SYSTEM AND METHOD FOR PASSIVELY DETERMINING OWN POSITION LISTENING TO WIRELESS TIME SYNCHRONIZATION COMMUNICATIONS

• US 20120252503A1
• Filed: 04/03/2012
• Published: 10/04/2012
• Est. Priority Date: 04/04/2011
• Status: Active Grant

• Current Assignee: Saab Inc (Saab AB)
• Original Assignee: Saab Sensis Corp. (Saab AB)
• Inventors: WU, Ryan Haoyun
• Granted Patent: US 9,060,342 B2
• Time in Patent Office: Days
• US Class Current: 455/456.6
• CPC Class Codes: G01S 5/10 Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements , e.g. omega or decca systemsG01S5/12 takes precedence ; beacons and receivers cooperating therewith G01S1/306, G01S1/308
• CPC Class Codes: H04W 56/0015 one node acting as a reference for the others
• CPC Class Codes: H04W 56/0055 determining timing error of reception due to propagation delay
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

The system and method of the present invention provides a mobile node (e.g., target), such as an aircraft, vehicle or mobile piece of equipment, the ability to determine its own position by passively listening to wireless time synchronization communications, such as IEEE 1588 Precision Time Protocol (PTP) messages, exchanged between nodes over a wireless network.

Claims

1. A method of enabling a receiver to passively determine its own position by receiving wireless messages within a wireless network, the method comprising:

transmitting and receiving a plurality of messages between at least two pairs of nodes of known position within the wireless network;

transmitting at least a transmit time of one of the messages and a receive time of another of the messages transmitted between the at least two nodes from one node of each pair of the at least two pairs of nodes;

passively receiving and decoding the plurality of messages transmitted between the at least two pairs of nodes at said receiver; and

determines own position for said receiver from (i) the known positions of the at least two pairs of nodes, (ii) reception time at said receiver of each of the plurality of messages transmitted between the at least two pairs of nodes, and (iii) the transmit time of one of the messages and the receive time of another of the messages transmitted by the one node of each pair of the at least two pairs of nodes.

2. The method of claim 1, further comprising periodically updating the locations of the each node of the at least two pairs of nodes via the wireless network.

3. A method for enabling a receiver to passively determine its own position by receiving wireless messages between transceivers, the method comprising:

transmitting a first message from a first transceiver of known position;

receiving the first message at a second transceiver of known position and transmitting a second message from the second transceiver;

receiving the second message at the first transceiver and transmitting a transmit time of the first message and a receive time of the second message from the first transceiver to the second transceiver;

transmitting a third message from a third transceiver of known position;

receiving the third message at a fourth transceiver of known position and transmitting a fourth message from the fourth transceiver;

receiving the fourth message at the third transceiver and transmitting a transmit time of the third message and a receive time of the fourth message from the third transceiver to the fourth transceiver;

passively receiving and decoding at said receiver (i) the first, second, third and fourth messages, (ii) the transmit time of the first message and the receive time of the second message transmitted to the second transceiver, and (iii) the transmit time of the third message and the receive time of the fourth message transmitted to the fourth transceiver; and

determining own position for said receiver from (i) the known positions of the first, second, third and fourth transceivers, (ii) reception times of the first, second, third and fourth messages at said receiver, (iii) the transmit time of the first message and the receive time of the second message transmitted to the second transceiver, and (iv) the transmit time of the third message and the receive time of the fourth message transmitted to the fourth transceiver.

4. The method of claim 3, further comprising periodically updating the locations of the first through fourth transceivers via the wireless network.

5. A system for enabling a receiver to passively determine its own position by receiving wireless messages within a wireless network, the system comprising:

at least two pairs of nodes of known position within the wireless network, each pair of nodes transmitting and receiving a plurality of messages between each other,

wherein one node of each pair of the at least two pairs of nodes transmits at least a transmit time of one of the messages and a receive time of another of the messages transmitted between the at least two nodes, and

wherein said receiver passively receives and decodes the plurality of messages transmitted between the at least two pairs of nodes and determines own position for said receiver from (i) the known positions of the at least two pairs of nodes, (ii) reception time at said receiver of each of the plurality of messages transmitted between the at least two pairs of nodes, and (iii) the transmit time of one of the messages and the receive time of another of the messages transmitted by the one node of each pair of the at least two pairs of nodes.

6. The system of claim 5, wherein the plurality of messages are IEEE 1588 wireless messages.

7. The system of claim 6, wherein the at least two pairs of nodes comprises at least one master node and at least two slave nodes and the locations of the at least one master node and the at least two slave nodes are periodically updated via the wireless network.

