Subspace signature matching for location ambiguity resolution in wireless communication systems

• US 6,064,339 A
• Filed: 08/20/1998
• Issued: 05/16/2000
• Est. Priority Date: 01/08/1997
• Status: Expired due to Fees

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: US Wireless Corp. (Vontier Corp.)
• Inventors: Meng, Yan, Wax, Mati, Hilsenrath, Oliver
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): Phan, Dao L.
• Application Number:
  US09/137,640
• Time in Patent Office: 635 Days
• Field of Search: 342/417, 342/452, 342/450, 342/457, 455/422, 455/456, 455/457
• US Class Current: 342/417
• CPC Class Codes: G01C 21/26 specially adapted for navigation in a road network
• CPC Class Codes: G01S 1/022 Means for monitoring or calibrating
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/0218 Multipath in signal reception
• CPC Class Codes: G01S 5/0244 Accuracy or reliability of position solution or of measurements contributing thereto
• CPC Class Codes: G01S 5/02521 using a radio-map
• CPC Class Codes: H04L 67/04 specially adapted for terminals or networks with limited capabilities; specially adapted for terminal portability
• CPC Class Codes: H04L 67/51 Discovery or management thereof, e.g. service location protocol [SLP] or web services
• CPC Class Codes: H04L 67/52 specially adapted for the location of the user terminal
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

A method and apparatus reduces the ambiguities in the determination of cellular telephone locations in a location finding system based on the use of multipath signals. A location finding base station determines a signal signature from a subspace of an array covariance matrix. The signature is compared to a database of calibrated signal signatures and corresponding locations, and a set of likely locations whose calibrated signatures best match the measured signature is selected. A subset of most likely locations is selected from among the likely locations by comparing a function which represents how closely the measured signature matches the set of calibrated signatures with functions which represent how closely each likely signature matches the set of calibrated signatures. The locations corresponding to the best matching function are selected.

Claims

1. In a system for wireless transmitter location finding, a method for selecting from a set of calibrated transmitter locations a set of most likely locations, the method comprising:

measuring at a base station a transmitter signal signature R;

calculating a difference between a function L_R and each function L_R.sbsb.i in a set of functions L_R.sbsb.1, . . . , L_R.sbsb.M, where the function L_R represents how signature R compares to a set of calibrated signatures which corresponds to the set of calibrated locations, and where the functions L_R.sbsb.1, . . . , L_R.sbsb.M represent how each signature in a set of M calibrated signatures compares to the set of calibrated signatures;

selecting a set of most likely signatures, such that, for each most likely signature R_k, the calculated difference between the function L_R and L_R.sbsb.k is smaller than a predetermined threshold; and

identifying a subset of the set of calibrated transmitter locations, wherein each location in the subset corresponds to a signature in the selected subset of most likely signatures.

2. The method of claim 1 wherein the function L_R evaluated at a calibrated location i is a function of the cosines of the principle angles between a transmitter signature R and a calibrated signature U_i.

3. The method of claim 1 wherein the function L_R evaluated at a calibrated location i is a trace of a projection of R onto a subspace spanned by a calibrated signature U_i.

4. The method of claim 1 wherein the difference between the function L_R and each function L_R.sbsb.i is calculated by calculating a sum of squared distances between L_R and L_R.sbsb.i.

5. The method of claim 1 wherein the difference between the function L_R and each function L_R.sbsb.i is calculated by calculating the Kullback-Liebler distance between L_R and L_R.sbsb.i.

6. In a system for wireless transmitter location finding, a method for selecting from a set of calibrated transmitter locations a set of most likely locations, the method comprising:

measuring at a first base station a transmitter signal signature R;

measuring at a second base station a transmitter signal signature R'"'"';

calculating a difference between a function L_R and each function L_R.sbsb.i in a set of functions L_R.sbsb.1, . . . , L_R.sbsb.M, where the function L_R represents how signature R compares to a set of first base station calibrated signatures which corresponds to the set of calibrated locations, and where the functions L_R.sbsb.1, . . . , L_R.sbsb.M represent how each signature in a set of likely first calibrated signatures compares to the set of calibrated signatures;

calculating a difference between a function L_R'"'"' and each function L_R'"'"'.sbsb.i in a set of functions L_R'"'"'.sbsb.1, . . . , L_R'"'"'.sbsb.M, where the function L_R represents how signature R'"'"' compares to a set of second base station calibrated signatures which corresponds to the set of calibrated locations, and where the functions L_R'"'"'.sbsb.1, . . . , L_R'"'"'.sbsb.M represent how each signature in a set of likely second calibrated signatures compares to the set of second calibrated signatures;

selecting from the sets of first and second likely signatures a subset of most likely common signatures, such that, for each most likely signature R_k, and for each most likely signature R'"'"'_k, an arithmetic combination of the calculated difference between the functions L_R and L_R.sbsb.k, and the calculated difference between the function L_R and L_R.sbsb.k, is smaller than a predetermined threshold; and

identifying a subset of the set of calibrated transmitter locations, wherein each location in the subset corresponds to a signature in the selected subset of most likely signatures.

7. The method of claim 6 wherein the function L_R evaluated at a calibrated location i is a function of the cosines of the principle angles between the transmitter signature R and a calibrated signature U_i.

8. The method of claim 6 wherein the function L_R evaluated at a calibrated location i is a trace of a projection of R onto a subspace spanned by a calibrated signature U_i.

9. The method of claim 6 wherein the difference between the function L_R and each function L_R.sbsb.i is calculated by calculating a sum of squared distances between L_R and L_R.sbsb.i.

10. The method of claim 6 wherein the difference between the function L_R and each function L_R.sbsb.i is calculated by calculating the Kullback-Liebler distance between L_R and L_R.sbsb.i.