Enhancing GPS Timing Engines Using WAAS Signals

摘要

Accurate timing sources are becoming a very important issue in the development of networked telecommunication systems. Since the early 1990's, GPS has been exploited for this purpose. The common GPS time transfer technique is mostly used to minimize the timing error caused by satellite clock and ephemeris errors, and Selective Availability. This technique provides a typical timing accuracy of 50 nanoseconds (I sigma). Currently, a new WAAS (Wide Area Augmentation System) is being developed under the authority of the FAA (Federal Aviation Administration). This system is a Satellite-Based Augmentation System (SBAS) which will be used to enhance signal continuity, availability, and integrity to GPS receivers. WAAS is scheduled to be officially commissioned in the summer of 2000. This paper describes the features and performance of a GPS/WAAS Timing Engine developed by Marconi Canada. The paper will discuss the features of the WAAS system and how it can be used to dramatically decrease the timing errors of a GPS engine. Results obtained using a GPS simulator and live signals will be analyzed. Comparative results between a GPS only and a GPS/WAAS Timing Engine will be presented. Finally, additional features of the GPS/WAAS Timing Engine, such as TRAIM (Time Remote Autonomous Integrity Monitoring), will be discussed.