GPS PRN Code Assignment Process

摘要

The Global Positioning System (GPS) is a spreadspectrum system that employs direct-sequence spreading of the spectrum to achieve better ranging accuracy. Although GPS was originally conceived for use by the military in their missions, it has become an important utility for a number of civil and commercial applications. To facilitate improvement in the use of satellite navigation by the civilian users, for example, aviation and terrestrial transportation systems, additional spreadspectrum signals called L1C, L2C, and L5 are being added to the current GPS signals. All these signals use spreading codes to spread the spectrum. Also, a number of GPS augmentation systems by a number of different administrations already exist or are being planned that use GPS-like spreading codes. Therefore, it has become very important to assign the GPS spreading codes to various GPS augmentation systems in a systematic way to avoid code duplication and using codes with poor properties that may interfere with the GPS receiver performance. The GPS Wing (GPSW) has the responsibility to assign pseudorandom noise (PRN) codes for various GPSrelated augmentation systems for all the GPS signals. The GPSW is also involved in the selection of good codes, which is the first step in the code assignment process. rnAn important consideration in the design of a spreadspectrum signal for Code Division Multiple Access (CDMA) applications such as in GPS is to select codes to minimize what is known as CDMA noise. The code selection process can be very tedious, depending on the number of codes needed and the number of codes available in a given code set. Code balance, autocorrelation sidelobe peak, cross-correlation peak, and spectral line distributions are some of the measures available in the code selection process, and these measures are not necessarily independent. rnIn this paper we give a brief description of the spreading pseudorandom noise (PRN) code assignment process is given that may be very useful for those contemplating the use of GPS-like codes in their augmentation systems.