US 12,411,202 B2
Estimating position from reference signals received by coordinating access points
Domenico Ficara, Essertines-sur-Yverdon (CH); Pascal Thubert, Roquefort les Pins (FR); Jerome Henry, Pittsboro, NC (US); Amine Choukir, Lausanne (CH); and Brian Hart, Sunnyvale, CA (US)
Assigned to Cisco Technology, Inc., San Jose, CA (US)
Filed by Cisco Technology, Inc., San Jose, CA (US)
Filed on Dec. 14, 2022, as Appl. No. 18/065,871.
Prior Publication US 2024/0201306 A1, Jun. 20, 2024
Int. Cl. G01S 5/00 (2006.01); G01S 5/02 (2010.01); H04J 3/06 (2006.01)
CPC G01S 5/0036 (2013.01) [G01S 5/02216 (2020.05); H04J 3/0661 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A method of a first access point (AP) for identifying a location of a wireless device, comprising:
transmitting a first reference signal to a second AP and a third AP to measure a round trip time and compute a distance;
receiving a first acknowledgment message from each of the second AP and the third AP including at least time information from the respective AP;
after a period of time subsequent to receiving the first acknowledgement message, transmitting a second reference signal to the second AP and the third AP;
receiving a second acknowledgment message from each of the second AP and the third AP;
for each the second AP and the third AP, calculating a clock drift using the first acknowledgment message and the second acknowledgment message, respectively;
transmitting a request message to the wireless device for identifying a position of the wireless device;
receiving a response message from the wireless device;
determining first time information based on a time of flight (ToF) of the request message and the response message, wherein the ToF corresponds to a distance of the wireless device from the AP;
receiving a second message from the second AP that includes second time information associated with the request message and the response message;
receiving a third message from the third AP that includes third time information associated with the request message and the response message; and
estimating a location of the wireless device based at least on the second time information, the third time information and adjusting the second and third timing information using the clock drift associated with the second AP and the third AP.