Analysis of Proposed GPS Signal Structures for Use in ARNS Bands

A. J. Van Dierendonck, Patrick Reddan

Abstract:	The general consensus in the Department of Transportation and in the aviation community is that a second protected GPS frequency is needed but in an Aeronautical Radio Navigation Services frequency band. A civil signal at the GPS L2 frequency band would not be adequate since that frequency is not only used by GPS, but by other systems (primarily radar systems), and it is not a band protected for aeronautical applications. When considering signal structures for a civil signal in the L2 band as part of the process to determine the frequency location of the civil signal, we were restricted to coexist with the existing and future GPS military signals. Thus, only the C/A code or variations of the C/A code (Split C/A code, for example) were considered for L2. However, once we move to a new band allocated for aeronautical use, this restriction no longer applies. In the past, the civil community, including aviation, has been very innovative in extracting as much performance as possible out of the C/A code at L1. Most of this performance is realized by tracking the code transition "edges" (or spectral side-lobes) that requires as much bandwidth (up to 20 MHz) as possible. In reality, however, the C/A code is not very spectrally efficient, because most of its energy is within 2 MHz of the center frequency. Thus, it makes sense to investigate the use of wider bandwidth codes that are more spectrally efficient. This could include a narrower band version of the much analyzed Split C/A code, as well as longer, higher chipping rate, codes. Preliminary investigations have occurred, both for split C/A codes and for longer Gold-codes, and it has been found that these codes, limited to bandwidths of 20 MHz, can provide superior performance relative to the wide bandwidth C/A code. The results of this analysis along with signal structure recommendations will be presented in this paper.
Published in:	Proceedings of the 1999 National Technical Meeting of The Institute of Navigation January 25 - 27, 1999 Catamaran Resort Hotel San Diego, CA
Pages:	661 - 669
Cite this article:	Van Dierendonck, A. J., Reddan, Patrick, "Analysis of Proposed GPS Signal Structures for Use in ARNS Bands," Proceedings of the 1999 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 1999, pp. 661-669.
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