Flight Testing of the D8PSK/TDMA Datalink Technology for the Ground-based Regional Augmentation System

William S. Ely, Graeme K. Crosby, Keith W. McPherson and Joy M. Stewart

Abstract:	Since 2000, Airservices Australia’s Global Navigation Satellite Systems (GNSS) Program Office (GNSSPO) has been working with the International Civil Aviation Organisation (ICAO) GNSS Panel (GNSSP) on producing Standards and Recommended Practices (SARPs) for an alternate wide area augmentation system based on a Very High Frequency (VHF) data link. This Ground-based Regional Augmentation System (GRAS) was proposed due the financial, legal and institutional issues which Australia had identified as limiting the applicability of the satellite based solutions being progressed by the USA and other large economic nations. Following approval by ICAO’s Air Navigation Commission in 1999, the Differential Eight Phase Shift Keying (D8PSK)/Time Division Multiple Access (TDMA) data link technology, already accepted by ICAO for Ground Based Augmentation Systems (GBAS), was accepted as the basis for the GRAS data link. Airservices Australia has operated a test-bed network using six ground reference stations and two D8PSK/TDMA VHF transmitter sites for the past two years. This network has proven the viability of using a single VHF frequency to implement a GRAS over a large area such as Australia, using the TDMA properties of the technology to separate the signals from the various VHF transmitter sites. Flight tests conducted over the past two years have shown the viability of GRAS providing navigation services to Approach with Vertical Guidance Level 1 (APV I) and potentially Level 2 (APV II) parameters as defined by ICAO GNSS SARPs. The system has demonstrated the capability to support variable geometry approach paths such as curved final approach paths, different glidepath angles and variable touchdown points. This paper provides the results of flight tests conducted in the first half of 2002 which support the use of the D8PSK/TDMA data link, and the concept of using a single VHF frequency to implement a GRAS. These results will be used by the GNSSP to support validation of the GRAS SARPs, due for completion in 2003.
Published in:	Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002) September 24 - 27, 2002 Oregon Convention Center Portland, OR
Pages:	1038 - 1046
Cite this article:	Ely, William S., Crosby, Graeme K., McPherson, Keith W., Stewart, Joy M., "Flight Testing of the D8PSK/TDMA Datalink Technology for the Ground-based Regional Augmentation System," Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002), Portland, OR, September 2002, pp. 1038-1046.
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