![]() :param list output: which positions are output (1 indexed) :param list feedback: which positions to use as feedback (1 indexed) Taking it step by step:ĭef shift ( register, feedback, output ): """GPS Shift Register We’ll start them out with all 1’s, calculate the feedback, and then shift all the numbers over to the right. Let’s make a software emulation of a shift register in python! A shift register is just a list of bits that has an input end and an output end. The Gold Codes are generated using a pair of shift registers with feedback. This is the scheme used to create pseudo-random sequences with all these properties for GPS: Shift Registers We also want the different codes for each satellite that are nearly orthogonal so the cross correlation of one code will be very high even when many satellite codes are mixed in. It also helps the spreading properties.Ī signal that’s statistically random doesn’t repeat itself at any point in its sequence and so it has very good autocorrelation properties. One of the reasons you want a spreading code that looks random is to ensure you have good autocorrelation properties. ![]() In fact, it’s not random, it’s a kind of pseudo-random number. But they don’t just use any random number. PRN (“Psuedo Random Noise”) sequences are used as part of the CDMA scheme in GPS. The GPS PRN (Gold Codes) natronics on GitHub The GPS PRN (Gold Codes) – September 2014 The GPS PRN (Gold Codes)įirst read the previous post about the basics of GPS encoding. ![]()
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