Interference Analysis of BeiDou Short Message on GPS L1 Receiver and Mitigation Based on Cascaded Hybrid Blanking Algorithm

The Beidou Short Message Service (BDS-SMS) user equipment transmits signals in the frequency range of 1610 MHz to 1626.6 MHz, which is adjacent to the Global Positioning System (GPS) L1 operating frequency band. Currently, reports from general aviation aircraft indicate that GPS positioning is interrupted when BDS-SMS is in use. BDS-SMS interference exhibits broadband characteristics, making it challenging to mitigate. To ensure the robustness of GPS L1 under BDS-SMS interference, it is essential to quantitatively analyze its impact on GPS L1 and develop targeted mitigation methods. An experimental testing platform is built to analyze the impact of BDS-SMS signals on tracking, pseudorange, positioning, and integrity utilizing data from a commercial receiver. The platform also determines tolerable interference thresholds and the minimum safe antenna spacing for specific scenarios. A comb filter is integrated into the existing hybrid blanking algorithm, and a targeted notch frequency adaptive adjustment method is introduced, based on power spectrum estimation and resampling. To verify the performance of the proposed algorithm, GPS L1 analog signal data is collected under real BDS-SMS interference. The Carrier-to-Noise Ratio (CNR), code tracking error, and positioning error are analyzed with different mitigation algorithms, including pulse blanking, Continuous Wavelet Transform (CWT), notch filter, and hybrid blanking. The results show that the proposed cascaded hybrid blanking algorithm achieves highest CNR, the lowest code tracking error, and smallest positioning error. Specifically, when the proposed algorithm is applied, the mean CNR increases by 8-10 dB, and the positioning error decreases by an average of 20 m compared to when no mitigation algorithm is applied in the experiment. This study contributes to the development of new broadband or multi-frequency interference mitigation algorithms, enhancing the robustness of airborne GNSS receivers.