High‐precision unambiguous tracking technique for BDS B1 wideband composite signal

Abstract

In the BeiDou Navigation Satellite System (BDS) B1 band, a single‐sideband complex binary offset carrier (SCBOC) modulation is employed to combine the legacy and the modernized B1 signals into an asymmetric‐wideband composite signal for the backward compatibility. However, SCBOC modulation has only been regarded as a means to achieve the co‐existance between B1I and B1C signals, whose high‐precision ranging potential is not fully understood or exploited. In this paper, a new pathway for BDS B1 receivers to further enhance their ranging precision is established for the first time, by proposing an unambiguous cross‐assisted tracking (CAT) loop, which fully exploits the ranging performance of the SCBOC subcarrier and the inherent coherence between components in the composite signal. Simulation and experiment using live BDS‐3 signals show that compared to the traditional tracking processing for independent components, the CAT loop can significantly improve ranging performance precision, thus providing a high‐precision processing mode for the BDS B1 composite signal.

Reconstructing GNSS Meta-Signal Observations Using Sideband Measurements

“…In the DPE, the subcarrier is assimilated to a carrier component, which is tracked with a modified PLL. As previously discussed, DE/DPE processing can be applied to meta-signals as demonstrated by Gao et al (2020aGao et al ( , 2020b, Wang et al (2017), andZhang et al (2019).…”

“…A possible architecture for meta-signal processing (Gao et al, 2020a(Gao et al, , 2020b) is shown in Figure 3. In this case, the correlators obtained from the two sideband FIGURE 2 Schematic representation of standard GNSS tracking with a DLL/PLL architecture applied independently to the two sideband components components are coherently summed to obtain a single meta-signal correlator output.…”

“…These components will be multiplexed into one composite signal and can thus be considered a meta-signal. In this respect, research (Gao et al, 2020a(Gao et al, , 2020bWang et al, 2017;Zhang et al, 2019) has been performed to develop tracking algorithms that optimally exploit the benefits of the wideband B1 signal and solve the ambiguity problem. Wang et al (2017) extended the double estimator (DE)/double phase estimator (DPE) algorithm to avoid the ambiguity problem and demonstrated improved tracking performance for the B1 composite signal.…”

“…In Gao et al (2020aGao et al ( , 2020b, cross-aided tracking (CAT) is introduced. Additionally in this case, a dedicated loop, the subcarrier phase lock loop (SPLL), is used to track the subcarrier component and to avoid correlation secondary peaks.…”

“…After establishing the different relationships between meta-signals and sideband observations, we adopted the approach proposed by Hodgart and Blunt (2007) and used elsewhere (Gao et al, 2020a(Gao et al, , 2020bWang et al, 2017;Zhang et al, 2019) to compute the final high-accuracy pseudoranges. In this respect, we show that high-accuracy pseudoranges equivalent to those obtained through meta-signal processing can be found by combining carrier phases and pseudoranges from sideband components.…”