Article Figures & Data
Figures
- FIGURE 1
Schematic representation of BeiDou-2 and BDS-3 signal spectra in the lower and upper L-band; blue and red colors indicate open service and restricted signals, respectively. In-phase (I) and quadrature-phase (Q) components are shown on orthogonal planes. Next to its name, the modulation scheme is indicated for each signal (BPSK: binary phase shift keying; BOC: binary offset carrier; QMBOC: quadrature multiplexed binary offset carrier; ACE-BOC asymmetric constant envelope binary offset carrier). Numbers in brackets denote the chipping rates of the ranging codes and sub-carriers in multiples of 1.023 MHz.
- FIGURE 2
Mean values of broadcast DCBs provided in the BeiDou navigation messages over the year 2021
- FIGURE 3
Temporal evolution of TGD1 values transmitted in 2021 by BDS-2 and BDS-3 satellites (colors from blue to red refer to individual spacecraft in the order of ascending SVN)
- FIGURE 4
Box-whisker plots showing the median (colored lines), inter-quartile range (IQR; shaded boxes), and 1.5⋅IQR whiskers of standard deviations of individual satellite DCBs in the CAS and DLR products for the BDS-2 and BDS-3 constellation; outliers exceeding the 1.5⋅IQR limits are marked by open circles.
- FIGURE 5
Standard deviation of DCB differences between DLR and CAS products, as well as broadcast TGDs and CAS DCBs
- FIGURE 6
Differences of broadcast TGD1 and CAS C2I-C6I DCBs for BDS-3 MEO satellites; colors from blue to red denote individual satellites in ascending SVN order.
- FIGURE 7
Scatter plot of TGD1 – DCBC2I-C6I differences illustrating the receiver type dependence of B1I-B3I group delays (bold black plus signs indicate the mean value of the TGD-DCB difference for BDS-2 and BDS-3 satellites after zero-mean alignment of the constellation-wide differences; s denotes the slope of a trendline relating data for each receiver pair)
- FIGURE 8
Scatter plot of TGDB1Cp – DCBC1P-C6I and TGDB1Cp – TGDB2ap – DCBC1P-C5P differences illustrating the receiver type dependence of B1C-B3I and B1C-B2a group delays (in the case of Trimble and Javad receivers, pilot-only DCBs were substituted by DCBs from pilot+data tracking; s denotes the slope of a trendline relating data for each receiver pair)
- FIGURE 9
Satellite-specific clock biases
of broadcast ephemerides relative to precise ephemerides for different user signals s and satellites i
Tables
Signal Band f0 [MHz] RINEX Nav. Msg. Satellites B1C(d+p) B1 1575.420 C1D/P/X CNAV-1 BDS-3 B1I B1-2 1561.098 C2I D1/D2 BDS-2/3S/3 B3I B3 1268.520 C6I D1/D2 BDS-2/3S/3 B2I B2b 1207.140 C7I D1/D2 BDS-2 B2b-I/[Q] B2b 1207.140 C7D/P/Z CNAV-3 BDS-3 B2a(d+p) B2a 1176.450 C5D/P/X CNAV-2 BDS-3 [B2ab] B2ab 1191.795 C8D/P/X – BDS-3 Note: Square brackets denote selected signals that are transmitted and can be tracked by various receivers but are not formally described as part of an official signal specification. Next to the center frequency f0, the corresponding RINEX observation codes and the navigation messages transmitted on the respective signals are provided.
Navigation Message Signal Group Delay Parameter RINEX Equivalent D1/D2 B1I, B2I, B3I TGD1 C2I-C6I TGD2 C7I-C6I CNAV-1 B1C TGDB1Cp C1P-C6I TGDB2ap C5P-C6I ISCB1cd C1D-C1P CNAV-2 B2a TGDB1Cp C1P-C6I TGDB2ap C5P-C6I ISCB2ad C5D-C5P CNAV-3 B2b-I TGDB2bI C7D-C6I - TABLE 3
Number of Stations Contributing to CAS and DLR DCB Products Near the Beginning and Ending of 2021
Signal CAS DLR Begin End Begin End C2I 190 205 110 120 C6I 140 180 95 110 C7I 190 205 110 120 C1P 40 90 30 50 C1X 25 50 25 35 C5P 40 90 30 50 C5X 30 90 30 35 C7D 10 60 C7Z 20 35 20 20 C8X 20 35 15 15 Set Receivers Number 1 Javad TRE_3 30 2 Leica GR10/25/30/50 15 3 Septentrio AsterRx-4, PolaRx-4TR/-5/-5TR 30 4 Trimble NetR9, Alloy 20–45 Note: The number of contributing stations may differ for legacy and modernized signals.
- TABLE 5
Signal-Dependent Group Delay Corrections of Satellite Clock Offsets in Broadcast Ephemerides (bce) and Precise Reference Ephemerides (ref) for SISRE Monitoring of Selected Single- and Dual-Frequency Navigation Services
Message User signal(s) Broadcast Reference D1 B1I B3I B1I, B3I CNAV-1 B1C B3I B1C, B3I B2a B1C, B2a Note: fb denotes the frequency for the frequency band b (cf. Table 1).
Message Signals SISREorb T SISRE T0 Tb D1 B1I 0.12 0.38 0.40 0.25 0.28 B3I 0.12 0.44 0.45 0.25 0.35 B1I, B3I 0.12 0.60 0.62 0.25 0.56 CNAV-1 B1C 0.11 0.42 0.43 0.25 0.33 B3I 0.11 0.44 0.45 0.25 0.35 B1C, B3I 0.11 0.53 0.54 0.25 0.48 B2a 0.11 0.41 0.43 0.25 0.32 B1C, B2a 0.11 0.45 0.46 0.25 0.38 D1+CNAV-2 B1I, B2a 0.11 0.42 0.43 0.25 0.34 Note: All values in m.
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