Everyone thanks for coming back to Wi Fi fundamentals with location and analytics. This course will help you to muster the air. Up until now we've used one access point and one station to determine distance, edit more access points and you will be able to catch precise location up to one meter. Let's recap. We have an initiator and the responder. This station asks our access point an FTM request, the access point acknowledge and then it sends an FTM departure frame.
This station receives the frame, timestamp it and sends an acknowledgement the access points gets the frame and times template. It then sends the station another message with the two timestamps T one and T four. To gain precise location, several things must happen timestamps must be accurate tree access point must be installed in order to get to D position. Wider channels are preferred for best accuracy. The wider the channel the higher resolution it is, and it is preferred to have a line of sight. Most of the time this is not the case.
So the closest path to a line of sight is measured. And another thing placement. The access point height above floor plan is important for precise location. As part of the FPM session, access point actually share an internal location information that is part of the frame. It is called in LCI a location configuration information. And that actually includes the latitude, the longitude, and the altitude the height of the access point.
And FDM session can be requested pre or post Association. So station can actually ask the access point for its location, even if it is not connected to it. Another field in the FTM frame is civic address. As the name implies, civic address includes the street name, number, and even the name of the building the access point resides in LCI and civic address are not configured manually. They are obtained via new DHCP options for MCI and civic information. into the location information as LCI and specific address can also be shared by access point using neighbor report.
Neighbor report is used for quite some time by 802 11 k protocol to share information as neighboring access point and channels to help roaming be faster. Wi Fi RTT extended it for its own purposes. LCI information exchange can be used by devices and stations to realize where am I all by access points. To realize where are you asking the station. Location algorithm can be done using different techniques, one of which we have already learned of is trilateration