Generating Observable-Specific Signal Biases to Reconcile BDS B1/B2 and B1/B3 Phase Bias Products for All-Frequency PPP Ambiguity Resolution

Qiyuan Zhang, Qiang Wen, Jiang Guo

Peer Reviewed

Abstract:	BDS-2 (BeiDou System-2) has been officially operational since 2012 by emitting B1/B2/B3 triple-frequency signals over the Asia-Pacific region. Initially, the International GNSS Service (IGS) chose B1I/B2I signals to routinely estimate satellite clock and phase bias products to enable undifferenced ambiguity resolution in precise point positioning (PPP-AR). However, the successor BDS-3 negates the B2I signal, which compels the IGS to switch to the B1I/B3I signals to compute both BDS-2/3 satellite products in a self-consistent manner. The aftermath is awkwardly the backward incompatibility with respect to the legacy BDS-2 B1I/B2I products. Reprocessing the archived BDS-2 data for B1I/B3I compatible products would be a viable solution, but tend to dump the previous IGS efforts of supporting BDS-2 PPP-AR. In this study, we propose to expand the BDS-2 B1I/B2I products to the B3I signals in the form of observable-specific signal biases (OSBs), rather than recompute the B1I/B3I products. Specifically, the legacy B1I/B2I satellite clocks are preserved without being re-estimated using the B1I/B3I signals; each signal has its individual OSB where the B1I/B2I OSBs are inherited from the legacy bias products whereas the B3I OSB is their extension to aim at compatibility with the B1I/B3I biases in BDS-3. As a result, the legacy BDS-2 satellite clock and phase bias products can be fully reused over the entire span of the BDS-2 operation in a consistent manner with the succeeding BDS-2/3 products. We carried out BDS-2 IGSO (Inclined Geosynchronous Satellite Orbiters) based kinematic PPP-AR using the B1I/B3I signals in a network of 20 stations spanning days 217 to 223 in 2019 across the Asia-Pacific region. On account of the time-variable phase biases over the B3I signal, we estimated piece-wise constant B3I OSBs every 15 minutes. The results show that, while our B1I/B2I OSBs can still ensure unimpaired conventional B1I/B2I PPP-AR, the B1I/B3I OSBs along with the legacy B1I/B2I satellite clocks can lead to almost the same ambiguity fixing rates and positioning precisions as those based on the dedicated B1I/B3I clock/phase bias products. In particular, their ambiguity fixing rates differ by no more than 1% on average, while their positioning precisions differ by 1.4, 0.7 and 0.1 mm in the east, north and up directions, respectively, both demonstrating the validity of expanding the legacy BDS2 B1I/B2I products to the B3I signals in the form of OSBs while maintaining full compatibility and equivalent performance.
Published in:	Proceedings of the 35th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2022) September 19 - 23, 2022 Hyatt Regency Denver Denver, Colorado
Pages:	2751 - 2766
Cite this article:	Zhang, Qiyuan, Wen, Qiang, Guo, Jiang, "Generating Observable-Specific Signal Biases to Reconcile BDS B1/B2 and B1/B3 Phase Bias Products for All-Frequency PPP Ambiguity Resolution," Proceedings of the 35th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2022), Denver, Colorado, September 2022, pp. 2751-2766. https://doi.org/10.33012/2022.18518
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