Mitigation of Code-carrier Divergence Effect using an Optimized Filter for LAAS Applications

Abstract

Local Area Augmentation System (LAAS) is an augmentation to GPS, for providing aircraft precision approach and landing. LAAS relies on Hatch Alter for code smoothing but its Altered range is affected by code-carrier divergence occurring during ionospheric storms. Substituting traditional Hatch filter by optimized filter reduces this effect to a considerable extent. The objective of this paper is to estimate code-carrier divergence and mitigate it using the optimized filter. The performance of both Hatch and optimized filters is analyzed for different ionosphere conditions such as the geomagnetic storm of October 2003 over a low latitude station. Investigations showed that the optimized filter outperforms Hatch Filter for disturbed day data, whereas for quiet day data, it does not provide any additional advantage. The results obtained are agreeing with the results published elsewhere and are encouraging.

Keywords:

• Code-carrier divergence
• GPS
• Hatch filter
• Local area augmentation system
• Optimized filter
• RINEX

Additional information

Notes on contributors

A. Supraja Reddy

A. Supraja Reddy obtained her B.E degree from Osmania University, M.Tech from JNTUH, Hyderabad and is pursuing Ph.D at JNTUK, Kakinada. Her research interests include GPS, GBAS and Atmospheric Constraints on GPS aided Navigation. She has about eight years of teaching experience. Presently she is working as Research Scientist/Scientist-B at Research and Training Unit for Navigational Electronics (NERTU), Osmania University, Hyderabad. E-mail: [email protected]

G. Santhosh Kumar

G. Santhosh Kumar received B.Tech in Electronics & Communication Engineering from JNTUH, Hyderabad and M.E in Microwave & Radar Engineering from Osmania University, Hyderabad. His areas of interest include GPS and GIS. E-mail: [email protected]

A. D. Sarma

A. D. Sarma was born in Achanta, India, in August 1953. He received the Ph.D. degree in electronic and electrical engineering from London University, London, U.K., in 1986. He was associated with Defence Electronics Application Laboratory, Defence Research and Development Organization, Dehradun, India; Electrical Engineering Department, Indian Institute of Technology Delhi, New Delhi, India; Defence Electronics and Research Laboratory, Defence Research and Development Organization, Hyderabad, India; Telecommunications Division, Electrical Engineering Department, Eindhoven University of Technology, Eindhoven, The Netherlands; and Wave Propagation Laboratories, National Oceanic and Atmospheric Administration, Boulder, CO. He has more than 30 years of experience in the areas of GPS, radio-wave propagation, and mobile communication. Thirteen students have obtained Ph.D under his guidance and is currently guiding several Ph.D students in these areas. He is currently the Director of the Research and Training Unit for Navigational Electronics (NERTU), Osmania University, Hyderabad. He has more than 200 papers to his credit. E-mail: [email protected]