Signal Multiplex Techniques in Satellite Channel Availability Possible Applications to Galileo

A.R. Pratt and J.I.R. Owen

Abstract:	There is a requirement with all satellite navigation systems to provide several services (more than 2) in each transmission band. GPS signals in L1 will be multiplexed at least 4 ways to provide CA code, P(Y) code, M-code and LIC signals. Similarly, Galileo will have its transmission on L1 multiplexed 3 ways to provide PRS, L1-OS data and L1-OS pilot signals, each with double sided spectra. Galileo signals in E5 are multiplexed to sustain 4 signals using an approach known as Alt-BOC which provides single sided spectra having isolation between pairs of signals. Mostly, multiplexing aims to provide a multiplicity if signals which may coexist on the same carrier without mutual interference. The relationship between the 2 published techniques, CASM and Interplex, is explained. Alternative methods of multiplexing may use separate antenna and amplifier chains which allow signal combination in the far field of the satellite antenna system. This poses difficulties for the spacecraft payload due to the extra components and for the antenna design, poor power efficiency, cost and weight. The paper focuses on characteristics of the current multiplexing techniques and provides analysis of the present Galileo additive methodology. This reveals characteristics which lead to a number of optional receiver techniques. The receiver options are explored in system characteristic terms. It is shown how the multiplexing technique can be exploited to improve the susceptibility to external interference compared with the use of the same transmitted power but without signal multiplexing.
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:	2448 - 2460
Cite this article:	Pratt, A.R., Owen, J.I.R., "Signal Multiplex Techniques in Satellite Channel Availability Possible Applications to Galileo," 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. 2448-2460.
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