Testing of GPS Augmented with Pseudolites for Precision Approach Applications

Bryant Elrod, Kevin Barltrop, A. J. Van Dierendonck

Abstract:	In theory, pseudolites (PLs) can be configured to transmit compatible GPS-like signals for augmenting the satellite constellation, similar to signals designed for the Wide Area Augmentation System (WAAS), providing integrity warning information and enhancing navigation accuracy through improved geometry and differential GPS (DGPS) support (code and carrier). While many technical issues are often raised concerning their use (e.g. the near/far signal interference problem, aircraft antemm requirements, etc.), PLs are now being evaluated for a potential role in enhancing GPS to meet precision approach requirements for accuracy, integrity and availability in the U.S. National Airspace System and elsewhere. Research is in progress to vigorously assess the reality of issues relating to PL usage and to investigate the effectiveness of proposed methods to solving or mitigating them. This paper discusses a PL signal structure which is designed to operate within the GPS Ll frequency band increase the message data rate to 50N bps (up to N=20) and significantly mitigate the near/far issue. The results of using realistic GPS and PL signal generators for testing the performance of several commercial receivers with a PL signal present are given. Initial flight test results are presented for the PL data link performance at 250 bps during terminal area operations using a GSV- 1003 (DGPS/WAAS/PL capable) receiver. Plans for subsequent full scale testing to assess navigation performance and implementation issues with code and/or carrier-based DGPS/PL operations are also outlined.
Published in:	Proceedings of the 7th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1994) September 20 - 23, 1994 Salt Palace Convention Center Salt Lake City, UT
Pages:	1269 - 1278
Cite this article:	Elrod, Bryant, Barltrop, Kevin, Van Dierendonck, A. J., "Testing of GPS Augmented with Pseudolites for Precision Approach Applications," Proceedings of the 7th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1994), Salt Lake City, UT, September 1994, pp. 1269-1278.
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