Towards Multi-Constellation Collective Detection for Weak Signals: A Comparative Experimental Analysis

Joon Wayn Cheong

Abstract:	Collective detection is a GNSS receiver signal processing technique that combines the correlator output of all satellite channels and projects them onto the position-clock space to enhance the overall signal detection probability, given that a priori knowledge of satellite ephemeris, and approximate user location is known to the receiver. This is an enhancement to pre-existing GNSS signal processing techniques, where the gains acquired from Collective Detection can be leveraged on longer coherent/non-coherent integration periods, making it viable even at 20dB-Hz C/No [1, 2] The aim of this paper is to evaluate the performance of various Collective Detection methods in comparison to the conventional method. The performance evaluations are brought closer to reality by using digitized live signals for processing. An optimization algorithm, namely SAGE is introduced into the comparison due to its potential to reduce the computational requirement by at least an order of magnitude. Collective Detection is shown to be 3dB more sensitive than conventional methods (in 90% Pdsense) via comparing the same strong satellite experimentally. In the case of weaker satellite signals, Collective Detection is able to exploit strong signals so that weak signals are able to be detected at the same Pd as the strong signal although its C/No is much weaker. Combined GPS + Locata acquisition via collective detection is implemented to demonstrate the viability of multi-constellation Collective Detection. In this example Locata is used to represent another satellite constellation (e.g. GLONASS, GALILEO etc.). As an example, The C/No requirement to achieve 100m accuracy is lowered by a 6dB margin by just a simple addition of one pseudolite transmitter into Collective Detection. On top of achieving higher sensitivity and higher detection rates for weak signals, Collective Detection is also shown to be able estimate the receiver position prior to entering tracking loops. This is useful to provide a rapid position solution or a better initialization to the position-domain Integrated Kalman Filter, when applicable.
Published in:	Proceedings of the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2011) September 20 - 23, 2011 Oregon Convention Center, Portland, Oregon Portland, OR
Pages:	3709 - 3719
Cite this article:	Cheong, Joon Wayn, "Towards Multi-Constellation Collective Detection for Weak Signals: A Comparative Experimental Analysis," Proceedings of the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2011), Portland, OR, September 2011, pp. 3709-3719.
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