Method for optimizing an acquisition of a spread-spectrum signal from a satellite by a mobile receiver

• US 8,472,504 B2
• Filed: 09/25/2009
• Issued: 06/25/2013
• Est. Priority Date: 09/26/2008
• Status: Active Grant

• Current Assignee: Centre National D'Etudes Spatiales, Thales SA
• Original Assignee: Centre National D'Etudes Spatiales, Thales SA
• Inventors: Monnerat, Michel, Ries, Lionel, Kubrak, Damien, Artaud, Graldine
• Primary Examiner(s): Puente, Eva
• Application Number:
  US13/121,066
• Publication Number:
  US 20110206090A1
• Time in Patent Office: 1,369 Days
• Field of Search: 375/142, 375/147, 375/150, 375/343, 342/357.12
• US Class Current: 375/142
• CPC Class Codes: G01S 19/26 involving a sensor measurement for aiding acquisition or tracking
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence
• CPC Class Codes: H04B 1/7075 with code phase acquisition
• CPC Class Codes: H04B 2201/70715 with application-specific features

Abstract

A method for optimizing an acquisition phase of a spread-spectrum signal by a mobile receiver includes searching for a trend path having the maximum energy for different frequency assumptions and among all the positive trend paths of frequencies between initial and final instants marking the beginning and the end of a coherent signal integration.

Claims

1. A method for optimizing an acquisition of a spread-spectrum signal originating from a satellite by a mobile receiver, said method comprising:

receiving a signal transmitted by at least one transmitter, the signal being modulated by a pseudo-random code;

generating a local replica of the pseudo-random code of the signal transmitted;

determining a plurality of assumptions relating to a frequency f_i of the signal received at an initial instant t₀ and to a trend of the frequency f_i over time up to a final instant t_n corresponding to an integration time, each assumption in the plurality of assumptions relating to the trend of the frequency f_i of the signal between the initial instant t₀ and the final instant t_n being a trend path;

calculating a plurality of correlation functions s(f_i, t_k, τ

) of all pairs of frequency-time assumptions (f_i, t_k) using at least the local replica;

choosing a first initial frequency assumption f₁ out of the plurality off assumptions relating to the frequency f_i corresponding to the initial instant t₀;

acquiring at least one information item concerning the movement of the receiver, and deducing therefrom, for the first initial frequency assumption f₁, the trend assumptions for a frequency of the signal over time;

determining a respective total energy, corresponding to a maximum of the correlation function, as a correlation peak, of all the possible trend paths of the frequency of the signal between the instants t₀ and t_n, the total energy of each possible trend path being obtained by coherently aggregating correlation results between the initial t₀ and final t_n instants, the frequency taking in succession all the frequency values located on the chosen trend path;

selecting the trend path whose total energy is the strongest;

choosing in succession all the other remaining possible initial frequency assumptions in the plurality of assumptions relating to the frequency f_i and, for each remaining initial frequency assumption, selecting the trend path whose total energy is the strongest; and

deciding that, out of all the trend paths selected on each frequency assumption in the plurality of assumptions relating to the frequency f_i, the trend path which has the strongest energy is the most likely path and substantially corresponds to a real path followed by the receiver.

2. The method as claimed in claim 1, wherein the total energy of each possible trend path of the frequency of the signal is obtained by coherently aggregating the correlation results between the initial instant t₀ and final instant t_n, the frequency successively taking all the frequency values located on the chosen path.

3. The method as claimed in claim 1, wherein, for each initial frequency assumption, the possible trend paths of the frequency of the signal are determined by taking into account information delivered by at least one inertial sensor located in the receiver.

4. The method as claimed in claim 3, wherein the information delivered by the inertial sensor is taken into account in an error envelope established on the basis of the characteristics of the sensor.

5. The method as claimed in claim 4, wherein, when the variation of the information delivered by the sensor, between two measurement instants, is below a predetermined variation threshold, it is decided that the receiver has not moved between the two measurement instants and a frequency that is stable during integration is then assumed.

6. A method for optimizing an acquisition of a spread-spectrum signal originating from a satellite by a mobile receiver, said method comprising:

receiving a signal transmitted by at least one transmitter, the signal being modulated by a pseudo-random code;

generating a local replica of the pseudo-random code of the signal transmitted;

determining a plurality of assumptions relating to frequency f_i of the signal received at an initial instant t₀ and to a trend of the frequency f_i over time up to a final instant t_n corresponding to an integration time, each assumption in the plurality of assumptions relating to the trend of the frequency f_i of the signal between the initial instant t₀ and the final instant t_n being a trend path;

calculating a plurality of correlation functions s(f_i, t_k, τ

) of all pairs of frequency-time assumptions (f_i, t_k) using at least the local replica;

choosing a first initial frequency assumption f₁ out of the plurality of assumptions relating to the frequency f_i corresponding to the initial instant t₀;

acquiring at least one information item concerning the movement of the receiver, and deducing therefrom, for the first initial frequency assumption f₁, the trend assumptions for a frequency of the signal over time;

determining a respective total energy, corresponding to a maximum of the correlation function, as a correlation peak, of all the possible trend paths of the frequency of the signal between the instants t₀ and t_n, the total energy of each possible trend path being obtained by coherently aggregating correlation results between the initial t₀ and final t_n instants, the frequency taking in succession all the frequent values located on the chosen trend path;

selecting the trend path whose total energy is the strongest;

choosing in succession all the remaining possible initial frequency assumptions in the plurality of assumptions relating to the frequency f_i and, for each remaining initial frequency assumption, selecting the trend path whose total energy is the strongest; and

deciding that, out of all the trend paths selected on each frequency assumption in the plurality of assumptions relating to the frequency f_i, the trend path which has the strongest energy is the most likely path and substantially corresponds to a real path followed by the receiver, wherein, for each initial frequency assumption, the possible trend paths of the frequency of the signal are determined by taking into account information delivered by at least one inertial sensor located in the receiver.