8. The system of claim 6, wherein said receiver

determines a TDOA between a first pair of nodes of the at least two pairs of nodes,

determines a TDOA between a second pair of nodes in which at least one of the nodes of the second pair of nodes is a different node than the first pair of nodes,

tracks TDOAs determined between the first pair of nodes and TDOAs determined between the second pair of nodes at said receiver, and

determines its own position by TDOA multilateration processing using at least the tracked TDOAs and known positions of the first pair and the second pair of nodes.

9. A system for enabling a receiver to passively determine its own position by receiving wireless messages between transceivers on a wireless network, the system comprising:

a first transceiver of known position transmitting a first message;

a second transceiver of known position receiving the first message and transmitting a second message;

a third transceiver of known position transmitting a third message; and

a fourth transceiver of known position receiving the third message and transmitting a fourth message,

wherein the first transceiver receives the second message and transmits a transmit time of the first message and a receive time of the second message to the second transceiver,

wherein the third transceiver receives the fourth message and transmits a transmit time of the third message and a receive time of the fourth message to the fourth transceiver,

wherein said receiver passively receives and decodes (i) the first, second, third and fourth messages, (ii) the transmit time of the first message and the receive time of the second message transmitted to the second transceiver, and (iii) the transmit time of the third message and the receive time of the fourth message transmitted to the fourth transceiver, and

wherein said receiver determines own position for said receiver from (i) the known positions of the first, second, third and fourth transceivers, (ii) reception times of the first, second, third and fourth messages at said receiver, (iii) the transmit time of the first message and the receive time of the second message transmitted to the second transceiver, and (iv) the transmit time of the third message and the receive time of the fourth message transmitted to the fourth transceiver.

10. The system of claim 9, wherein the plurality of messages are IEEE 1588 wireless messages.

11. The system of claim 10, wherein the first through fourth transceivers comprises at least one master node and at least two slave nodes and the locations of the at least one master node and the at least two slave nodes are periodically updated via the wireless network.

12. The system of claim 11, wherein at least one of said first through fourth transceivers is a boundary node.

13. The system of claim 11, wherein said receiver

determines a TDOA between the first and second transceivers,

determines a TDOA between the third and fourth transceivers,

tracks the TDOAs determined between the first and second transceivers and the TDOAs determined between the third and fourth transceivers at the receiver, and

determines its own position by TDOA multilateration processing using at least the tracked TDOAs and known positions of the first, second, third and fourth transceivers.

14. The system of claim 13, wherein Kalman filtering tracks the TDOAs and the determining of its own position by TDOA multilateration processing interpolates the Kalman filter tracked TDOAs to a predetermined point in time.

15. The system of claim 13, wherein the TDOA multilateration processing uses a Maximum Likelihood Estimation approach.

16. The system of claim 10, wherein said receiver determines TDOAs between the master node and each of the at least two slave nodes using the following equations:

17. The system of claim 10, wherein said receiver is a slave node on the wireless network including at least the first and second transceivers of said first through fourth transceivers, and synchronizes its clock with clocks of at least the first and second transceivers, wherein when a clock offset, b_e, for said receiver'"'"'s clock is known, said receiver determines its own position from (i) the known positions of at least the first and second transceivers of said first through fourth transceivers, (ii) reception times of at least the first and second messages of said first through fourth messages at said receiver, (iii) the transmit time of at least the first message, (iv) the receive time of at least the second message, and (v) the clock offset b_e.

18. The system of claim 17, wherein said receiver determines its own position by solving an intersection of at least one TDOA that is tracked to a predetermined point in time and at least one range that is tracked to the same predetermined point in time, wherein the at least one TDOA is calculated using (i) the known positions of at least the first and second transceivers of said first through fourth transceivers, (ii) reception times of at least the first and second messages of said first through fourth messages at said receiver, (iii) the transmit time of at least the first message, (iv) the receive time of at least the second message;

and

the at least one range is calculated using (i) the known positions of at least the first and second transceivers of said first through fourth transceivers, (ii) reception times of at least the first and second messages of said first through fourth messages at said receiver, (iii) the transmit time of at least the first message, (iv) the receive time of at least the second message, and (v) the clock offset b_e.

19. The system of claim 18, wherein Kalman filtering tracks the at least one TDOA and the at least one range and the at least one TDOA and the at least one range are interpolated to a predetermined point in time.

20. The system of claim 18, wherein the position determination using the at least one tracked TDOA and the at least one tracked range uses a Maximum Likelihood Estimation approach.

21. The system of claim 11, wherein at least one of said first through fourth transceivers is part of a unmanned aerial system (UAS).

22. The system of claim 11, wherein said receiver is part of a unmanned aerial system (UAS).