SOURCEFORGE » RALF » 2015 Software defined GPS receiver

h1. PART 5 : Implementation.

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h2. 1 - Starting point.

h3. a - Receiver scheme and milestones.

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h3. b - Quid about LabVIEW.

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Input : GPS signal of sampling frequency 38.192 MHz at intermediate frequency 9.55 MHz from CD *[1]* under GNSS_signal_records/GPSdata-DiscreteComponents-fs38_192-if9_55.bin

h3. c - Local C/A code generation.

Generation : _CA_code.vi_ with subVI _CA_generatorG1.vi_ _CA_generatorG2.vi_

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h2. 2 - Acquisition.

Justification acquisition method in terms of accuracy and time execution
Justification of the step of 500Hz
Methods to avoid the data bit transition while running acquisition
Frequency refine is needed for the PLL of the tracking to converge
Definition of the threshold and how it is implemented

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h2. 3 - Tracking.

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p=. !TrackingMin.PNG!

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h2. 4 - Navigation Data decoding.

*See the UML Diagram of Section 4 under :* attachment:"NavigationData.PNG".

h3. a - Delimiting subframes.

The files involved are :
- _FindPreamble.vi_
- _TestFindPreamble.vi_
- _GenerateFrame.vi_
- _ParityCheck.vi_

p=. !Preamble1.PNG! !Preamble2.PNG!

p((((. *Figure 5. :* Cross-correlation between navigation frame and local preamble. *Figure 5. :* Subframes with index of delimitation.



h3. b- Decoding ephemeris and information within the frame.

The files involved are :
- _Ephemeris.vi_
- _BinaryArrayToDecimal.vi_
- _twosComp2dec.vi_
- _ParityCheck.vi_
- _TestEphemeris.vi_

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h2. 5 - Localization computation.

*See the UML Diagram of Section 5 under :* attachment:"Localization.PNG"

h3. a - Satellite position.

The files involved are :
- _SatellitePosition.vi_
- _TestSatellitePosition.vi_
- _Check_time.vi_

p=. !SatPos.PNG!
*Figure 5. :* Interface with ephemeris as input and illustration of the satellite position.

h3. b - Pseudoranges.

The file involved is :
_PseudorangesComputation.vi_

h3. c - Least Square solution for position determination.

The files involved are :
- _LeastSquarePosition.vi_
- _SatelliteRotationECEF.vi_
- _toTopocentric.vi_
- _CartesianToGeodetic.vi_
- _TroposphericCorrection.vi_

h2. 6 - Complete UML Diagram of the receiver.

!UMLDiagram.png!

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*References :*
*[1]* K. Borre, D. M. Akos, N. Bertelsen, P. Rinder, S. H. Jensen, A software-defined GPS and GALILEO receiver