Method for delivering secondary (non-location) data to a GPS receiver
AssigneeSouthwest Research Institute
InventorsJennifer L. Alvarez, Roger R. Chiodo, Thomas H. Jaeckle
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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.
Claims20
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 GPS 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.
A improved GPS receiver for receiving secondary data, using only GPS hardware including a GPS processing unit, the improvement comprising:
- a processing unit programmed to search for a signal having a specified GPS frequency at a specified time, and with a GPS 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.
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:
- programming the processing unit to search for a signal having a specified GPS frequency at a specified time, and with a GPS 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.
Dependencies are inferred from the claim text.