Xiaowei Cui

The sine-BOC (binary offset carrier) modulation is used in several signals of the new European Global Navigation Satellite System, Galileo, and modernized GPS. It provides these signals with enhanced robustness against multipath and increases the precision of the range measurement. However, this modulation presents some drawbacks. The most severe is the ambiguity problem in acquisition and tracking, which introduces a large bias in the pseudo-range measurement. In order to solve this problem, an unambiguous tracking technique for sine-BOC signals is proposed. This technique is based on a pseudo correlation function (PCF) which does not have any side peak and thus completely removes all of the false lock points on the discriminator output. Impacts of thermal noise and multipath on the proposed technique are investigated. Theoretical and numerical results obtained with BOC(n,n) and BOC(2n,n) signals show that this technique has a good noise mitigation performance and an average multipath performance.

With the completion of the experimental and regional phases, China's BeiDou Navigation Satellite System (BDS) is being speedily expanded to a global and multifunctional satellite navigation system, BDS III. Confronted with challenges such as limited frequency resources and diversified user requirements, new signals with novel modulation techniques are adopted in BDS III. In addition to the legacy B1I and B3I signals, new open service signals, B1C and B2a/B2b, as well as some new authorized service signals, will be broadcast by BDS III satellites. Among them, B1C and B2a are compatible and interoperable with GPS and Galileo. The modulation techniques and the detailed signal structures of B1C and B2a are introduced in this paper, along with analysis of the initial in-orbit test results of the new signals.

Localization systems utilizing Ultra-WideBand (UWB) have been widely used in dense urban and indoor environments. A moving UWB tag can be located by ranging to fixed UWB anchors whose positions are surveyed in advance. However, manually surveying the anchors is typically a dull and time-consuming process and prone to artificial errors. In this paper, we present an accurate and easy-to-use method for UWB anchor self-localization, using the UWB ranging measurements and readings from a low-cost Inertial Measurement Unit (IMU). The locations of the anchors are automatically estimated by freely moving the tag in the environment. The method is inspired by the Simultaneous Localization And Mapping (SLAM) technique used by the robotics community. A tightly-coupled Error-State Kalman Filter (ESKF) is utilized to fuse UWB and inertial measurements, producing UWB anchor position estimates and six Degrees of Freedom (6DoF) tag pose estimates. Simulated experiments demonstrate that our proposed method enables accurate self-localization for UWB anchors and smooth tracking of the tag.