Global positioning method, terminal, and system

• US 6,437,736 B2
• Filed: 05/09/2001
• Issued: 08/20/2002
• Est. Priority Date: 12/28/1998
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Hirata, Seiichiro, Ueda, Fumio
• Primary Examiner(s): PHAN, DAO LINDA
• Application Number:
  US09/851,097
• Publication Number:
  US 20010028322A1
• Time in Patent Office: 468 Days
• Field of Search: 342/357.01, 342/357.05, 342/357.06, 342/357.12, 701/213, 701/215, 455/12.1
• US Class Current: 342/357.62
• CPC Class Codes: G01S 19/05 providing aiding data
• CPC Class Codes: G01S 19/243 Demodulation of navigation message
• CPC Class Codes: G01S 19/246 involving long acquisition integration times, extended snapshots of signals or methods specifically directed towards weak signal acquisition
• CPC Class Codes: G01S 19/254 relating to Doppler shift of satellite signals
• CPC Class Codes: G01S 19/256 relating to timing, e.g. time of week, code phase, timing offset
• CPC Class Codes: G01S 19/258 relating to the satellite constellation, e.g. almanac, ephemeris data, lists of satellites in view
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence
• CPC Class Codes: G01S 19/30 code related G01S19/246 takes precedence

Abstract

A Global Positioning System forms a C/A code sequence by summing up, beginning from a polarity inversion boundary determined by a correlation peak position detector, chips at corresponding positions in PN frames constituting each bit of navigation data; calculates pseudo ranges by computing correlation between the C/A code sequence and a reference C/A code sequence generated by a GPS terminal; and determines the position of the GPS terminal using the pseudo ranges and navigation data. The navigation data detected inside the GPS terminal is used when a received electric field detected by a received electric field intensity detector is greater than a predetermined level, and the navigation data received from an external system is used when the received electric field is below the predetermined level. This makes it possible to solve following problems of a conventional system: the number of PN frames to be integrated is limited because the conventional system does not detect the polarity inversion boundaries of the navigation data, and hence the sensitivity (S/N ratio) is insufficient; and the communication between a terminal and a base station is required for determining the position because the GPS terminal always obtains the Doppler information from the base station, increasing the communication cost.

Claims

1. A global positioning system (GPS) positioning method comprising:

obtaining data having a polarity from a GPS signal,

changing the polarity based on navigation data and cumulatively summing the data at corresponding same bit positions per portion corresponding to a clear and acquisition (C/A) code length to produce a sum,

computing correlation between the sum and a C/A code,

detecting a correlation peak position based on a correlation peak value obtained from computing the correlation, and

detecting a pseudo range between a GPS terminal and a satellite corresponding to the C/A code, based on the correlation peak position.

2. The GPS positioning method of claim 1 further comprising shifting the navigation data, and changing the polarity based on the navigation data shifted if a correlation peak value is not obtained.

3. The GPS positioning method of in claim 2 wherein the shifting of navigation data is toward maximizing the correlation peak value.

4. The GPS positioning method of claim 2 including shifting the navigation data by a fixed value.

5. The GPS positioning method of claim 2 including shifting the navigation data by a variable value.

6. The GPS positioning method of claim 1 including making a first Doppler correction for the GPS signal using Doppler information obtained from the GPS signal.

7. The GPS positioning method of claim 6 including making a second Doppler correction for the data having polarity using Doppler information obtained from the GPS signal, after the first Doppler correction.

8. The GPS positioning method of claim 1 including, upon receipt of the GPS signal, detecting electric field intensity of the GPS signal, and changing length of the data according to the electric field strength of the GPS signal.

9. A global positioning system (GPS) GPS positioning method comprising:

receiving a GPS signal and detecting electric field intensity of the GPS signal,

selecting navigation data obtained by a GPS terminal based on the GPS signal if the electric field strength exceeds a threshold and selecting the navigation data obtained by an external system based on the GPS signal if the electric field strength does not exceed the threshold, and

detecting position of said GPS terminal based on the navigation data selected.

10. A global positioning system (GPS) terminal comprising

a data obtaining section for obtaining data having a polarity from a GPS signal,

a data processing section for changing the polarity based on the navigation data obtained from the GPS signal and cumulatively summing the data at corresponding same bit positions per portion corresponding to a clear and acquisition (C/A) code length,

a correlation calculating section for computing correlation between the cumulative summary and a C/A code, and

a pseudo range calculating section for calculating a pseudo range between the GPS terminal and a satellite corresponding to the C/A code, based on a correlation peak produced by said correlation calculating section.

11. A global positioning system (GPS) terminal comprising:

a received electric field detector for receiving a GPS signal and detecting received electric field strength of the GPS signal,

a selecting section for selecting the navigation data obtained by a GPS terminal based on the GPS signal if the received electric field strength exceeds a threshold and for selecting navigation data obtained by an external system, based on the GPS signal if the received electric field strength does not exceed the threshold, and a position calculating section for detecting position of the GPS terminal based on the navigation data selected.

12. A global positioning system (GPS) positioning system comprising an external system for obtaining navigation data from a GPS signal and a GPS terminal for conducting calculation using the navigation data from said external system, wherein said GPS terminal comprises:

a data obtaining section for obtaining data having a polarity from a GPS signal,

a data processing section for changing the polarity based on the navigation data obtained from the GPS signal and cumulatively summing the data at corresponding same bit positions per portion corresponding to a clear and acquisition (C/A) code length,

a correlation calculating section for computing correlation between the cumulative summary and a C/A code, and

a pseudo range calculating section for calculating a pseudo range between the GPS terminal and a satellite corresponding to the C/A code, based on a correlation peak produced by said correlation calculating section.

13. The GPS positioning system described in claim 12, wherein said data processing section shifts the navigation data if a correlation peak obtained by said correlation calculating section does not reach a correlation peak value, and changes the polarity based on the navigation data shifted.

14. A global positioning system (GPS) positioning system comprising an external system for obtaining navigation data from a GPS signal and a GPS terminal for receiving the navigation data from said external system, wherein said GPS terminal comprises:

a received electric field detector for receiving a GPS signal and detecting received electric field strength of the GPS signal,

a selecting section for selecting the navigation data obtained by a GPS terminal based on the GPS signal if the received electric field strength exceeds a threshold and for selecting navigation data obtained by an external system, based on the GPS signal if the received electric field strength does not exceed the threshold, and a position calculating section for detecting position of the GPS terminal based on the navigation data selected.

15. The GPS positioning system described in claim 14, wherein said GPS terminal comprises

a data obtaining section for obtaining data having a polarity from a GPS signal,

a data processing section for changing the polarity based on one of the navigation data obtained from the GPS signal and the navigation data obtained from said external system based on the GPS signal, and cumulatively summing the data at corresponding same bit positions per portion corresponding to a clear and acquisition (C/A) code length,

a correlation calculating section for computing correlation between the cumulative summary and a C/A code, and

a pseudo range calculating section for calculating a pseudo range between the GPS terminal and a satellite corresponding to the C/A code, based on a correlation peak produced by said correlation calculating section.