The Optimal Dual Estimate Solution for Robust Tracking of Binary Offset Carrier (BOC) Modulation

M.S. Hodgart, P.D. Blunt and M. Unwin

Abstract:	Binary Offset Carrier (BOC) is a very different way of modulating navigation signals which has been adopted for the next generation GNSS. Unfortunately in a conventional receiver, copying the general principles of PSK demodulation (as used in current GPS), a multipeaked correlation function is generated which can lead to problems of false lock or ‘false node tracking’ on a secondary rather than a primary peak. The problem is well-known. Published remedies to the problem have not been entirely successful or optimal (in sense of least square error). A radically different approach described here generalises the correlation into two dimensions within what we name as a dual estimating receiver. Two complementary estimates of the time-delay of the input signal are generated: a lower accuracy but unambiguous estimate responding purely to the code modulation; and a higher accuracy but ambiguous estimate responding purely to the sub-carrier modulation. The two estimates are then combined in a simple arithmetic operation to a single joint estimate which fully exploits the capabilities of BOC. Implementation is by a triple loop rather than the double loop of conventional receivers.
Published in:	Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007) September 25 - 28, 2007 Fort Worth Convention Center Fort Worth, TX
Pages:	1017 - 1027
Cite this article:	Hodgart, M.S., Blunt, P.D., Unwin, M., "The Optimal Dual Estimate Solution for Robust Tracking of Binary Offset Carrier (BOC) Modulation," Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2007), Fort Worth, TX, September 2007, pp. 1017-1027.
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