WiFi-RTT Indoor Positioning

Global navigation satellite systems (GNSSs) can deliver very good position estimates under optimum conditions. However, especially in urban and indoor scenarios with severe multipath propagation and blocking of satellites by buildings the accuracy loss can be very large. Using WiFi for indoor positioning is a common approach because WiFi infrastructure is widely deployed. Recently the WiFi IEEE 802.11-2016 standard was released, which includes a fine timing measurement (FTM) protocol, more commonly known as WiFi-round-trip-time (WiFi-RTT) protocol, for WiFi ranging. This paper researches timing based positioning algorithms, in this case using WiFi-RTT distance estimates. Based on two measurement campaigns, in an antenna measurement chamber and in a typical indoor environment, a WiFi-RTT distance error model is derived. Both measurement campaigns show, that the distance is underestimated, hence, the estimated distance is lower than the true distance. The WiFi-RTT distance error model is included in the likelihood function of a particle filter (PF) and the positioning performances is evaluated in an indoor scenario. These evaluations show clearly the possibility of using WiFi-RTT distance estimates for indoor positioning.