Design and Implementation of a SoftwareBased GPS Receiver
Design and Implementation of a Software-Based GPS Receiver Anthony J. Corbin Dr. In Soo Ahn Thursday, September 23, 2021
Project Summary o Software-Based Solution n n Advantages o Size o Cost o Portability Implementation o Sampling System n n o Downconverter A/D Converter DSP System n Simulates a microcontroller
Patents o o o The table below lists relevant patents. Most of the patents are recent. Notably, two of the patents were granted to Denso and Toyota.
Referenced Work o Kai Borre, Dennis M. Akos, Nicolaj Bertelsen, Peter Rinder, and Soren Holdt Jensent, Software-Defined GPS and Galileo Receiver : A Single-Frequency Approach. Birkhauser: Boston, 2007, pp. 29, 83, 105.
Goals o o o Implement a software GPS L 1 signal model Develop a software-based GPS receiver model for processing a sample input dataset Implement the model in a high-level language such as C++ Process the raw data using an embedded system or DSP kit using the model developed Connect the embedded system or DSP kit to a sampling device and perform satellite signal acquisition Compute position in real-time
High-Level Block Diagram
SE 4110 o Functions n n n o LNA Downconverter A/D Converter Output n n n Reference Clock Sign Bit Magnitude Bit
DSP Kit o o 225 MHz 2 MCBSPs n o Multi-Channel Buffered Serial Ports 16 Megabytes of RAM
![Software Processing [1]](http://slidetodoc.com/presentation_image_h2/bcb869e209b5ab2a1d853a3da8cc614d/image-9.jpg "Software Processing [1]")
Software Processing [1]
Subsystem Requirements
Position Error o o Estimated position is based on the sampling rate being 4 times the chipping rate. ¼ of the distance represented by a chip is therefore the approximate error.
Time to First Fix o o A position fix requires that the ephemeris data is completely received. This requires a complete frame of data, which takes 30 s to transmit. However, it is unlikely that the receiver shall begin collecting data at the beginning of a subframe indicating that an extra subframe lasting 6 s must be received. If the ephemeris data has already been received, the fix time is minimal. [1]
Display o The display shall be relatively simple providing: n n n Latitude, Longitude, and Altitude Earth-Centered, Earth-Fixed Coordinates (Relative) UTC Time o Local time correction may be selected
L 1 Signal Generation o o A generated L 1 sample is shown to the right. The signal generated is based on the pseudorandom sequence generation shown on the next slide.
![L 1 Signal Generation [1]](http://slidetodoc.com/presentation_image_h2/bcb869e209b5ab2a1d853a3da8cc614d/image-15.jpg "L 1 Signal Generation [1]")
L 1 Signal Generation [1]
Cross-Correlation o o o The cross-correlation characteristics of the L 1 signal are what make it important. Different L 1 signals do not correlate with each other! The figure to the right shows a graphical representation of the plane of all correlation possibilities.
Preliminary Measurements o o The GPS L 1 signal is attenuated to a level below the noise floor. The graph on the right shows the result of an FFT of the data from the SE 4110 L device.
Equipment List
Preliminary Schedule
![References o o o [1] Kai Borre, Dennis M. Akos, Nicolaj Bertelsen, Peter Rinder,](http://slidetodoc.com/presentation_image_h2/bcb869e209b5ab2a1d853a3da8cc614d/image-20.jpg "References o o o [1] Kai Borre, Dennis M. Akos, Nicolaj Bertelsen, Peter Rinder,")
References o o o [1] Kai Borre, Dennis M. Akos, Nicolaj Bertelsen, Peter Rinder, and Soren Holdt Jensent, Software-Defined GPS and Galileo Receiver : A Single-Frequency Approach. Birkhauser: Boston, 2007, pp. 29, 83, 105. [2] Si. Ge, SE 4110 L-EK 1 Evaluation Board User Guide. [3] Si. Ge, SE 4110 L Datasheet. [4] Wikipedia, “Global Positioning System” [online], available from World Wide Web: <http: //en. wikipedia. org/wiki/Global_Positioning_System>. [5] Si. RF, “Si. RFstar. III GSD 3 t” [online], available from World Wide Web: < http: //www. sirf. com/products/gps_chip 2 e. html>.
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