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Posted 2/22/2016 Printable Fact Sheet
Global Positioning System (GPS) Block IIR (Image courtesy of Lockheed-Martin for Department of Defense and media publications; use for commercial purposes is prohibited.)
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The Global Positioning System (GPS) is a spread-spectrum system that employs direct-sequence code spreading to achieve increased accuracy for position, navigation, and timing (PNT). Although GPS was originally conceived for military applications, it has become a key utility for a plethora of civil and commercial applications. To facilitate improvement in the use of satellite navigation by the civilian users (e.g. aviation and terrestrial transportation systems), the U.S. Air Force is adding the L2C, L5, and L1C signals to the GPS constellation in addition to the existing L1 C/A code. Both the existing and new signals use spreading codes called Pseudorandom Noise (PRN) codes. Also, a number of GPS augmentation systems already exist or are being planned that use GPS-like spreading codes. Therefore, it has become essential to assign the GPS spreading codes to various GPS augmentation systems in a systematic way to avoid code duplication and/or using codes with poor properties that may interfere with GPS receiver performance.

PRN Code Assignment Process

Many domestic and international radionavigation systems seek a high level of interoperability with GPS, including the use of PRN codes from the spreading code families developed for GPS. Signals that employ PRN codes from the GPS spreading code families achieve an established level of code performance, including a level of interoperability with GPS signals. Additionally, the use of pre-defined GPS-based PRN codes fosters the development of receivers capable of seamlessly using signals from more than one radionavigation system. The resulting interoperability is beneficial to all systems using GPS-based PRN codes. As part of its acquisition and sustainment effort for GPS, the GPS Directorate manages the coordination and issuance of PRN codes. For this purpose, a large set of PRN codes providing favorable auto-correlation and cross-correlation properties have been pre-defined, and the GPS Directorate will select and issue PRN codes from this set.

The PRN Number Assignment Process document (linked below) describes the process for requesting, assigning, and relinquishing the GPS-based PRN codes pre-defined in GPS interface specifications IS-GPS-200, IS-GPS-705, and IS-GPS-800. PRN numbers currently assigned and PRN numbers currently available for assignment can be found in the L1 C/A, L2C, L5, and L1C PRN code assignments tables linked below. 

Application for PRN Number Assignment

To request one or more PRN code assignments, applicants must provide the identification and system information by filling out the "Application for PRN Number Assignment" linked below. Once the application is complete, the applicant should email the application to the GPS Directorate at smc.gp.prn@us.af.mil. During the PRN number assignment process, the GPS Directorate will review the submitted data and may request additional information. The assignment process generally will require three to six weeks following proper submission of all required information. If the review results are satisfactory, the GPS Directorate will issue a PRN Number Assignment. The assignment may be either Preliminary (expires in 3 years) or Final (expires in 10 years), and the applicant may renew the assigned PRN Number Assignment prior to the expiration. If there are concerns about mutual interference or other interactions, the GPS Directorate will contact the applicant(s) to initiate more detailed discussions.

Applicants can contact the directorate with any comments or questions at smc.gp.prn@losangeles.af.mil.

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