Session B5: Receiver Design, Signal Processing, and Antennas

Comprehensive Assessment of BDS-3 B1 and B2 Wideband Multiplexed Signal in Enhancing Ranging and Positioning Performance
Jiahe Chen, Yunhan Qi, Zheng Yao, Mingquan Lu, Department of Electronic Engineering, Tsinghua University; Beijing National Research Center for Information Science and Technology
Location: Beacon B

In recent years, to meet the increasing demands for high-precision and diversified positioning, navigation and timing (PNT) services, the BeiDou Global Navigation Satellite System (BDS-3) has implemented advanced signal structures and multiplexing technologies in multiple frequency bands. In the B1 band, BDS-3 not only retains the legacy BDS-2 B1I signal with central frequency at 1561.098 MHz, but also broadcasts a new modernized B1C signal with central frequency at 1575.42 MHz. To enhance broadcasting efficiency, BDS-3 employs a unique cross-frequency multiplexing technique. This technique combines B1I and B1C signals into a wideband multiplexed signal (WMS) using a complex-value subcarrier component with a frequency of 14.322 MHz, referred to as B1 WMS. Meanwhile, in the B2 band, BDS-3 broadcasts two quadrature phase shift keying (QPSK) modulated signals, B2a and B2b, the central frequencies of which are at 1176.45 MHz and 1207.14 MHz respectively. They are combined into B2 WMS using asymmetric constant envelope binary offset carrier (ACE-BOC) modulation with two complex-value subcarriers with frequencies of ±15.345 MHz.
To process BDS-3 signals, conventional receivers ignore the complex-value subcarrier components in B1 and B2 WMSs, receive and process each of the signal component independently, which can only obtain meter-level pseudorange measurements and meter-level single-point positioning results. It should be noted, however, that since the complex-value subcarrier components have much higher frequencies than the spreading codes, they have the potential for higher precision ranging and positioning.
Recent research has demonstrated high-precision tracking of BDS-3 WMSs through joint processing of upper and lower sideband signal components. However, these studies have primarily focused on thermal noise resistance analysis of B1 and B2 WMSs, lacking comprehensive evaluation of multipath mitigation performance. Moreover, existing studies are limited to single-frequency, short-term performance analysis in simplified scenarios, without considering dual-frequency, long-term performance in diverse conditions. To address these limitations and fully explore the high-precision potential of BDS-3 B1 and B2 WMSs, this paper presents a comprehensive performance evaluation through both theoretical analysis and experimental verification.
In terms of theoretical analysis, the thermal noise resistance and multipath mitigation capabilities of B1 and B2 WMSs will be analyzed through a combination of theoretical derivation and numerical simulation. It will be proved via theoretical analysis that compared to traditional narrowband receiving modes, the tracking jitter lower bounds of B1 and B2 WMSs can be reduced by approximately 64% and 43% respectively. Meanwhile, the multipath error envelope areas can be reduced by about 40% and 45%. These results indicate that B1 and B2 WMSs have significant high-precision positioning performance advantages compared to traditional narrowband signals.
For experimental verification, this paper will conduct dual-frequency, long-term, multi-scenario ranging, single-point positioning (SPP), and precise point positioning (PPP) experiments. The experiments will show that compared to traditional narrowband processing modes, the pseudorange measurement errors of B1 and B2 WMSs are reduced by 53% and 32% respectively under different elevation angle conditions. In open and complex scenarios, the average single-frequency SPP accuracy of B1 and B2 WMSs can be improved by 45% and 31% respectively. This research will also evaluate the performance of dual-frequency SPP and dual-frequency PPP for these two signals, with expected significant improvements in performance.
In conclusion, this research comprehensively evaluates the high-precision performance of BDS-3 B1 and B2 WMSs through theoretical analysis and experimental verification, demonstrating the enhanced positioning capabilities of BDS-3. The study shows that utilizing complex-value subcarriers in signal processing represents a significant advancement in GNSS receiver technology. The findings provide important references for the next-generation navigation signal structure design, receiver design, and multi-frequency multi-system positioning performance improvement.