Cross-correlation system for time recovery in network-assisted GPS positioning
First Claim
1. A method for determining the time at which a satellite vehicle (SV) signal received by a mobile receiver was broadcast by the SV, the SV signal having been de-spread and approximately demodulated but including some residual modulation, the mobile receiver being located in the coverage area of a station of a wireless communication system, the method comprising the steps of:
- a) having a correlator of the mobile receiver be provided with the SV signal;
b) having the station provide to the mobile receiver the content of at least a portion of the same SV signal;
c) having the mobile receiver perform a correlation of the SV signal with a replica of at least a portion of the SV signal determined from the content of a portion of the SV signal provided by the station; and
d) determining the time at which the signal was broadcast by the SV on the basis of the correlation;
wherein the correlation is performed in a way that accounts for any residual modulation of the SV signal by an operation that involves multiplying the SV signal by sinusoids or approximated sinusoids at discrete frequencies spanning a range that encompasses the frequency of the residual modulation.
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Accused Products
Abstract
A method and apparatus for measuring time related to satellite navigation data messages used with a satellite-based global positioning systems (GPS). A first record of at least a portion of a satellite data message is received at an entity, which is typically a base station of a wireless communication system. The first record is compared with a second record of the same satellite data message (navigation message) received by a GPS receiver. From the comparison, a time is determined indicating when the satellite date message was transmitted (broadcast). The comparison is made in a way that accounts for the only approximate removal of all modulation of the satellite data message by the acquisition and tracking stages of the GPS receiver.
30 Citations
24 Claims
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1. A method for determining the time at which a satellite vehicle (SV) signal received by a mobile receiver was broadcast by the SV, the SV signal having been de-spread and approximately demodulated but including some residual modulation, the mobile receiver being located in the coverage area of a station of a wireless communication system, the method comprising the steps of:
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a) having a correlator of the mobile receiver be provided with the SV signal;
b) having the station provide to the mobile receiver the content of at least a portion of the same SV signal;
c) having the mobile receiver perform a correlation of the SV signal with a replica of at least a portion of the SV signal determined from the content of a portion of the SV signal provided by the station; and
d) determining the time at which the signal was broadcast by the SV on the basis of the correlation;
wherein the correlation is performed in a way that accounts for any residual modulation of the SV signal by an operation that involves multiplying the SV signal by sinusoids or approximated sinusoids at discrete frequencies spanning a range that encompasses the frequency of the residual modulation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An apparatus for determining the time at which a satellite vehicle (SV) signal received by a mobile receiver was broadcast by the SV, the SV signal having been de-spread and approximately demodulated but including some residual modulation, the mobile receiver being located in the coverage area of a station of a wireless communication system, the apparatus comprising:
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a) means for providing the SV signal to a correlator of the mobile receiver;
b) means for receiving from the station the content of at least a portion of the same SV signal;
c) means for having the mobile receiver perform a correlation of the SV signal with a replica of at least a portion of the SV signal determined from the content of a portion of the SV signal provided by the station; and
d) means for determining the time at which the signal was broadcast by the SV on the basis of the correlation;
wherein the correlation is performed in a way that accounts for any residual modulation of the SV signal by an operation that involves multiplying the SV signal sinusoids or approximated sinusoids at discrete frequencies spanning a range that encompasses the frequency of the residual modulation. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A system, comprising:
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a) an apparatus for determining the time at which a satellite vehicle (SV) signal received by a mobile receiver was broadcast by the SV, the SV signal having been de-spread and approximately demodulated but including some residual modulation, the mobile receiver being located in the coverage area of a station of a wireless communication system, the apparatus comprising;
i) means for providing the SV signal to a correlator of the mobile receiver;
ii) means for receiving from the station the content of at least a portion of the same SV signal;
iii) means for having the mobile receiver perform a correlation of the SV signal with a replica of at least a portion of the SV signal determined from the content of a portion of the SV signal provided by the station;
iv) means for determining the time at which the signal was broadcast by the SV on the basis of the correlation; and
wherein the correlation is performed in a way that accounts for any residual modulation of the SV signal by an operation that involves multiplying the SV signal by sinusoids or approximated sinusoids at discrete frequencies spanning a range that encompasses the frequency of the residual modulation; and b) a station, responsive to the same SV signal as the mobile receiver, for providing the content of at least a portion of the same SV signal as received by the mobile receiver. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
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Specification