Method and apparatus for tracking location of user equipment by using integrated GPS and TDOA scheme

• US 7,446,701 B2
• Filed: 11/10/2005
• Issued: 11/04/2008
• Est. Priority Date: 11/11/2004
• Status: Expired due to Fees

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Lim, Chang-Soo, Park, Byung-Jun
• Primary Examiner(s): Tarcza; Thomas H.
• Assistant Examiner(s): Nguyen; Nga X
• Application Number:
  US11/270,735
• Publication Number:
  US 20060232466A1
• Time in Patent Office: 1,090 Days
• Field of Search: 34235701-35717, 342/387
• US Class Current: 342/357.4
• CPC Class Codes: G01S 19/48 by combining or switching between position solutions derived from the satellite radio beacon positioning system and position solutions derived from a further system

Abstract

A method and an apparatus for tracking a location of a UE by using an integrated GPS and TDOA scheme in a mobile communication network are provided. A GPS position solution of the UE is obtained using GPS code information. TDOA position solutions are obtained using pilot signal transmission times of BSs and pilot signal reception times of the UE, and an average value of the TDOA position solutions is calculated. The GPS position solution is subtracted from the average to obtain a position error value, and an iterative method using a least square method is performed for the position error value to correct the position error. The corrected position error value is added to the average value of the TDOA position solutions to obtain a more precise position solution.

Claims

1. A method for tracking a location of a user equipment (UE) by using an integrated Global Positioning System (GPS) and Time Difference Of Arrival (TDOA) scheme in a mobile communication network, the method comprising the steps of:

obtaining a GPS position solution of the UE by using GPS code information, the GPS position solution being derived using a frequency corresponding to a clock period demultiplied by a chip rate of the mobile communication network;

obtaining TDOA position solutions by using transmission times of pilot signals transmitted from a plurality of base stations (BSs) and reception times of the pilot signals received at the UE, and calculating an average value of the TDOA position solutions;

obtaining a corrected position error value by subtracting the GPS position solution from the average of the TDOA position solutions to obtain a position error value, and performing an iterative method using the position error value; and

adding the corrected position error value to the average value of the TDOA position solutions.

2. The method as claimed in claim 1, wherein the iterative method is performed using a least square method.

3. The method as claimed in claim 1, wherein the reception time of the UE is obtained using a frequency corresponding to a GPS clock period demultiplied by a chip rate of the mobile communication network.

4. The method as claimed in claim 2, wherein the demultiplied frequency is 61.44 Mcps.

5. The method as claimed in claim 1, wherein the correction step comprises, for the calculated position solutions and the absolute position, performing a linearization through a Taylor series of an initial position of the UE, wherein

6. The method as claimed in claim 4, wherein calculation of h_i^T comprises using an equation

7. The method as claimed in claim 4, further comprising iteratively performing a calculation using equation,

δ

Û

=(A^TA)<sup>−

1</sup>A^Tδ

Z

where A denotes a state transition matrix,

8. The method as claimed in claim 5, wherein calculating a weighted least square adjustment solution for the equation and an estimated initial position covariance matrix comprises using

δ

Û

=(A^TQ_DTG<sup>−

1</sup>A)<sup>−

1</sup>A^TQ_DTG<sup>−

1</sup>δ

z

Σ

δ

Û

={circumflex over (σ

)}₀²(A^TQ_DTG<sup>−

1</sup>A)<sup>−

1</sup>.

9. The method as claimed in claim 7, wherein Q_DTG is a variable of w representing a difference covariance matrix of TDOA pseudo-ranges and GPS code pseudo-ranges the weighted least square filter, wherein,

Q_DTG=TG cov(TDOA)TG^T

where, cov(TDOA)=Ccov(R)C, C is a TDOA difference matrix, cov(R) is a covariance of noises measured between the BS and the UE, R is an error value of the position solution, and TG is a TDOA and GPS difference matrix.

10. The method as claimed in claim 8, wherein in the equation, using a remained value or a remainder after the least square method, a posterior variance estimation comprises using equation,

11. An apparatus for tracking a location of a user equipment (UE) by using an integrated Global Positioning System (GPS) and Time Difference Of Arrival (TDOA) scheme in a mobile communication network;

the apparatus comprising;

a GPS receiver unit for obtaining a GPS position solution of the UE by using GPS code information;

a TDOA calculation unit for obtaining TDOA position solutions by using transmission times of pilot signals transmitted from a plurality of base stations (BSs) and reception times of the pilot signals received at the UE, and calculating an average value of the TDOA position solutions;

a weighted least square filter for obtaining a corrected position error value by subtracting the GPS position solution from the average of the TDOA position solutions to obtain a position error value, and performing an iterative method using the position error value; and

an adder unit for adding the corrected position error value to the average value of the TDOA position solutions.

12. The apparatus as claimed in claim 11, wherein the iterative is performed using a least square method.

13. The apparatus as claimed in claim 11, wherein the reception time of the UE is obtained using a frequency corresponding to a GPS clock period demultiplied by a chip rate of the mobile communication network.

14. The apparatus as claimed in claim 11, wherein the demultiplied frequency is 61.44 Mcps.

15. The apparatus as claimed in claim 11, wherein for the calculated position solutions and the absolute position, the weighted least square filter performs linearization through a Taylor series of an initial position of the UE, and the linearization is using equation

16. The apparatus as claimed in claim 13, wherein calculation of h_i^T comprises using an equation

17. The apparatus as claimed in claim 13, wherein the weighted least square filter further performs an iterative calculation using an equation,

δ

Û

=(A^TA)<sup>−

1</sup>A^Tδ

z

where A denotes a state transition matrix,

18. The apparatus as claimed in claim 15, wherein calculating a least square adjustment solution for the equation and an estimated initial position covariance matrix comprises using

δ

Û

=(A^TQ_DTG<sup>−

1</sup>A)<sup>−

1</sup>A^TQ_DTG<sup>−

1</sup>δ

z

Σ

δ

Û

={circumflex over (σ

)}₀²(A^TQ_DTG<sup>−

1</sup>A)<sup>−

1</sup>.

19. The apparatus as claimed in claim 16, wherein “

Q_DTG”

is a variable of w representing a difference covariance matrix of TDOA pseudo-ranges and GPS code pseudo-ranges the weighted least square filter, wherein,

Q_DTG=TG cov(TDOA)TG_T

where cov(TDOA)=Ccov(R)C, C is a TDOA difference matrix, cov(R) is a covariance of noises measured between the BS and the UE, R is an error value of the position solution, and TG is a TDOA and GPS difference matrix.

20. The apparatus as claimed in claim 16, wherein in the equation, using a remained value or a remainder after the least square method, a posterior variance estimation comprises using equation,