Development of a Wideband Airport Pseudolite for GPS Augmentation

Chris G. Bartone and Sai Kiran

Abstract:	This paper focuses on a wideband (WB) airport pseudolite (APL) for possible implementation as part of the Local Area Augmented System (LAAS). The LAAS is a differential GPS (DGPS) precision approach system that is based on a carrier-smoothed code architecture. APLs are being developed in order to increase system availability at LAAS Category II/III installations. The primary error source for the APL link at the LAAS Ground Facility (LGF) is the ground-to-ground multipath. Characterization of the APL link performance in the presence of ground-to-ground multipath is the primary emphasis of this paper. Using a Multipath Limiting Antenna (MLA) for APL transmission, and two MLAs and two High Zenith Antennas (HZAs) for GPS and APL signal reception, Double Difference (DD) Error and Bias-Value (B-value) analyses are used to assess the performance of the ground APL link. GPS DD and B-values are the parameters used for baseline comparison. Cases involving APL transmission of both the C/A and WB codes of PRN 34 using two separate pulsing schemes, a Modified RTCA Format and a 1/11 th Pulsing Format, are assessed and presented. The tests were conducted without performing radio frequency (RF) gain control and blanking. On using the HZAs for reception of the Modified RTCA Pulsing Format, the WBAPL DD and B-values were seen to be 1.33 meters and 0.73 meters, respectively. Better performance was attained when the MLAs were used for reception. In this case the WBAPL DD and B-values (average of the absolute values) were seen to be -0.54 meters and 0.32 meters, respectively, for the Modified RTCA Pulsing Format. On using the HZAs for reception of the 1/11 th Pulsing Format, the WBAPL DD and B-values were found to be 1.19 meters and 0.65 meters, respectively. Better performance was attained when the MLAs were used for reception of this pulsing format as well, in which case WBAPL DD and B-values of-0.15 meters and 0.16 meters, respectively, were obtained. GPS Performance Parameters (DD and B-values) were monitored, and they showed no adverse electromagnetic interference (EMI). It was noted that when the 1/11 th Pulsing Format was used, the GPS Performance Parameters showed a very slight increase in residual error (DD and B-value variance) over the modified RTCA Pulsing Format. However, the WBAPL Performance Parameters (DD and B-values) were seen to be slightly better with the 1/11 th Pulsing Format.
Published in:	Proceedings of the 2000 National Technical Meeting of The Institute of Navigation January 26 - 28, 2000 Pacific Hotel Disneyland Anaheim, CA
Pages:	50 - 57
Cite this article:	Bartone, Chris G., Kiran, Sai, "Development of a Wideband Airport Pseudolite for GPS Augmentation," Proceedings of the 2000 National Technical Meeting of The Institute of Navigation, Anaheim, CA, January 2000, pp. 50-57.
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