Method and system for determining locations of mobile stations using directional corrections

• US 7,868,826 B1
• Filed: 07/31/2009
• Issued: 01/11/2011
• Est. Priority Date: 06/13/2006
• Status: Active Grant

• Current Assignee: Sprint Spectrum LP (Deutsche Telekom AG)
• Original Assignee: Sprint Spectrum LP (Deutsche Telekom AG)
• Inventors: Hou, Jiongkuan, Swift, James C.
• Primary Examiner(s): Tarcza; Thomas H
• Assistant Examiner(s): LIU, HARRY K
• Application Number:
  US12/533,471
• Time in Patent Office: 529 Days
• Field of Search: 342/357.2, 342/357.31, 342/451, 455/456.1
• US Class Current: 342/451
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location

Abstract

A base station almanac (BSA) stores directional forward link calibration (FLC) values that correct for differences between the listed locations of base station antennas and the actual locations of the antennas. Each directional FLC value is specific to wireless signals that are transmitted from a particular base station antenna and propagate toward a particular receiving area. A mobile station operating in a receiving area measures a wireless signal from a base station antenna located outside of the receiving area to obtain a signal measurement. The location of the mobile station is determined by applying a positioning algorithm that uses the signal measurement corrected by the directional FLC value for that particular combination of base station antenna and receiving area.

Claims

1. A method of correcting for a location difference between an actual location of a base station antenna and a listed location of said base station antenna, said method comprising:

(a) measuring a wireless signal transmitted from a base station antenna and received at a measurement point in a receiving area to obtain a signal measurement;

(b) obtaining a first location estimate of said measurement point by a first positioning method that uses said signal measurement and said listed location;

(c) obtaining a second location estimation of said measurement point by a second positioning method, wherein said second location estimate is more accurate than said first location estimate;

(d) calculating a correction value based, at least in part, on said first and second location estimates such that said correction value corrects for said location difference;

performing steps (a) through (d) for a plurality of different measurement points in said receiving area to obtain a plurality of correction values; and

averaging said plurality of correction values to obtain a directional forward link calibration (FLC) value that is specific for wireless signals that propagate from said base station antenna toward said receiving area.

2. The method of claim 1, wherein said signal measurement is a phase of a pilot signal transmitted from said base station antenna.

3. The method of claim 2, wherein said first positioning method is an advanced forward link trilateration (AFLT) positioning method or a hybrid positioning method.

4. The method of claim 3, wherein said second positioning method is a Global Positioning System (GPS)-based positioning method.

5. The method of claim 1, further comprising:

storing said directional FLC value in a base station almanac (BSA).

6. The method of claim 5, further comprising:

using said directional FLC value stored in said BSA to correct a subsequent measurement of a wireless signal transmitted from said base station antenna and received in said receiving area.