Optimal Time-of-Arrival Estimation for Enhanced DME

Kuangmin Li and Wouter Pelgrum

Abstract:	Next Generation Air Transportation System (NextGen), a comprehensive modernization of US air traffic, heavily relies on high performance Positioning Navigation and Timing (PNT). Global Navigation Satellite Systems (GNSS), in combination with Space Based Augmentation Systems (SBAS) and Ground-Based Augmentation Systems (GBAS) are instrumental in the provision of the required PNT performance. To mitigate the vulnerability of GNSS to, for example, RFI interference, significant solar activities, or constellation failures, a backup PNT solution is needed. Such GNSS-independent backup is referred to as APNT, Alternative Positioning Navigation and Timing. This paper focuses on DME-DME (Distance Measuring Equipment) as an APNT candidate, and potential ranging performance enhancements that can be achieved with a modernized DME system. Traditionally, DME/N uses the half-amplitude method and DME/P the virtual zero crossing to estimate the Time of Arrival (TOA) of a pulse pair. This paper analyzes these methods, as well as other methods such as curve fitting, correlation, and IFFT spectral division in terms of noise performance and multipath mitigation. Comparisons are made against derived theoretical optimal performance. Next, a measurement system is presented that allows performance evaluation of a potential future enhanced DME system using current legacy transponder installations. Flight test results show the instrumentation performance and its applicability for further signal processing research and validation, as well as for detailed L-band propagation measurements.
Published in:	Proceedings of the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2011) September 20 - 23, 2011 Oregon Convention Center, Portland, Oregon Portland, OR
Pages:	3493 - 3502
Cite this article:	Li, Kuangmin, Pelgrum, Wouter, "Optimal Time-of-Arrival Estimation for Enhanced DME," Proceedings of the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2011), Portland, OR, September 2011, pp. 3493-3502.
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