Method for delivering secondary (non-location) data to a GPS receiver
First Claim
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1. A method of communicating secondary data to a GPS receiver having only GPS hardware, comprising the steps of:
- controlling the GPS receiver to search for a specified GPS frequency at a specified time, and with a spreading code;
transmitting a secondary data signal that conforms to frequency and data rate characteristics of a GPS signal;
wherein the secondary data signal has subframes having the same format as a GPS navigation data signal except for a portion of the bits within a portion of the words of the subframe, said portion of the bits comprising the secondary data;
receiving and demodulating the secondary data signal at the GPS receiver; and
providing instructions to the processor of the GPS receiver for processing the secondary data.
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Abstract
A method of using a GPS receiver to receive secondary data. A conventional GPS receiver is modified to receive such data, without modifying its hardware. The secondary data is carried in a signal that has the same characteristics as a conventional GPS navigation signal, but is delivered at a specified frequency and time and with a specified and “unused” spreading code. The secondary data is contained in a data subframe that is sufficiently similar to subframes that carry GPS navigation data, such that it can be demodulated and accessed by the GPS receiver.
28 Citations
20 Claims
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1. A method of communicating secondary data to a GPS receiver having only GPS hardware, comprising the steps of:
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controlling the GPS receiver to search for a specified GPS frequency at a specified time, and with a spreading code;
transmitting a secondary data signal that conforms to frequency and data rate characteristics of a GPS signal;
wherein the secondary data signal has subframes having the same format as a GPS navigation data signal except for a portion of the bits within a portion of the words of the subframe, said portion of the bits comprising the secondary data;
receiving and demodulating the secondary data signal at the GPS receiver; and
providing instructions to the processor of the GPS receiver for processing the secondary data. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A improved GPS receiver for receiving secondary data, using only GPS hardware including a GPS processing unit, the improvement comprising:
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a processing unit programmed to search for a signal having a specified GPS frequency at a specified time, and with a spreading code;
wherein the signal conforms to frequency and data rate characteristics of a GPS signal, but is a secondary data signal having subframes having the same subframe format as a GPS signal except for a portion of the bits within a portion of the words of the subframe, said portion of the bits comprising the secondary data; and
the processing unit further programmed to lock to the spreading code, to track the carrier signal, to synchronize the subframe, and to access the data bits within the subframe. - View Dependent Claims (12, 13, 14)
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15. A method of modifying a GPS receiver having a processing unit so that the GPS receiver may receive secondary message data, comprising the steps of:
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programming the processing unit to search for a signal having a specified GPS frequency at a specified time, and with a spreading code;
wherein the signal conforms to frequency and data rate characteristics of a GPS signal, but is a secondary data signal having subframes having the same subframe format as a GPS signal except for a portion of the bits within a portion of the words of the subframe, said portion of the bits comprising the secondary data;
further programming the processing unit to lock to the spreading code, to track the carrier signal, to synchronize the subframe, and to access the secondary data bits within the subframe. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification