Systems and methods for transparency mapping using multipath signals

• US 7,973,716 B2
• Filed: 09/17/2008
• Issued: 07/05/2011
• Est. Priority Date: 01/19/2005
• Status: Active Grant

• Current Assignee: Charles Stark Draper Laboratory Incorporated
• Original Assignee: Charles Stark Draper Laboratory Incorporated
• Inventors: Gustafson, Donald E., Elwell, John M. Jr.
• Primary Examiner(s): Issing; Gregory C
• Application Number:
  US12/212,475
• Publication Number:
  US 20090102707A1
• Time in Patent Office: 1,021 Days
• Field of Search: 342/453
• US Class Current: 342/453
• CPC Class Codes: G01C 21/206 specially adapted for indoor navigation
• 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 5/02521 using a radio-map
• CPC Class Codes: G01S 5/0273 using multipath or indirect path propagation signals in position determination

Abstract

Systems and methods for mapping a structure detect wireless signals, including at least one multipath signal that has experienced at least one reflection against a portion of the structure prior to the detection. The wireless signals are analyzed to estimate reflection points for the multipath signal(s), and a map of at least the portion of the structure is generated based on the estimated reflection points.

Claims

1. A method for mapping a structure, the method comprising:

detecting, at a receiver, a first wireless signal transmitted directly from a satellite;

deriving, from the first wireless signal, a location of the satellite;

detecting, at the receiver, a second wireless signal transmitted by the satellite, the second wireless signal having penetrated an exterior of a structure and having experienced a plurality of reflections inside the structure;

determining a time difference of arrival (TDOA) between the second wireless signal and the first wireless signal; and

developing a three-dimensional map of an interior of the structure based at least in part on the TDOA, a location of the receiver, and the location of the satellite.

2. The method of claim 1, wherein deriving the location of the satellite comprises deriving, from the first wireless signal, a code sequence and a data message.

3. The method according to claim 2, further comprising:

performing data wiping and coherent integration on the second wireless signal before determining the TDOA.

4. The method according to claim 2, further comprising:

detecting a signal having the first wireless signal and the second wireless signal mixed together;

synthesizing a replica of the detected signal by varying a first delay applied to the code sequence and mixing the resulting delayed code sequence with the code sequence until the resulting mixed code sequence matches the detected signal; and

correlating the replica with the detected signal by varying a second delay applied to the replica until a correlation peak occurs between the delayed replica and the detected signal.

5. The method according to claim 1, wherein a plurality of first wireless signals and a plurality of second wireless signals both originating from one or more satellites are detected, and the method further comprises:

isolating, from the pluralities of wireless signals, a subset of wireless signals that originate from a same satellite; and

identifying, from the subset of wireless signals, a direct path signal and at least one corresponding multipath signal that has experienced a plurality of reflections inside the structure.

6. The method according to claim 5, further comprising:

determining a delay between the at least one corresponding multipath signal and the direct path signal.

7. A system for mapping a structure, the system comprising:

a) a receiver at a known location; and

b) one or more signal processing elements operatively coupled to the receiver, the receiver and the signal processing elements being configured to;

i) detect a first wireless signal transmitted directly from a satellite,

ii) derive, from the first wireless signal, a location of the satellite,

iii) detect a second wireless signal transmitted by the satellite, and the second wireless signal having penetrated an exterior of a structure and having experienced a plurality of reflections inside the structure,

iv) determine a time difference of arrival (TDOA) between the second wireless signal and the first wireless signal, and

v) develop a three-dimensional map of an interior of the structure based at least in part on the TDOA, the location of the receiver, and the location of the satellite.

8. The system of claim 7, wherein the receiver and the signal processing elements are further configured to derive, from the first wireless signal, a code sequence and a data message.

9. The system according to claim 8, wherein the receiver and the signal processing elements are further configured to perform data wiping and coherent integration on the second wireless signal before determining the TDOA.

10. The system according to claim 8, wherein the receiver and the signal processing elements are further configured to:

i) detect a signal having the first wireless signal and the second wireless signal mixed together;

ii) synthesize a replica of the detected signal by varying a first delay applied to the code sequence and mixing the resulting delayed code sequence with the code sequence until the resulting mixed code sequence matches the detected signal; and

iii) correlate the replica with the detected signal by varying a second delay applied to the replica until a correlation peak occurs between the delayed replica and the detected signal.

11. The system according to claim 7, wherein a plurality of first wireless signals and a plurality of second wireless signals both originating from one or more satellites are detected, and wherein the receiver and the signal processing elements are further configured to:

i) isolate, from the pluralities of wireless signals, a subset of wireless signals that originate from a same satellite; and

ii) identify, from the subset of wireless signals, a direct path signal and at least one corresponding multipath signal that has experienced a plurality of reflections inside the structure.

12. The system according to claim 11, wherein the receiver and the signal processing elements are further configured to determine a delay between the at least one corresponding multipath signal and the direct path signal.