Real-time Multipath Monitoring and Characterization with a Variable Spacing Correlator on a FPGA-Based Software GNSS Receiver

Jean-Christophe Guay, Bruno Sauriol, Marc-Antoine Fortin

Abstract:	In the past few years, the complexity of Field Programmable Gate Array (FPGA) has considerably increased. Its flexibility and high throughput have allowed new applications to arise, taking advantage of the technology. Recent research projects on software GNSS receivers have tested different possibilities of this technology. In the case of this paper, a new approach of multipath monitoring and characterization with a variable spacing correlator is introduced. The size of this new correlator allows an easily implementation in each channel. First, the paper presents multipath basics and some example of multipath scenarios to which the multipath monitor will be submitted. Then, the limits of the actual multipath tests and metrics used to monitor and characterize a multipath signal will be presented. To introduce the variable spacing correlator, the Software GNSS Receiver (SGR) developed at ETS is summarized. Then, the paper describes a way to use this powerful tool in real-time for multipath monitoring and characterization. Three tests are proposed: the Normalization Coefficient Ratio (NCR), the Symmetric Difference Count (SDC) and the Theoretical Differential Sum (TDS). Finally, these tests results are presented and discussed. In conclusion, the variable spacing correlator can be used to detect a multipath as low as 27.5 dB below the direct signal. It can also be used to characterize short delay multipath. Moreover, the tools could be used to determine the amplitude of the multipath delay in real-time.
Published in:	Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008) September 16 - 19, 2008 Savannah International Convention Center Savannah, GA
Pages:	2332 - 2342
Cite this article:	Guay, Jean-Christophe, Sauriol, Bruno, Fortin, Marc-Antoine, "Real-time Multipath Monitoring and Characterization with a Variable Spacing Correlator on a FPGA-Based Software GNSS Receiver," Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008), Savannah, GA, September 2008, pp. 2332-2342.
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