A statistical study on the impact of wireless signals´ behavior on location estimation accuracy in 802.11 fingerprinting systems

Much of the recent interest in location estimation systems has focused on 802.11 fingerprinting. Unlike GPS systems, 802.11 based systems can accurately estimate a user´s location inside buildings. Moreover, users don´t need any special equipment to carry around, as their WiFi enabled cell phone can already act as the receiver in WiFi fingerprinting systems. However, wireless access points in buildings are placed mostly according to another criteria, namely to increase the network coverage inside the building. But optimal coverage may not necessarily result in optimal location discovery. In this paper, we provide analyses on data gathered for a real WiFi location estimation system, and show what makes it perform inaccurately in some parts of a building while it is more accurate in other parts. We have defined two new metrics for quantifying the wireless signal behavior of multiple access points in small neighborhoods in a building. Finally, we identify the properties that differentiate well behaving and poorly behaving neighborhoods.