Synchronization and time transfer in wireless networks and method therefor
A method for synchronization and time transfer in a wireless system having a single timing source comprises: transmitting a timing message from a coordinator node, wherein the coordinator node is coupled to the single timing source of the wireless system; detecting the timing message by a wireless node; and synchronizing the wireless node to a time on the timing message.
1. A method for synchronization and time transfer in a wireless system having a single timing source comprising:
transmitting a timing message from a coordinator node, wherein the coordinator node is coupled to the single timing source of the wireless system;
detecting the timing message by a wireless node;
synchronizing the wireless node to a time on the timing message;
computing a delay time by the wireless node detecting the timing message, wherein the delay time is a time from when the wireless node detects the timing message to a next time slot;
determining a frame time by the wireless node, wherein the frame time is a time between when the timing message is sent and a next timing message is sent, the frame time comprising a plurality of time slots, each time slot being of a same duration; and
counting down to the next timing message by the wireless node once the frame time is determined to maintain a local system time and be synchronized with the coordinator node.
2. The method of claim 1 , comprising transmitting timing messages at a beginning of every frame time by the coordinator node.
3. The method of claim 1 , determining a transmit time between the coordinator node and the wireless node.
4. The method of claim 3 , wherein the transmit time is determined through Radio Frequency (RF) ranging.
5. The method of claim 3 , wherein determining the transmit time comprises:
sending a range request data package from the coordinator node at a time T 0 to the wireless node;
recording the time R 0 when the range request data package has been received by the wireless node;
sending a data package with the time R 0 by the wireless node to the coordinator node at a recorded time T 1 ;
recording a time R 1 when the data package with the time R 0 has been received by the coordinator node;
sending a data package with the time T 0 , R 0 , R 1 by the coordinator node to the wireless node at a time T 2 ;
recording a time R 2 when the data package with the data package of the times T 0 , R 0 , R 1 has been received by the wireless node;
sending a data package with the time T 0 , T 1 , R 0 , R 1 , R 2 by the wireless node to the coordinator node at a time T 3 ;
recording a time R 3 when the data package with the times T 0 , T 1 , R 0 , R 1 , R 2 has been received by the coordinator node;
computing the time delay by the coordinator node.
6. The method of claim 5 , comprising sending a data package with the transit time from the coordinator node to the wireless node.
7. The method of claim 5 , wherein the coordinator node computes the transit time using the formula:
Time
Delay
=
(
R
1
-
T
0
)
-
(
T
1
-
R
0
)
2
+
(
R
2
-
T
1
)
-
(
T
2
-
R
1
)
2
2
.
8. The method of claim 1 , comprising:
transmitting clock data from the single timing source to the coordinator node.
9. A method for synchronization and time transfer in a wireless system having a single timing source comprising:
transmitting timing messages at a predetermined time interval by a coordinator node, wherein a time between timing messages is defined as a frame time, the frame time comprising a plurality of time slots, each time slot being of a same duration, wherein the coordinator node is coupled to the single timing source;
detecting a first valid timing message sent by the coordinator node by a wireless node remote from the coordinator node;
synchronizing the wireless node to a time on the valid timing message;
computing a delay time by the wireless node detecting the timing message, wherein the delay time is a time from when the wireless node detects the timing message to a next time slot;
determining a frame time by the wireless node, wherein the frame time is a time between when the timing message is sent and a next timing message is sent, the frame time comprising a plurality of time slots, each time slot being of a same duration; and
counting down to the next timing message by the wireless node once the frame time is determined to maintain a local system time and be synchronized with the coordinator node.
10. The method of claim 9 , determining a transmit time between the coordinator node and the wireless node.
11. The method of claim 9 , wherein determining the transmit time comprises:
sending a range request data package from the coordinator node at a time T 0 to the wireless node;
recording the time R 0 when the range request data package has been received by the wireless node;
sending a data package with the time R 0 by the wireless node to the coordinator node at a recorded time T 1 ;
recording a time R 1 when the data package with the time R 0 has been received by the coordinator node;
sending a data package with the time T 0 , R 0 , R 1 by the coordinator node to the wireless node at a time T 2 ;
recording a time R 2 when the data package with the data package of the times T 0 , R 0 , R 1 has been received by the wireless node;
sending a data package with the time T 0 , T 1 , R 0 , R 1 , R 2 by the wireless node to the coordinator node at a time T 3 ;
recording a time R 3 when the data package with the times T 0 , T 1 , R 0 , R 1 , R 2 has been received by the coordinator node;
computing the time delay by the coordinator node.
12. The method of claim 10 , comprising sending a data package with the transit time from the coordinator node to the wireless node.
13. The method of claim 11 , wherein the coordinator node computes the transit time using the formula:
Time
Delay
=
(
R
1
-
T
0
)
-
(
T
1
-
R
0
)
2
+
(
R
2
-
T
1
)
-
(
T
2
-
R
1
)
2
2
.
14. The method of claim 9 , wherein the coordinator node and the wireless node operate in a 3 GHz to 6 GHz frequency range.
15. A wireless node system comprising:
a coordinator node coupled to a single timing source of the wireless node system, the coordinator node transmitting timing messages at a predetermined time interval, wherein a time between timing messages is defined as a frame time, the frame time comprising a plurality of time slots, each time slot being of a same duration, wherein the coordinator node is coupled to the single timing source; and
a plurality of wireless nodes in wireless communication with the coordinator node, wherein each of the plurality of wireless nodes detect a first valid timing message sent by the coordinator and synchronize to a time on the valid timing message;
wherein each of the wireless nodes computes a delay time, wherein the delay time is a time from when each of the wireless nodes detects the valid timing message to a next time slot;
wherein each of the wireless nodes determines a frame time, wherein the frame time is a time between when the timing message is sent and a next timing message is sent, the frame time comprising a plurality of time slots, each time slot being of a same duration; and
wherein each wireless node count down to the next timing message once the frame time is determined to maintain a local system time and be synchronized with the coordinator node.
16. The wireless node system of claim 15 , wherein the coordinator node calculates a transmit time between the coordinator node and each of the plurality of wireless nodes.
17. The wireless node system of claim 16 , wherein the coordinator node and each of the plurality of wireless nodes operate in a 3 GHz to 6 GHz frequency range.