Current GPS Constellation and Signal Structure Overview

Wednesday, August 16, 2000 - 9:35am - 10:05am
Keller 3-180
A.J. Van Dierendonck (AJ Systems)
In the next 5 to 10 years, GPS will be adding new civil signals to enhance GPS performance for civil users ­ a C/A code signal at the L2 frequency and a very robust wide bandwidth signal at L5 (1176.45 MHz). These new signals, when combined with the existing C/A code signal at the L1 frequency, will certainly provide an enhanced carrier phase ambiguity resolution capability. Surely, others participating in this workshop will be addressing that subject in detail. In this presentation, we will lay the groundwork for those discussions by describing these new signals and the enhanced multipath mitigation capabilities using the new L5 signal. In addition, enhanced capabilities for operating in adverse environments (foliage, etc.) will be discussed.

One challenge we face in using these new signals is to be able to use them at the earliest possible date. After all satellites are broadcasting these new signals, it will be relatively easy to exploit them. However, these new signals will be phased in over a number of years as older satellites fail. So, how do we take advantage of them in the interim, especially early in their deployment?

The US DoD is currently entering a procurement stage for GPS III, starting with studies investigating what other enhancements could be added to GPS to improve performance. These possible enhancements also include those for civil users. They will be soliciting ideas for these (reasonable) enhancements. This presents another challenge. That is, what enhancements can be reasonably added that would benefit civil users? The mathematical challenge is one of performance evaluation of those ideas. Possible GPS III enhancements will be discussed along with a list of enhancements that are not probable (for example, no more new signals).