MITIGATING EFFECTS OF MULTIPATH DURING POSITION COMPUTATION

• US 20160109556A1
• Filed: 10/14/2015
• Published: 04/21/2016
• Est. Priority Date: 10/20/2014
• Status: Active Grant

• Current Assignee: NextNav, LLC
• Original Assignee: NextNav, LLC
• Inventors: Sendonaris, Andrew, Raghupathy, Arun
• Granted Patent: US 9,720,071 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01S 19/22 Multipath-related issues
• CPC Class Codes: G01S 19/428 using multipath or indirect path propagation signals in position determination
• CPC Class Codes: G01S 5/0218 Multipath in signal reception
• CPC Class Codes: G01S 5/0273 using multipath or indirect path propagation signals in position determination
• 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

Abstract

Estimating an unknown position of a receiver. In some embodiment, trilateration techniques that quantify uncertainty in the estimate of the unknown position are applied. One such technique for estimating a two-dimensional or three-dimensional position of a receiver uses an L-1 norm computation instead of an L-2 norm computation.

Claims

1. A method for estimating one or more positions of a receiver using signals received from a network of transmitters, the method comprising:

estimating a first latitude and a first longitude of first position of a receiver using a first objective function that calculates an L-1 norm of residuals.

2. The method of claim 1, wherein the method further comprises:

determining whether to estimate the first latitude and the first longitude using the first objective function or a second objective function that calculates an L-2 norm of residuals, wherein the determination is based on one or more of;

(1) data specifying a geographical region of the receiver, (2) data specifying whether the receiver is indoors or outdoors, or (3) data specifying a characteristic of a signal received by the receiver from a transmitter.

3. The method of claim 2, wherein the method further comprises:

determining whether to estimate the first latitude and the first longitude using the first objective function or the second objective function based on two or more data selected from the group of data consisting of;

(1) data specifying a geographical region of the receiver, (2) data specifying whether the receiver is indoors or outdoors, and (3) data specifying a characteristic of a signal received by the receiver from a transmitter.

4. The method of claim 2, wherein the method further comprises:

estimating the first latitude and the first longitude using the first objective function instead of the second objective function based on a cell ID, one or more satellite signals, or one or more local area network signals.

5. The method of claim 2, wherein the method further comprises:

estimating the first latitude and the first longitude using the first objective function instead of the second objective function when the data specifying the geographical region of the receiver indicates that the receiver is located in a first of at least two types of environments.

6. The method of claim 2, wherein the method further comprises:

estimating the first latitude and the first longitude using the first objective function instead of the second objective function when the data specifying the geographical region of the receiver indicates that the receiver is located in a first geographic region that includes more than a predefined number of buildings with heights that exceed a threshold height.

7. The method of claim 2, wherein the method further comprises:

estimating the first latitude and the first longitude using the first objective function instead of the second objective function when the data specifying whether the receiver is indoors or outdoors indicates that the receiver is indoors.

8. The method of claim 2, wherein the method further comprises:

estimating the first latitude and the first longitude using the first objective function instead of the second objective function when the data specifying the one or more characteristics indicates that each of the one or more signals meet a predefined multipath condition.

9. The method of claim 2, wherein the method further comprises:

estimating the first latitude and the first longitude using the first objective function instead of the second objective function when the data specifying the one or more characteristics indicates that one or more pseudorange measurements corresponding to the one or more signals each include a multipath error that exceeds a threshold amount of error.

10. The method of claim 1, wherein the method further comprises:

determining whether to estimate a second latitude and a second longitude of a second position of the receiver using the first objective function or a second objective function that calculates an L-2 norm of residuals, wherein the determination is based on data specifying a geographical region of the receiver; and

estimating the second latitude and the second longitude using the second objective function instead of the first objective function when the data specifying the geographical region of the receiver indicates that the receiver is not located in a first of at least two types of environments.

