Architecture of Software of TFAG50 Low-Cost Low Power GPS/GLONASS Receiver

Alexander Fridman and Serguei Semenov

Abstract:	In many real-life situations, for example in urban environment, GPS signals are often masked by obstructions, resulting in degraded geometry and accuracy, or even unavailability. The added availability of GLONASS satellites would not only increase the number of visible satellites, which is the case at any location, but would provide a much better integrity capability. Taiwan Falcon Aerospace Corporation has recently developed a low-cost low-power dual GPS/GLONASS receiver, TFAG50, which is aimed to enhance positioning capability owing to GLONASS while keeping in lowprice class as well as low-power one. Each of 16 receiver channels can be tuned to a GPS, GLONASS or WAAS signal, and this means that GLONASS enhancement is achieved with no degradation as compared to a GPS-only 16-channel receiver. ADSP-2189M is used as a Navigation CPU because of its low cost and a plenty of on-chip memory which allowed to eliminate any need of high-speed on-board RAM. Owing to that, both power and cost savings became feasible. Overlay memory architecture of the ADSP-2189M does not allow more than 8 K instructions for each overlay executable module. Because full receiver software significantly exceeds 8 K, a special "Operating Shell" has been developed. This paper describes its structure and functionality, as well as general approach to integration of different program and data modules (which are stored in different overlay pages of on-chip memory as well as flash memory and low-speed byte-width SRAM) into a real-time computing system. Main features of Channel software, Search and Detection System, Track Software, Navigation Solution Software etc. will be described. Experimental results with live GPS and GLONASS signals will be presented as well as that of road tests in urban environment. They will demonstrate high accuracy and fast reacquisition times of TFAG50 GPS/GLONASS receiver.
Published in:	Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001) September 11 - 14, 2001 Salt Palace Convention Center Salt Lake City, UT
Pages:	768 - 777
Cite this article:	Fridman, Alexander, Semenov, Serguei, "Architecture of Software of TFAG50 Low-Cost Low Power GPS/GLONASS Receiver," Proceedings of the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2001), Salt Lake City, UT, September 2001, pp. 768-777.
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