Impact of Carrier Smoothing on Event Probabilities in LAAS

Curtis A. Shively and Christopher C. Varner

Abstract:	Many performance requirements for the FAA’s Local Area Augmentation System (LAAS) are based on the probability that a random error exceeds a given limit for a certain duration within an exposure time. It was originally believed that carrier smoothing of this error allowed defining the limit as if the exposure time included only one independent error sample. However, recent simulations by Honeywell have shown that if the error is wide-band before carrier smoothing, the above assumption may be incorrect and a larger limit must be associated with the required probability of exceedence during the exposure time. This paper develops a simplified theory that provides a bound on the probability of such events. Three types of probability pertinent to LAAS are examined: 1) probability of fault-free missed detection for H0 protection level, 2) probability of fault- free detection for B value and ranging source monitors and 3) probability of missed detection for ranging source monitors and H1 protection level. This theory corroborates the basic observations made by Honeywell that the event probability is larger than anticipated for probability types 1 and 2, but not for 3. Monte Carlo simulations are also used to confirm results for probability types 1 and 2. The theory is applied to all affected probabilities for both CAT I and CAT III approaches. Since the limit is usually described as Kó, new larger K factors are given where needed.
Published in:	Proceedings of the 58th Annual Meeting of The Institute of Navigation and CIGTF 21st Guidance Test Symposium (2002) June 24 - 26, 2002 Hyatt Regency Hotel Albuquerque, NM
Pages:	195 - 205
Cite this article:	Shively, Curtis A., Varner, Christopher C., "Impact of Carrier Smoothing on Event Probabilities in LAAS," Proceedings of the 58th Annual Meeting of The Institute of Navigation and CIGTF 21st Guidance Test Symposium (2002), Albuquerque, NM, June 2002, pp. 195-205.
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