Tracking and Multipath Performance Assessments of BOC Signals Using a Bit-Level Signal Processing Simulator

L. Ries, F. Legrand, L. Lestarquit, W. Vigneau, J-L. Issler

Abstract:	The Binary Offset Carrier or BOC modulation, defined as the product between the spreading code and a squared sub-carrier, is currently seen as a serious candidate for many future RadioNavigation signals, including several GALILEO signals as well as the GPS M-Code. This modulation has been studied last year by M3Systems under CNES contract, leading among others to the development of a bit-level signal-processing simulator (software receiver). During this study, BOC modulation has been analyzed as a particular case of the offset carrier modulation, and many variants of the BOC modulation have been identified and investigated. These include the LOC (or Double-PSK, i.e. with a sine sub-carrier) and their alternative versions, where signals on the upper and lower bands of the spectrum carry different codes and/or messages, thus offering service diversity on a same carrier. Assessments of the effect of the code and sub-carrier phase offset and the duty-cycle of the squared sub-carrier have been performed using the simulator. They have shown, for example, that a particular phasing of the sub-carrier leads to reduce the width of the main correlation peak of a BOC signal, enhancing the tracking performances and the multipath mitigation. The purpose of this paper is to address simulation results in term of tracking performances and multipath robustness in the case of the offset carrier modulation options previously presented. These results are then discussed with regards to the associated implementation complexity in both the satellite payload and the receiver chipset. The first part of the paper recalls the formal expressions of the different possible offset carrier modulations and their main properties (correlation function and spectrum). An opportunity to modulate four different services on a same BOC signal featuring a constant envelope, so called ALTBOC, is presented and its tracking capabilities demonstrated. The second part is dedicated to the tracking aspect: adapted tracking architectures are proposed and discussed in term of complexity. Simulation results are presented in the third part and conclusions about the compromise between the complexity of the system architecture (payload and receiver) and the tracking performances (in terms of robustness against thermal noise and multipath) are proposed.
Published in:	Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003) September 9 - 12, 2003 Oregon Convention Center Portland, OR
Pages:	1996 - 2010
Cite this article:	Ries, L., Legrand, F., Lestarquit, L., Vigneau, W., Issler, J-L., "Tracking and Multipath Performance Assessments of BOC Signals Using a Bit-Level Signal Processing Simulator," Proceedings of the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS/GNSS 2003), Portland, OR, September 2003, pp. 1996-2010.
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