Development of a Carrier and C/A-Code Based Pseudolite System

Martin Weiser

Abstract:	Pseudolites play an important role in today’s concepts to achieve ICAO Cat. III performances for local area system designs. Besides airborne applications, they may be a generally interesting local augmentation for satellite navigation systems in adverse environments. To demonstrate the suitability of Pseudolites for all applications in the mass market of air-, road- and railway-traffic as well as for specific solutions in the area of logistics a Pseudolite system was developed which meets the following requirements: The Pseudolite transmitter, a slightly modified single channel GPS simulator card, is low in price compared to existing systems and transmits a signal which is widely compatible to GPS. This in turn leads to a standard, low-cost receiver architecture which can be derived from existing GPS receiver designs with minor software modifications with respect to data decoding and navigation. The modifications are necessary since the position of the Pseudolite on earth cannot be described as a set of parameters of a Kepler ellipse which is used to broadcast the satellites’ position in the orbit. Since it is the objective of Pseudolites to work even under adverse conditions the message frame length and the message size was shortened to allow a fast acquisition and reacquisition of the signal. First flight- and driving-tests demonstrated a system accuracy which is similar to differential GPS. For most applications the C/A-code can be used to determine the range between the Pseudolite and the user. Some first results also indicate the general suitability of Pseudolites for indoor navigation. For this particular application a code based ranging is not possible due to the difficult environment generating reflections which lead to large multipath errors. In this case the carrier phase is used to achieve an accurate positioning.
Published in:	Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998) September 15 - 18, 1998 Nashville, TN
Pages:	1465 - 1475
Cite this article:	Weiser, Martin, "Development of a Carrier and C/A-Code Based Pseudolite System," Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998), Nashville, TN, September 1998, pp. 1465-1475.
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