Method of acquiring satellite data

• US 20070139265A1
• Filed: 11/22/2004
• Published: 06/21/2007
• Est. Priority Date: 12/01/2003
• Status: Active Grant

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Alcatel SA (Nokia Corporation)
• Inventors: Monnerat, Michel
• Granted Patent: US 7,573,423 B2
• Time in Patent Office: Days
• US Class Current: 342/357.680
• CPC Class Codes: G01S 19/25 involving aiding data received from a cooperating element, e.g. assisted GPS
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence

Abstract

The present invention provides a method of acquisition of satellite data by a mobile device including an RNSS satellite radio navigation receiver, said method including the following steps: said receiver receiving a signal transmitted by a plurality of satellites and corresponding to a sum of signals each transmitted by a satellite and each modulated by a spread spectrum signal characteristic of said satellite, said receiver generating a plurality of local duplicates each of which is the duplicate of a spread spectrum signal characteristic of a satellite, correcting the frequency of each of said local duplicates by compensating the Doppler effect of each of said satellites, summing said plurality of corrected duplicates, and determining the correlation function as a function of time between the sum of said plurality of corrected duplicates and said satellite data signal.

Claims

1. A method of acquisition of satellite data by a mobile device including an RNSS satellite radio navigation receiver, said method including the following steps:

said receiver receiving a signal transmitted by a plurality of satellites and corresponding to a sum of signals each transmitted by a satellite and each modulated by a spread spectrum signal characteristic of said satellite,

said receiver generating a plurality of local duplicates each of which is the duplicate of a spread spectrum signal characteristic of a satellite,

correcting the frequency of each of said local duplicates by compensating the Doppler effect of each of said satellites using assistance data sent by an assistance server to said mobile device,

summing said plurality of corrected duplicates, and

determining the correlation function as a function of time between the sum of said plurality of corrected duplicates and said satellite data signal.

2. A method according to claim 1, including identifying each of the satellites associated with each of the correlation peaks revealed by said correlation function.

3. A method according to claim 2, wherein the identification of at least one satellite includes the following steps:

identifying the synchronization time associated with a correlation peak,

determining a plurality of correlations calculated for said synchronization time between each of said corrected duplicates and said satellite data signal, and

identifying the satellite associated with said correlation peak as a function of said correlations.

4. A method according to claim 3, wherein said peak is a main peak of said correlation function as a function of time.

5. A method according to claim 3, wherein, after at least one satellite has been identified, each of the remaining satellites is identified, using assistance data sent to said mobile device from an assistance server, said assistance data including the ephemerides of said satellites and the identifier of the cell in which said mobile device is located, by determining the propagation time difference of a signal between said satellites already identified and said mobile terminal, on the one hand, and each of the satellites to be identified and said mobile device, on the other hand.

6. A method according to claim 2, wherein each of said satellites is identified by the following steps:

identifying the synchronization time associated with a correlation peak,

determining a plurality of correlations calculated for said synchronization time between each of said corrected duplicates and said satellite data signal, and

identifying the satellite associated with said correlation peak as a function of said correlations.

7. A method according to claim 1, wherein said correlation function as a function of time is determined by the following steps:

determining the Fourier transform of each of said corrected duplicates,

summing said Fourier transforms of each of said corrected duplicates,

determining the Fourier transform of said satellite data signal,

multiplying each sum of said Fourier transforms by the Fourier transform of said satellite data signal, and

determining the inverse Fourier transform of the product obtained by the preceding step.

8. An RNSS satellite navigation receiver for implementing the method according to claim 1, said receiver being adapted to receive a signal transmitted by a plurality of satellites and corresponding to a sum of signals each transmitted by a satellite and each modulated by a spread spectrum signal characteristic of said satellite, and said receiver including

means for generating a plurality of local duplicates each of which is the duplicate of a spread spectrum signal characteristic of a satellite,

means for correcting the frequency of each of said local duplicates by compensating the Doppler effect of each of said satellites using assistance data sent by an assistance server to said receiver,

an adder adapted to sum said corrected duplicates, and

means for calculating the correlation function as a function of time between each sum of said corrected duplicates and said satellite data signal.

9. A mobile device incorporating an RNSS satellite navigation receiver according to claim 8.