A novel digital threat model and effect analysis on modernized BeiDou signals

There exists deformation among the signals which could threaten the position accuracy and integrity of Global Navigation Satellite Systems (GNSS). A "2nd-Order Step" threat model was developed to model anomalous signal deformation for BPSK signal and then it was extended to the BOC signal. With the advent of new GNSS like BeiDou system, the research on the threat model has been experiencing a new upsurge. Generally, the classic threat model for digital distortion assumes that the failure acts directly on the "sub-chip" generation. Thus, for BOC signal, it is unable to characterize PN code deformation and subcarrier deformation independently and needs an improvement. This paper proposes a novel digital threat model on modernized BeiDou signals. In order to characterize different digital deformations independently, it defines three failure modes: TMA-1, TMA-2 and TMA-3, which is respectively used to describe the digital distortion caused by PN code failure, subcarrier failure and both two. For BeiDou system, the mathematical model of B1C data is firstly established. In addition, the Power Spectral Density (PSD) is also taken into consideration. In order to evaluate the impact of the digital deformations on modernized BeiDou signals, code-tracing accuracy and ranging bias based on new threat model are also analyzed.