Satellite navigation authentication method based on the combination of Interplex and CSK

To enhance the anti-spoofing capabilities of satellite navigation systems, this study proposes a novel signal authentication method that integrates Interplex modulation with Code Shift Keying (CSK). The authentication signal is modulated using CSK and introduced as an input signal for Interplex modulation. This signal is then phase-modulated onto a common carrier alongside the navigation signal, thereby maintaining a constant envelope for transmission. On the receiver side, the embedded authentication signal is demodulated to verify the authenticity of the received signal, enabling the identification of spoofing attempts. Under the constraint of fixed total transmission power, introducing an authentication signal reduces the power allocated to the original navigation signal. Using GPS L5 signal as a case study, this paper demonstrates how to control the C/N₀ degradation of a navigation signal by adjusting Interplex modulation coefficient, and how to vary the authentication information rate through CSK parameter tuning. Experimental results reveal that, under equal C/N₀ degradation, the proposed method achieves significantly higher authentication data rates than binary phase modulation approaches.