Method and apparatus for decoding satellite navigation data from a satellite positioning system

• US 20060126762A1
• Filed: 12/10/2004
• Published: 06/15/2006
• Est. Priority Date: 02/06/2004
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Global Locate Incorporated (Broadcom, Inc.)
• Inventors: Abraham, Charles, Tapucu, Emre, Diggelen, Frank Van
• Granted Patent: US 7,924,947 B2
• Time in Patent Office: Days
• US Class Current: 375/340
• CPC Class Codes: G01S 19/243 Demodulation of navigation message

Abstract

Method and apparatus for decoding a bitstream of navigation data broadcast by a satellite positioning system satellite is described. In one example, a portion of a subframe in the navigation data for each of a plurality of occurrences of the subframe in the bitstream is obtained at a satellite signal receiver to produce a respective plurality of subframe portions. The subframe portions are then combined to recover the subframe. The subframe portions may be processed to maintain a constant polarity by comparing a common sequence of data bits among at least two of the subframe portions to identify a mismatch in polarity.

Claims

1. A method of decoding a bitstream of navigation data broadcast by a satellite positioning system satellite, comprising:

obtaining, at a satellite signal receiver, a portion of a subframe in said navigation data for each of a plurality of occurrences of said subframe in said bitstream to produce a respective plurality of subframe portions; and

combining said plurality of subframe portions to recover said subframe.

2. The method of claim 1, further comprising:

processing said plurality of subframe portions to maintain a constant polarity.

3. The method of claim 2, wherein said step of processing comprises:

comparing a common sequence of data bits among at least two of said plurality of subframe portions to identify a mismatch in polarity.

4. The method of claim 1, further comprising:

repeating said steps of obtaining and combining with respect to at least one additional subframe in said navigation data.

5. The method of claim 1, wherein said step of obtaining comprises, for each of said plurality of occurrences of said subframe in said bitstream:

decoding at least one word from said bitstream;

checking parity for each said at least one word; and

retaining each said at least one word that passes parity in a buffer.

6. The method of claim 1, further comprising:

decoding a first data set identifier from said bitstream during a first occurrence of said plurality of occurrences of said subframe;

decoding a second data set identifier from said bitstream during a second occurrence of said plurality of occurrences of said subframe; and

comparing said first data set identifier and said second data set identifier to validate said recovered subframe.

7. The method of claim 6, wherein said satellite positioning system satellite comprises a Global Positioning System (GPS) satellite, said navigation data comprises GPS navigation data, and each of said first data set identifier and said second data set identifier comprises an IODE parameter.

8. The method of claim 1, further comprising:

analyzing polarity verification markers in said recovered subframe; and

inverting said recovered subframe in response to said polarity verification markers being inverted.

9. A method of decoding a bitstream of navigation data broadcast by a satellite positioning system satellite, comprising:

(a) decoding a word of a subframe in said navigation data from said bitstream;

(b) checking parity for said word;

(c) if said word passes parity, retaining said word in a buffer;

(d) repeating said steps (a) through (c) a plurality of times to produce a portion of said subframe;

(e) repeating said steps (a) through (d) for a plurality of occurrences of said subframe in said bitstream to produce a respective plurality of subframe portions; and

(f) combining said plurality of subframe portions to recover said subframe.

10. The method of claim 9, further comprising:

(g) repeating said steps (a) through (f) with respect to at least one additional subframe in said navigation data.

11. The method of claim 9, wherein said step (c) comprises:

(c1) analyzing common bits between said word and at least one neighboring word stored in said buffer to detect inverted bits; and

(c2) responsive to said inverted bits, performing at least one of;

inverting said word; and

inverting at least one other word stored in said buffer.

12. The method of claim 9, further comprising:

(g) decoding a first data set identifier from a first word stored in said buffer during a first occurrence in said plurality of occurrences of said subframe;

(h) decoding a second data set identifier from a second word stored in said buffer during a second occurrence in said plurality of occurrences of said subframe; and

(i) comparing said first data set identifier and said second data set identifier to validate said recovered subframe.

13. The method of claim 12, wherein said satellite positioning system satellite comprises a Global Positioning System (GPS) satellite, said navigation data comprises GPS navigation data, and each of said first data set identifier and said second data set identifier comprises an IODE parameter.

14. The method of claim 9, further comprising:

(g) analyzing polarity verification markers in said recovered subframe; and

(h) inverting said recovered subframe in response to said polarity verification markers being inverted.

15. Apparatus for decoding a bitstream of navigation data broadcast by a satellite positioning system satellite, comprising:

a satellite signal receiver for obtaining a portion of a subframe in said navigation data for each of a plurality of occurrences of said subframe in said bitstream to produce a respective plurality of subframe portions;

a memory for storing said plurality of subframe portions; and

a processor for combining said plurality of subframe portions to recover said subframe.

16. The apparatus of claim 15, wherein said processor is configured to process said plurality of subframe portions to maintain a constant polarity.

17. The apparatus of claim 15, wherein said processor is configured to, for each of said plurality of occurrences of said subframe in said bitstream:

decode at least one word from said bitstream;

check parity for each said at least one word; and

store each said at least one word that passes parity in said memory.

18. The apparatus of claim 15, wherein said processor is configured to:

decode a first data set identifier from said bitstream during a first occurrence of said plurality of occurrences of said subframe;

decode a second data set identifier from said bitstream during a second occurrence of said plurality of occurrences of said subframe; and

compare said first data set identifier and said second data set identifier to validate said recovered subframe.

19. The apparatus of claim 18, wherein said satellite positioning system satellite comprises a Global Positioning System (GPS) satellite, said navigation data comprises GPS navigation data, and each of said first data set identifier and said second data set identifier comprises an IODE parameter.

20. The apparatus of claim 15, wherein said processor is configured to:

analyze polarity verification markers in said recovered subframe; and

invert said recovered subframe in response to said polarity verification markers being inverted.

21. Apparatus for decoding a bitstream of navigation data broadcast by a satellite positioning system satellite, comprising:

means for obtaining, at a satellite signal receiver, a portion of a subframe in said navigation data for each of a plurality of occurrences of said subframe in said bitstream to produce a respective plurality of subframe portions; and

means for combining said plurality of subframe portions to recover said subframe.