Information about Global Positioning System (GPS) Pseudorandom Noise (PRN) codes and the PRN Code Assignment process, including related documents, can be found at https://www.gps.gov/technical/prn-codes/.
Overview
The Global Positioning System is a spread-spectrum system that employs direct-sequence spreading of the L-band carrier signals broadcast by each transmitter. The direct sequences used for the broadcast Standard Positioning Service (SPS) signals – that is, the L1 C/A, L1C, L2C, and L5 signals – are all pre-defined repeating pseudorandom noise (PRN) codes.
Many domestic and international radionavigation aids, including Satellite-Based Augmentation Systems (SBASs), seek high levels of interoperability with GPS. In the extreme, this means broadcasting SPS-like signals that include the use of PRN codes from the same PRN code families developed for GPS signals. Therefore, it has become important to assign GPS PRN codes to various GPS augmentation systems in a systematic way to prevent PRN code duplication and avoid using codes with poor properties that may interfere with receiver performance.
Signals that employ GPS PRN codes achieve an established level of code performance, including good compatibility with all other signals using GPS PRN codes. In addition, receivers can more readily generate and use all the PRN codes, thus fostering receivers that can use all signals. The resulting compatibility and interoperability are mutually beneficial to all systems using GPS PRN codes.