Applying "BOC-Gated-PRN" to Multiplexed Binary Offset Carrier (MBOC) Signals

J. Wu

Abstract:	The Multiplexed Binary Offset Carrier (MBOC (6, 1)) signal is adopted to provide agreed [1], [2] common power spectral density for Galileo E1 Open Service (OS) and GPSIII L1C signals. In MBOC, a small amount of energy from a BOC signal with higher subcarrier frequency (i.e. BOC (6, 1)) is linearly added to the portions belong to the previous common baseline signal (i.e. BOC (1, 1)) to improve the potential receiver tracking performance, particularly with respect to noise and multipath. Following that agreement, the MBOC (6, 1) is generated for Galileo as Composite BOC (CBOC) and Time-multiplexed BOC (TMBOC) for GPSIII L1C. However, it is realized that the conventional receiver implementation may be not the optimum solution for this modernized Global Navigation Satellite System (GNSS) signal in some heavy interference environments because of two limitations: 1) the existence of the common tracking problem known as “false lock” or ambiguous tracking of the BOC signal, and 2) when tracking MBOC with a wider reference waveform gating window, the receiver may suffer from degraded multipath mitigation and reliability. The BOC-Gated-PRN (denoted as BOCGPRN) Delay Lock Loop (DLL) discriminator is a solution that is designed to track the BOC (1, 1) signal by aligning the incoming BOC signal with the locally generated tailored pseudorandom number (PRN) code instead of the subcarrier modulated BOC signal. The resulting discriminator is unambiguous with flexibly scaled shaping determined by the tailored gate width. In this paper, we investigate the tracking performance of the BOC-GRPN applied to the MBOC signal, including both CBOC and TBOC modulation schemes. Its multipath mitigation is analysed in particular and compared to the conventional tracking algorithm. The optimized BOCGPRN is identified for the MBOC associated with different modulation schemes. The non-coherent Costas Lock Loop receiver architecture is implemented to evaluate the noise performance and tracking reliability. Applying the BOC-GPRN DLL discriminator to MBOC, several of its advantages are retained: unambiguous tracking, overall improved multipath mitigation with flexible choice of gate width, low architectural complexity, and good tracking reliability and noise performance, with the cost of narrower hold-in range. In general, the BOC-GPRN is one of those solutions that can be used to explore the overall potential of MBOC even for low cost receivers with marginally sufficient sampling rate.
Published in:	Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009) September 22 - 25, 2009 Savannah International Convention Center Savannah, GA
Pages:	3209 - 3218
Cite this article:	Wu, J., "Applying "BOC-Gated-PRN" to Multiplexed Binary Offset Carrier (MBOC) Signals," Proceedings of the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2009), Savannah, GA, September 2009, pp. 3209-3218.
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