Performances of Multicorrelator-based Maximum Likelihood Discriminator

G. Carrie, D. Kubrak, M. Monnerat

Abstract:	Multipaths are still one of the major error sources in Global Navigation Satellite Systems operating in challenging environments such as urban areas. This paper presents how a multicorrelator-based maximum likelihood discriminator may improve the multipath mitigation performances. The general principle of the algorithm consists in computing a likelihood metric between the computed sampled correlation function and a parametric reference correlation function. The likelihood metric relies on a model of the noise autocorrelation function after the correlation step with the local code replica. The set of parameters (code phase error, carrier phase error and carrier frequency error) that enable to maximize the likelihood metric constitute the delay and phase or frequency discriminator outputs. The theoretical performances of the proposed maximum likelihood discriminator have been derived in a white noise context as a function of the signal to noise ratio, the available bandwidth and the number of correlators for several GNSS waveforms. These performances were confirmed by numerical simulations. The theoretical performances of the solution were also evaluated when multipath are present. A specific version of the algorithm has been designed to detect and count multipath and to estimate their parameters. A software simulator based on an urban physical-statistical channel model has been used to evaluate the proposed solution in presence of multipath and shadowing events. The multicorrelator-based maximum likelihood discriminator outperformed conventional discriminators both in terms of accuracy and availability of the navigation solution.
Published in:	Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014) September 8 - 12, 2014 Tampa Convention Center Tampa, Florida
Pages:	2720 - 2727
Cite this article:	Carrie, G., Kubrak, D., Monnerat, M., "Performances of Multicorrelator-based Maximum Likelihood Discriminator," Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014), Tampa, Florida, September 2014, pp. 2720-2727.
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