Adaptive Replica Code Synthesis for Interference Suppression in GNSS Receivers

Chun Yang and Jade Morton

Abstract:	The removal of strong components from a signal allows the acquisition of weaker components of the signal, otherwise masked by the strong components. This masking effect is due to the small cross-correlation between the strong and weak signal components (e.g., GPS spreading codes), which appears as interference, also known as multiple access noise. In this paper, we investigate various interference suppression techniques. Interference suppression is typically done by subtracting already acquired strong components from the received signals (an additive operation) prior to acquiring weak components. This successive interference suppression approach in the signal domain is shown to be equivalent to that in the correlation domain. Instead of individually or successively, all acquired strong components can be removed at once by finding an equivalent strong signal in the interference subspace via either an orthogonal or oblique projection. Furthermore, removing strong components can be formulated as finding an equivalent code replica that is not only close to the desired weak component but also orthogonal to the strong components (a multiplicative operation). The design of such an equivalent code replica, adaptive to the acquired strong components, can be cast as a constrained optimization problem. Various formulations of constrained optimization are presented and their solutions are derived and analyzed in the paper.
Published in:	Proceedings of the 2009 International Technical Meeting of The Institute of Navigation January 26 - 28, 2009 Disney's Paradise Pier Hotel Anaheim, CA
Pages:	131 - 138
Cite this article:	Yang, Chun, Morton, Jade, "Adaptive Replica Code Synthesis for Interference Suppression in GNSS Receivers," Proceedings of the 2009 International Technical Meeting of The Institute of Navigation, Anaheim, CA, January 2009, pp. 131-138.
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