# An Accurate GNSS Spoofing Detection Method Based on Multiscale Eye Diagrams
## 4 Detection Coverage Simulation Experiment
This effectively blocks the influence of the noise power and ensures that the sensitivity of spoofing detection is maintained. Furthermore, as the relative power of the spoofing signal increases, the detection rate of the SQM metric gradually decreases. This is primarily because, when the spoofing signal is very similar to the authentic signal and has considerable power, the spoofing signal will rapidly influence the receiver. The receiver's phase-locked loop quickly disengages from the authentic signal and locks onto the spoofing signal, resulting in a modification of the duration of the slope change in the receiver's correlation peaks. The greater the similarity of the spoofing signal and the higher the relative power advantage, the faster the intrusion, and the shorter the duration of the abnormal correlation peak slope. Since the SQM metric relies heavily on changes in the correlation peak slope, the decrease in anomaly duration ultimately leads to a decrease in the detection rate. The CN0-based detection method is less affected, and the detection rate basically remains between 30% and 40%. The EDDM-MSC-MMP method proposed in this article is not affected by this, and, except for the lower detection rate under the conditions of lower relative power advantage, \(\Delta\theta_{s}=0.7\pi\) and \(\Delta\theta_{s}=1.3\pi\), it maintains a detection rate of over 95%. To conduct a more objective evaluation of the performance of the detection method, a new metric, called 'detection coverage', is established. In contrast to the detection rate, the detection coverage provides insight into the ratio of the detectable volume to the total volume within a specified detection area. This ratio can comprehensively reflect the detection method's capacity to identify spoofing signals with varying relative power advantages, code phase delays, and carrier phase delays. A minimum acceptable detection rate, designated \(P_{\min}\), is established. If \(P_{d}>P_{\min}\), the area is classified as detectable; otherwise, it is designated as undetectable. In our experimental setup, the detection area for each experiment was 1 unit of volume, and the entire experimental volume comprised 4410 units. The detection coverage was defined as follows:  
\[\text{Detection coverage}=\frac{\text{Volume of detectable area}}{\text{Total volume}} \tag{20}\]  
The result for \(P_{\text{min}}=80\%\) is presented (Figure 5). The yellow indicates detectable areas, while the dark blue indicates undetectable areas. The measurement of the detection coverage enables the effective evaluation and optimization of the overall performance of the detection system. A statistical analysis was conducted to determine the coverage of each detection method on the basis of varying minimum acceptable detection probabilities (Table 2). Regardless of whether SQM single-metric or SQM composite-metric detection is employed, the high similarity of spoofing signals results in a detection coverage of less than 10% when \(P_{\text{min}}>90\%\), which is considered inadequate. No significant distinction can be observed between the various SQM metrics. Only when \(P_{\text{min}}<50\%\) does the number of detectable regions increase for some SQM metrics, such as Ratio and Ratio+ELP. None of the CN0-based spoofing detection methods demonstrate optimal performance  
Figure 4: Detection rates with respect to the possible relative power advantages, code phases, and carrier phases of the spoofing signal (\(C/N_{0}=\)1 to 10 dB, \(\Delta\tau_{s}=\)0 to 1 chip, and \(\Delta\theta_{s}=\)0 to 2\(\pi\) rad) with \(T_{d}=\)1s. From top to bottom, the rows of the subplots correspond to \(C/N_{0}\), ELF, Delta, Ratio, Slope, Slope+Delta, Ratio+ELP, and the EDDM-MSC-MMP. The light yellow indicates a detection rate of 100%, whereas the dark blue indicates a detection rate of 0%. when \(P_{\min}\geq 50\%\). Instead, there is only a limited increase in the number of detectable regions until \(P_{\min}<30\%\).