Sensor Measurements for Wi-Fi Location with Emphasis on Time-of-Arrival Ranging

Wireless local area network (WLAN) location is the perfect complement to global positioning system (GPS) receivers for providing users with location information. WLAN operates in many areas in which GPS receivers cannot establish a lock, such as in indoor environments and metropolitan (obstruction by tall buildings) areas. There are many references to WLAN location in scientific literature. Most of this literature concentrates on signal-strength-based approaches. The advantage of signal strength approaches is that they are easy to implement, usually only requiring software modifications. In this paper, we discuss a novel time of arrival (TOA) approach that Intel research has developed. Although this approach typically requires minor silicon or firmware modifications to implement, it can deliver significant performance improvements over signal-strength-based measurements, as shown in this paper. Currently, Intel is introducing this method as an approach to add fine-accuracy location into the IEEE WLAN standard, 802.11 v.