802.11mc Fine Timing Measurement (FTM), also known as Wi-Fi Round Trip Time (RTT), is a time-based measurement protocol that estimates the distance between FTM-capable Wi-Fi entities. In the context of this guide, the measured distance is between the FTM-capable AP and the FTM-capable Mobile Device, whereby the estimated distance is within one meter of precision. By calculating the distances between the device and multiple APs with known locations, the positions of the device can be determined.
A technique for calculating the round-trip time between an initiating and responding 802.11mc compliant unit is defined by the FTM protocol. A starting entity, such as the client (also known as STA), sends the FTM request frame to the corresponding entity, such as the AP. The responding entity, also referred to as the Responder, starts sending the FTM response frames requested by the client STA. To improve accuracy, the client STA must send FTM request frames to the collection of APs. The APs' responses are averaged across several frames to provide an accurate reading.
