Optimal Pulsing Schemes for Galileo Pseudolite Signals

Tin Lian Abt, Francis Soualle and Sven Martin

Abstract:	Galileo, the European Satellite Navigation System, is currently under development. Even before first satellites of the constellation will be launched, Galileo signals will be provided through ground based Navigation Signal Generators for the investigation of signal performance and characteristics. Currently various projects are ongoing to develop these Galileo pseudolites (pseudo satellites). Since pseudolites are part of the Galileo system architecture namely as “Local Elements” it is expected that they will be used together with GNSS for position determination. The main characteristic of pseudolite navigation is the relatively small distance between the signal source and the receiver compared to the GNSS satellites. This distance causes the so-called “Near-Far-Problem”. Different attempts have been made in the past to overcome the near-far problem. A possible solution is pulsing of the pseudolite transmitter signal which has been proposed by many authors and the success of pulsing has also been demonstrated. Basically these studies have been focused on GPS in the past and the proposed pulsing schemes are optimised for GPS signals (RTCM, RTCA). Due to major differences in the signal structure between GPS and Galileo these pulsing schemes cannot directly be adopted. Thus new pulsing schemes and patterns have to be found and investigated. This paper summarises and assesses the existing GPS pulse patterns and pulsing techniques. The parameters which characterise a pulsing scheme are discussed and implemented. Simulations based on the Galileo signal structure (codes, chipping rates, cross correlation properties) have been performed and the results will be presented. These simulations form the basis for the proposal of a new optimised pulsing scheme for Galileo pseudolites w.r.t. pulse length, duty cycles and pulse patterns.
Published in:	Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005) September 13 - 16, 2005 Long Beach Convention Center Long Beach, CA
Pages:	926 - 934
Cite this article:	Abt, Tin Lian, Soualle, Francis, Martin, Sven, "Optimal Pulsing Schemes for Galileo Pseudolite Signals," Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005), Long Beach, CA, September 2005, pp. 926-934.
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