Evaluation of the New WAAS L5 Signal

Hyunho Rho, Richard B. Langley

Abstract:	The current GPS constellation is being modernized to enhance the performance of the legacy GPS signals. As a part of the GPS modernization efforts, a new third civil signal, L5 at 1176.45 MHz will join the current civil signal on L1 at 1575.42 MHz and the second civil signal on L2 at 1227.60 MHz. Since the Wide Area Augmentation System (WAAS) is compatible with the GPS modernization, both WAAS geostationary Earth orbiting satellites (GEOs), Galaxy XV (PRN135) and Anik F1R (PRN138) contain an L1 and L5 GPS payload and currently broadcast both signals on the air. The main objective of the research described in this paper is the evaluation of the new WAAS L5 signal. In the work reported in this paper, the overall quality of the new WAAS L5 signal was investigated by comparing selected signal quality indices, such as the carrier power to noise density ratio (C/N0) and multipath plus noise level, between the L1 and L5 signals. Since WAAS GEO signals are generated by the ground control segment and uplinked to GEOs to broadcast the signals on the air (a so-called “bent-pipe” approach), the ionospheric delays as well as differential code bias (DCB) should be estimated and compensated for in both the uplink and downlink signals. The behavior of the DCB for PRN138 has been further analyzed in this research. This paper presents the evaluated results for the new WAAS L5 signal quality and the identified WAAS GEO satellite DCBs as well as some discussions about the possible benefit of the WAAS GEO ranging measurements in the positioning domain.
Published in:	Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008) September 16 - 19, 2008 Savannah International Convention Center Savannah, GA
Pages:	1667 - 1678
Cite this article:	Rho, Hyunho, Langley, Richard B., "Evaluation of the New WAAS L5 Signal," Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008), Savannah, GA, September 2008, pp. 1667-1678.
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