As a probabilistic approach a histogram comparison method has been applied using Kullback-Leibler-Divergence as a distance norm. It can be shown, that the accuracy in Indoor-RFFingerprinting with UMTS is comparable to the accuracy, which can be achieved in a similar WLAN-Testbed. Signal visibility is an alternative metric to RSS for interference limited systems, such as UMTS. As a conclusion UMTS Small Cells are an interesting alternative to WLAN for indoor RF-Fingerprinting, especially because the same hardware can be used for traffic and for localization purposes, since the pilot is not subjected to adaptive frequency hopping or power control, as it is the case in most WLAN installations for interference reduction.