US 7,577,169 B1
Time stamping
Son Dinh, San Diego, Calif. (US); Keith Church, San Diego, Calif. (US); and Ilya Stevens, San Diego, Calif. (US)
Assigned to The United States of America as represented by the Secretary of the Navy, Washington, D.C. (US)
Filed on Nov. 30, 2005, as Appl. No. 11/290,254.
Int. Cl. H04J 3/06 (2006.01)
U.S. Cl. 370—509  [370/350; 370/516] 18 Claims
OG exemplary drawing
 
1. A method of time stamping, the method comprising the steps of:
a. initiating a time stamp request message at a lower data link layer of a requester wherein said data link layer is comprised of hardware which includes embedded processors to enable said data link layer of said requestor to perform Vernier interpolation;
b. time stamping a transmit time of said time stamp request message at said lower data link level of said requester;
c. recording an arrival time of said time stamp request message at a said lower data link level of a responder, wherein said data link layer is comprised of hardware which includes embedded processors to enable said data link layer of said requestor to perform Vernier interpolation;
d. receiving said time stamp request message at said lower data link level of said responder;
e. initiating a time stamp response message at said lower data link level of said responder;
f. time stamping a transmit time of said time stamp response message at said lower data link level of said responder;
g. recording an arrival time of said time stamp response message at said lower data link level of said requestor;
h. receiving said time stamp response message at said lower data link level of said requestor; and
i. adjusting a requester clock using a clock offset and path delay determined by equations utilizing the synchronization parameters Time 1 (T1), Time 2 (T2), Time 3 (T3) and Time 4 (T4) which have been calculated selectively using Vernier interpolation as follows:
path delay=[(T2−T1)−(T3−T4)]/2
clock offset=[(T2−T1)+(T3−T4)]/2
where
T1 represents transmit time of said time stamp request message
T2 represents arrival time of said time stamp request message
T3 represents transmit time of said time stamp response message
T4 represents arrival time of said time stamp response message.