US 11,902,016 B2
Ranging between unsynchronized communication terminals
P. Stephan Bedrosian, McLean, VA (US)
Assigned to MITRE Corporation, McLean, VA (US)
Filed by MITRE Corporation, McLean, VA (US)
Filed on Nov. 30, 2021, as Appl. No. 17/538,146.
Prior Publication US 2023/0171013 A1, Jun. 1, 2023
Int. Cl. H04W 56/00 (2009.01); H04J 3/06 (2006.01); H04L 43/0864 (2022.01)
CPC H04J 3/0661 (2013.01) [H04L 43/0864 (2013.01); H04W 56/0065 (2013.01)] 18 Claims
OG exemplary drawing
 
1. A method for determining a range between two unsynchronized communications terminals comprising:
transmitting, by a first terminal, a range request to a second terminal over a line of sight channel, wherein the first and second terminals are independently in motion with respect to each other and have unsynchronized timing domains, wherein the terminals are satellites;
storing, by the first terminal, a first timestamp in memory corresponding to a time at which the range request message was transmitted;
receiving, by the first terminal from the second terminal, a range response to the range request, the range response including a residence time that characterizes an amount of time the second terminal required to send the range response after receiving the range request;
storing, by the first terminal, a second timestamp in memory corresponding to a time at which the range response was received;
calculating a roundtrip time for the range request and range response based on the second timestamp minus the first timestamp and the residence time;
calculating a distance between the first terminal and the second terminal based on the roundtrip time;
repeatedly measuring a doppler effect through a periodic sequence of range measurements; and
using the doppler effect measurements to compute a corrected range.