Systems and methods for space-time determinations with reduced network traffic

• US 8,717,919 B2
• Filed: 07/15/2011
• Issued: 05/06/2014
• Est. Priority Date: 02/12/2009
• Status: Expired due to Fees

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Rhoads, Geoffrey, Freer, Harrison, Brunk, Hugh L.
• Primary Examiner(s): PHUNKULH, BOB A
• Application Number:
  US13/184,308
• Publication Number:
  US 20110274004A1
• Time in Patent Office: 1,026 Days
• Field of Search: 370/241, 370/252, 342104-146, 342350-465, 709 1-302
• US Class Current: 370/252
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/0289 of multiple transceivers, e.g. in ad hoc networks
• CPC Class Codes: H04J 3/0664 unidirectional timestamps
• CPC Class Codes: H04J 3/0676 Mutual

Abstract

Space-time solutions are determined by exchanging pings among nodes in a network. Each ping includes a current space-time state of the transmitting node, which includes the transmitting node'"'"'s currently estimated location and corrected time (as a count stamp). A particular node in the network receives pings from the other nodes in the network and uses the data in the received pings to estimate its own current position and to correct its own free-running clock relative to a common system time. As a service to the network, the particular node then transmits its corrected time (as a count stamp) and estimated position to the other nodes. In some embodiments, the space-time solutions discussed herein are used as backup to other navigation systems, such as the Automatic Dependent Surveillance-Broadcast (ADS-B) system.

Claims

1. A method of determining location and timing information of a local node in a network, the method comprising:

receiving pings from a plurality of nodes in the network, the pings comprising a local clock solution of a transmitting node and a location of the transmitting node corresponding to when the local clock solution is transmitted, the local clock solution based on an independent local clock of the transmitting node as correlated with a network time by one or more clock solutions;

for each ping received within a predetermined time interval, associating a receive count stamp with the received ping, the receive count stamp corresponding to a local time when the ping is received, the local time based on an independent local clock of a receiving node;

and

processing the local clock solution of the transmitting node, the location of the transmitting node and the receive count stamps corresponding to the pings received within the predetermined time interval to determine one or more clock solutions for correlating the independent local clock of the receiving node with the network time, and to determine one or more location solutions for estimating a local location of the receiving node.

2. The method of claim 1, further comprising:

processing the one or more clock solutions and the one or more location solutions to determine a local space-time state comprising;

a local count stamp corresponding to a local time when the local space-time state is transmitted, the local time based on the independent local clock as correlated with the network time by the one or more clock solutions; and

a local location corresponding to when local space-time state is transmitted, the transmitted local location estimated using the one or more location solutions and the local count stamp.

3. The method of claim 2, further comprising:

transmitting the local space-time state to the plurality of nodes in the network.

4. The method of claim 1, further comprising:

providing an initial local space-time state based on data received from a timing and/or location system.

5. The method of claim 4, further comprising:

transmitting the initial local space-time state to the plurality of nodes in the network.

6. The method of claim 4, further comprising:

determining the receive count stamps associated with each ping received during an initial solution period based on the initial local space-time state.

7. The method of claim 4, further comprising:

determining the local location associated with each ping received during an initial solution period based on the initial local space-time state.

8. The method of claim 4, further comprising:

determining an initial direction vector between a remote node and a local node based on the data received from the timing and/or location system.

9. The method of claim 4, wherein the timing and/or location system comprises a satellite based global positioning system (GPS).

10. The method of claim 4, wherein the timing and/or location system comprises an Automatic Dependent Surveillance-Broadcast (ADS-B) system, and wherein at least one of the plurality of nodes is located within an aircraft, the method further comprising:

determining that satellite based navigation used by the ADS-B system is unavailable; and

in response to the unavailability of the satellite based navigation, determining the one or more clock solutions and the one or more location solutions.

11. A system for determining location and timing information, the system comprising:

a plurality of nodes in communication with one another, each node comprising;

an independent clock for generating count stamps;

a communication device for receiving remote pings from the other nodes, the remote pings comprising a local clock solution of a transmitting node and a location of the transmitting node corresponding to when the local clock solution is transmitted, the local clock solution based on an independent local clock of the transmitting node as correlated with a network time by one or more clock solutions; and

a processor for;

associating each remote ping with a receive count stamp based on the independent clock;

associating each remote ping with a local location; and

processing the local clock solution, the location of the transmitting node and, the receive count stamps to determine one or more clock solutions for correlating the independent clock with the network time, and to determine one or more location solutions for estimating a local location.

12. The system of claim 11, wherein the processor of each node is further configured to process the one or more clock solutions and the one or more location solutions to determine a local space-time state, and wherein the communication device of each node is further configured to transmit its local space-time state to the other nodes in the network.

13. The system of claim 11, wherein the communication device of each node is further configured to receive an initial local space-time state based on data received from a timing and/or location system and to transmit the initial local space-time state to the other nodes, and wherein the processor of each node is further configured to determine the receive count stamps and the local locations associated with each received remote ping based on the initial local space-time state.

14. The system of claim 13, wherein the timing and/or location system comprises a satellite based global positioning system (GPS).

15. The system of claim 13, wherein the timing and/or location system comprises an Automatic Dependent Surveillance-Broadcast (ADS-B) system, wherein at least one of the plurality of nodes is located within an aircraft, and wherein the processor of each node is further configured to:

determine that satellite based navigation used by the ADS-B system is unavailable; and

in response to the unavailability of the satellite based navigation, determine the one or more clock solutions and the one or more location solutions.