Method for optimizing an acquisition of a spread-spectrum signal from a satellite by a mobile receiver
First Claim
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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 fi of the signal received at an initial instant t0 and to a trend of the frequency fi over time up to a final instant tn corresponding to an integration time, each assumption in the plurality of assumptions relating to the trend of the frequency fi of the signal between the initial instant t0 and the final instant tn being a trend path;
calculating a plurality of correlation functions s(fi, tk, τ
) of all pairs of frequency-time assumptions (fi, tk) using at least the local replica;
choosing a first initial frequency assumption f1 out of the plurality off assumptions relating to the frequency fi 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 tn, the total energy of each possible trend path being obtained by coherently aggregating correlation results between the initial t0 and final tn 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 fi 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 fi, the trend path which has the strongest energy is the most likely path and substantially corresponds to a real path followed by the receiver.
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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.
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Citations
6 Claims
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1. A method for optimizing an acquisition of a spread-spectrum signal originating from a satellite by a mobile receiver, said method comprising:
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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 fi of the signal received at an initial instant t0 and to a trend of the frequency fi over time up to a final instant tn corresponding to an integration time, each assumption in the plurality of assumptions relating to the trend of the frequency fi of the signal between the initial instant t0 and the final instant tn being a trend path; calculating a plurality of correlation functions s(fi, tk, τ
) of all pairs of frequency-time assumptions (fi, tk) using at least the local replica;choosing a first initial frequency assumption f1 out of the plurality off assumptions relating to the frequency fi 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 tn, the total energy of each possible trend path being obtained by coherently aggregating correlation results between the initial t0 and final tn 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 fi 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 fi, the trend path which has the strongest energy is the most likely path and substantially corresponds to a real path followed by the receiver. - View Dependent Claims (2, 3, 4, 5)
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6. A method for optimizing an acquisition of a spread-spectrum signal originating from a satellite by a mobile receiver, said method comprising:
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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 fi of the signal received at an initial instant t0 and to a trend of the frequency fi over time up to a final instant tn corresponding to an integration time, each assumption in the plurality of assumptions relating to the trend of the frequency fi of the signal between the initial instant t0 and the final instant tn being a trend path; calculating a plurality of correlation functions s(fi, tk, τ
) of all pairs of frequency-time assumptions (fi, tk) using at least the local replica;choosing a first initial frequency assumption f1 out of the plurality of assumptions relating to the frequency fi 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 tn, the total energy of each possible trend path being obtained by coherently aggregating correlation results between the initial t0 and final tn 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 fi 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 fi, 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.
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Specification