WAAS Avionics Receiver Design Characteristics

Rajendra Kumar, Prem Munjal, K. T. Woo, and Henry Yeh

Abstract:	The application of Global Positioning System (GPS) signals as a primary navigation aid for civil aviation has recently received great national and international attention. With the Wide Area Augmentation System (WAAS) under development by the Federal Aviation Administration, this application will soon become a reality. Augmentation signals from geostationary satellites, combined with signals from the GPS constellation, will be able to guide aircraft navigation in all phases of flight including en route, terminal, nonprecision and precision approach, replacing the more costly landing systems such as the Instrument Landing System (ILS) and Microwave Landing Systems (MLS). Detailed design study of the WAAS system and receiver has been performed by RTCA SC- 159 Working Group 2. This paper highlights some of the design issues pertaining to the WAAS receiver. Specifically the paper summarizes the key design considerations of the WAAS avionics receiver that receives ranging signals and navigation messages from WAAS geostationary satellites and GPS satellites in view. Key differences, for example, between WAAS and GPS signals are message data rates and forward error correction encoding. Such differences affect WAAS avionics receiver in its data demodulation functions. In addition, WAAS availability requirements in accuracy, integrity, continuity of function, and message latency demand certain signal processing functions unique to the WAAS avionics receiver. These functions include weighted navigation solution, processing of WAAS error correction messages, autonomous fault detection and exclusion, RF interference and multipath mitigation, and total system error warning: all essential parts of the primary-means navigation receiver. A summary of performance parameters according to equipment classification is given. In addition, possible areas of design enhancements for end-state WAAS applications are identified. Discussions on WAAS receiver integrity processing and interference rejection requirements are based on the Minimum Operational Performance Standards (MOPS) developed by RTCA SC-159. It should be noted that these standards are not final and the requirements reported here may change when the standards are updated.
Published in:	Proceedings of the 1996 National Technical Meeting of The Institute of Navigation January 22 - 24, 1996 Loews Santa Monica Hotel Santa Monica, CA
Pages:	639 - 654
Cite this article:	Kumar, Rajendra, Munjal, Prem, Woo, K. T., Yeh, Henry, "WAAS Avionics Receiver Design Characteristics," Proceedings of the 1996 National Technical Meeting of The Institute of Navigation, Santa Monica, CA, January 1996, pp. 639-654.
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