Integrity monitoring for geo-location systems

• US 20030054759A1
• Filed: 08/30/2001
• Published: 03/20/2003
• Est. Priority Date: 08/30/2001
• Status: Active Grant

• Current Assignee: Nokia of America Corporation (Nokia Corporation)
• Original Assignee: Alcatel-Lucent USA, Inc. (Nokia Corporation)
• Inventors: Da, Ren, Richton, Robert Ellis
• Granted Patent: US 7,499,710 B2
• Time in Patent Office: Days
• US Class Current: 455/7
• CPC Class Codes: G01S 19/20 Integrity monitoring, fault detection or fault isolation of space segment
• CPC Class Codes: G01S 19/42 Determining position
• CPC Class Codes: G01S 19/46 the supplementary measurement being of a radio-wave signal type

Abstract

Weighted ridge regression (WRR) processing is applied to three or more distance measurements to determine the location of a terminal. For example, in an integrated satellite-based navigation system/wireless network, the location of a mobile unit can be determined by applying WRR processing to at least three distance measurements, where one or more of the distance measurements are satellite-based distance measurements (e.g., GPS pseudorange measurements) and one or more are wireless network-based distance measurements (e.g., round-trip delay or pilot phase offset measurements). WRR processing provides improved accuracy in the determination of mobile unit position over conventional least mean square techniques.

Claims

1. A method for determining location of a terminal, comprising the steps of:

(a) assigning a weight value to at least one of a set of three or more distance measurements corresponding to three or more different sources relative to the terminal to generate a weighted set of distance measurements;

(b) assigning a value for an insertion parameter; and

(c) performing weighted ridge regression (WRR) processing based on the weighted set of distance measurements and the insertion parameter to determine a WRR estimate representing the location of the terminal.

2. The invention of claim 1, wherein:

the terminal is a mobile unit in a wireless network; and

at least one of the distance measurements is a wireless network-based distance measurement.

3. The invention of claim 2, wherein at least one of the distance measurements is a satellite-based distance measurement.

4. The invention of claim 2, wherein all of the distance measurements are wireless network-based distance measurements.

5. The invention of claim 2, wherein the at least one wireless network-based distance measurement is a round-trip delay (RTD) distance measurement.

6. The invention of claim 2, wherein the at least one wireless network-based distance measurement is a pilot phase offset (PPO) distance measurement.

7. The invention of claim 1, wherein at least one of the distance measurements is a satellite-based distance measurement.

8. The invention of claim 7, wherein all of the distance measurements are satellite-based distance measurements.

9. The invention of claim 7, wherein the at least one satellite-based distance measurement is a GPS pseudorange measurement.

10. The invention of claim 1, wherein step (c) comprises the step of evaluating the following equation:

11. The invention of claim 1, wherein step (b) comprises the steps of:

(1) computing a geometric dilution of precision (GDOP) value based on locations of the sources of the distance measurements; and

(2) setting the value for the insertion parameter based the GDOP value.

12. The invention of claim 11, wherein the GDOP value is calculated using the following equation:

13. The invention of claim 11, wherein step (c) comprises the steps of

(a) performing a least mean square algorithm to calculate the location of the terminal, if the GDOP value is less than a specified threshold;

and

(b) performing the WRR processing, if the GDOP value is not less than the specified threshold.

14. The invention of claim 1, wherein a weight value is assigned to each distance measurement, wherein at least two of the distance measurements are assigned different weight values.

15. The invention of claim 1, wherein:

the terminal is a mobile unit in a wireless network;

at least one of the distance measurements is a wireless network-based distance measurement;

at least one of the distance measurements is a satellite-based distance measurement;

a weight value is assigned to each distance measurement, wherein at least two of the distance measurements are assigned different weight values;

step (b) comprises the steps of;

(1) computing a geometric dilution of precision (GDOP) value based on locations of the sources of the distance measurements using the following equation;

$\mathrm{GDOP}=\sqrt{{\mathrm{Tr}<br><br>\left[H^T<br><br>H\right]}^{-1}}$

 

wherein;

Tr is a trace operator;

H is a predictor matrix based on the locations of the sources of the distance measurements; and

H¹ is a transpose of the predictor matrix H; and

(2) setting the value for the insertion parameter based the GDOP value; and

step (c) comprises the step of evaluating the following equation;

${\hat{x}}_{\mathrm{WRR}}={\left(H^T<br><br>\mathrm{WH}+\mathrm{kI}\right)}^{-1}<br><br>H^T<br><br>\mathrm{Wy}$

 

wherein;

{circumflex over (x)}_WRR is the WRR estimate;

W is a weighting matrix based on the one or more assigned weights;

k is the insertion parameter;

I is an identity matrix; and

y is a measurement vector based on the distance measurements.

16. The invention of claim 15, wherein step (c) comprises the steps of

(a) performing a least mean square algorithm to calculate the location of the terminal, if the GDOP value is less than a specified threshold;

and

(b) performing the WRR processing, if the GDOP value is not less than the specified threshold.

17. A machine-readable medium, having encoded thereon program code, wherein, when the program code is executed by a machine, the machine implements a method for determining location of a terminal, comprising the steps of:

(a) assigning a weight to at least one of a set of three or more distance measurements corresponding to three or more different sources relative to the terminal to generate a weighted set of distance measurements;

(b) assigning a value for an insertion parameter; and

(c) performing weighted ridge regression (WRR) processing based on the weighted set of distance measurements and the insertion parameter to determine a WRR estimate representing the location of the terminal.