11. The method of claim 1, wherein the method further comprises:

determining whether to estimate a second latitude and a second longitude of a second position of the receiver using the first objective function or a second objective function that calculates an L-2 norm of residuals, wherein the determination is based on data specifying a geographical region of the receiver; and

estimating the second latitude and the second longitude using the second objective function instead of the first objective function when the data specifying a new geographical region of the receiver indicates that the receiver is located in a second geographic region that includes no more than a predefined number of buildings with heights that exceed a threshold height.

12. The method of claim 1, wherein the method further comprises:

determining whether to estimate a second latitude and a second longitude of a second position of the receiver using the first objective function or a second objective function that calculates an L-2 norm of residuals, wherein the determination is based on data specifying whether the receiver is indoors or outdoors; and

estimating the second latitude and the second longitude using the second objective function instead of the first objective function when data specifying whether the receiver is indoors or outdoors indicates that the receiver is outdoors.

13. The method of claim 1, wherein the method further comprises:

determining whether to estimate a second latitude and a second longitude of a second position of the receiver using the first objective function or a second objective function that calculates an L-2 norm of residuals, wherein the determination is based on data specifying a characteristic of a signal received by the receiver from a transmitter; and

estimating the second latitude and the second longitude using the second objective function instead of the first objective function when the data specifying the characteristic indicates that the signal does not meet a predefined multipath condition.

14. The method of claim 1, wherein the method further comprises:

determining whether to estimate a second latitude and a second longitude of a second position of the receiver using the first objective function or a second objective function that calculates an L-2 norm of residuals, wherein the determination is based on data specifying a characteristic of a signal received by the receiver from a transmitter; and

estimating the second latitude and the second longitude using the second objective function instead of the first objective function when the data specifying the one or more characteristics indicates that a pseudorange measurement corresponding to the signal does not include a multipath error that exceeds a threshold amount of error.

15. The method of claim 1, wherein the method further comprises:

estimating the first latitude and the first longitude using a second objective function that calculates an L-2 norm of residuals;

estimating movement of the receiver from an initial position to the first position using a sensor of the receiver;

selecting the estimates resulting from the first objective function or the estimates resulting from the second objective function based on the estimated movement; and

using the selected estimates to estimate the first position of the receiver.

16. The method of claim 1, wherein the method further comprises:

estimating the first latitude and the first longitude using a second objective function that calculates an L-2 norm of residuals;

estimating movement of the receiver from an initial position to the first position using a sensor of the receiver;

estimating the first latitude and the first longitude based on the estimated movement and initial latitude and initial longitude of the initial position; and

selecting between the estimates resulting from the first objective function and the estimates resulting from the second objective function based on a first comparison between the estimates resulting from the first objective function and the estimates based on the estimated movement of the receiver, and further based on a second comparison between the estimates resulting from the second objective function and the estimates based on the estimated movement of the receiver.

17. The method of claim 1, wherein the method further comprises:

determining an adjusted objective function that does not have a time bias parameter by inserting a time bias function into an objective function,

wherein the time bias function includes a weighted median when the adjusted objective function is the first objective function, and

wherein the time bias function includes a weighted mean when the adjusted objective function is a second objective function that calculates an L-2 norm of residuals.

18. The method of claim 1, wherein the method further comprises:

computing an estimate of a first altitude corresponding to the first position of the receiver using a pressure value measured by the receiver, wherein the first latitude and the first longitude are estimated by inputting the estimate of the first altitude into the first objective function.

19. The method of claim 1, wherein the method further comprises:

determining a global minimum from among two or more local minimums of the first objective function using a global optimization function that is based on a differential evolution approach for determining the global minimum.

20. The method of claim 1, wherein the method further comprises:

computing an estimate of a first altitude corresponding to the first position of the receiver using a pressure value measured by the receiver, wherein the first latitude and the first longitude are estimated by inputting the estimate of the first altitude into the first objective function; and

determining a global minimum from among two or more local minimums of the first objective function using a global optimization function that is based on a differential evolution approach for determining the global minimum.