Satellite Positioning Signal Authentication Narrowband Segmentation
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Solution Overview
Problem
GNSS receivers are vulnerable to spoofing by smart jammers that can mimic satellite signals using the same spreading code, leading to incorrect data being used for navigation and timing applications, especially when the jammer's signal strength exceeds that of the satellite's signal.
Innovation Solution
A narrowband (NB) signal is transmitted in addition to the standard wideband (WB) signal, with NB signal segments time and frequency hopped according to a unique pattern unrelated to the WB signal's spreading code, allowing for authentication and secondary time and position determination without relying on the compromised WB signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a smart jammer uses the same spreading code as the GPS satellite, then the jammer can spoof the satellite signal, but the GPS receiver cannot distinguish between the satellite signal and the jammer signal
Solution Approach 1:
The patent segments the authentication function from the main navigation signal by introducing a separate narrowband authentication signal. This authentication signal uses a different code (authentication code) than the spreading code used for navigation data, allowing the receiver to verify signal authenticity independently of the navigation signal processing. The segmentation enables the system to detect and reject spoofed signals without compromising the main navigation function.
Solution Approach 2:
The patent introduces an intermediary authentication signal that acts as a mediator between the satellite and the receiver. This narrowband signal carries authentication information that verifies the identity of the transmitting satellite. The receiver uses this intermediary signal to confirm signal legitimacy before processing the main wideband navigation signal, thereby preventing spoofing attacks.
2Measurement precision
If the GPS receiver uses coherent correlation to improve signal-to-noise ratio, then the receiver gains better signal detection, but data bit phase changes can severely degrade the correlation results
Solution Approach 1:
The patent separates the authentication function from the navigation signal processing by using a distinct narrowband signal with its own correlation process. This segmentation allows the authentication correlation to operate independently without being affected by data bit phase changes in the navigation signal. The narrowband signal uses a different code structure that is not modulated by the navigation data bits, thus avoiding the degradation issue.
Solution Approach 2:
The patent employs periodic narrowband authentication signals transmitted at specific intervals within the signal frame structure. These periodic authentication signals allow the receiver to perform regular authentication checks without continuously processing the full wideband signal, reducing the impact of data bit phase changes while maintaining reliable signal verification.
3Ease of operation
If the GPS receiver relies solely on the wideband signal for position determination, then the system is simpler to operate, but the system becomes vulnerable to jamming and spoofing
Solution Approach 1:
The patent segments the signal processing into two independent paths: one for authentication (narrowband) and one for navigation (wideband). This segmentation allows the receiver to maintain relative simplicity by processing each signal type through its dedicated path, while the combination of both paths provides enhanced reliability. The authentication path verifies signal legitimacy without complicating the navigation processing.
Solution Approach 2:
The patent implements preliminary authentication using the narrowband signal before the receiver processes and relies on the wideband navigation signal. This preliminary action verifies signal authenticity in advance, preventing the receiver from processing spoofed or jammed signals. The authentication check is performed first, ensuring that subsequent navigation processing is based on legitimate signals only.
Data Source
AI summary
A receiver authenticates a wideband (WB) signal from global navigation satellites (GNSS) using a narrowband (NB) signal that is also transmitted from the satellites. The NB signal includes segments that are transmitted in time and frequency slots of successive transmission frames. The NB signal is less susceptible to a smart WB jammer. Also, the NB signal segments may also be transmitted at a relative power level with respect to the WB signal, where the relative power level may vary in a known pattern so as to distinguish the WB signal of the satellite from a stronger WB signal from a smart jammer.