## 3 GNSS Signal Disruption Simulation
### GNSS Signal Quality Monitoring Setup  
In this paper, the GNSS signals are recorded using a Skydel simulated satellite signal, represented in the form of in-phase (I) and quadrature-phase (Q) components. These signals are combined using a 2:1 combiner with various types of signal disruption generated by the simulator's advanced interference tool environment. The RTL-SDR RF front end is utilized to digitize the signals at a specified sampling rate. To record the files, we can specify the sampling frequency, centre frequency, duration of the recording, etc. The default settings are a centre frequency of 1575.42 MHz, a sampling rate of 2.9 MSPS, 1024 samples per frame, and a duration of 300 s. The file format is int16 in the baseband frequency, separated into two.dat files, where each one is int8. The order of the signal recording is as follows: the first file is the in-phase (I) samples, and the second one is the quadrature (Q) samples. The total number of samples is 32,676, acquired in one millisecond, with a bandwidth of 2 MHz [50].  
The digitized signals are then processed through GNSS receiver modules, including acquisition, tracking, navigation solution, and position calculation. The experimental setup for the GNSS signal under different disruptions is depicted in Figure 1a,b.  
The L1 GNSS signal is expressed by  
\[S_{L1}=A_{p}\cdot P(t)\cdot D(t)\cdot\cos(2\pi f_{1}t+\varphi)+A_{c}\cdot C(t) \cdot D(t)\cdot\sin(2\pi f_{1}t+\varphi), \tag{1}\]  
where \(S_{L1}\), \(A_{p}\), and \(P(t)\) denote the L1 signal frequency, the amplitude, and the phase of the P(Y) code, respectively. \(D(t)\) corresponds to the navigation message, \(f_{1}\) is the frequency of the L1 carrier, \(\varphi\) is the initial phase, and \(A_{c}\) and \(C(t)\) are the amplitude and phase of the  
Figure 1: (**a**) Skydel CSG-8 GNSS simulator setup for recording jamming and spoofing signals, (**b**) Various GNSS disruption recording setups and post-processing using GNSS SDR.  
C/A code, respectively. The nominal GNSS signal in the time domain, its spectrum, and its spectrogram recorded through an RTL SDR are depicted in Figure 2a.  
Figure 2: _Cont._  
Continuous Wave Interference (CWI)  
The CWI-affected GNSS signal is given by  
\[CWI=\exp{(j2\pi f_{cw}t)}, \tag{2}\]  
where \(f_{cw}\) and \(t\) represent the centre frequency and period of interference, respectively. The CWI power level is varied from 10 to 60 dB and the centre frequency is set as 1575.42 MHz. Plots of the signal simulation in the time and frequency domains, its spectrum, and the spectrogram recorded for 25 dB can be seen in Figure 2b.  
The pulse type of interference signal is denoted by  
\[PI=\sqrt{P_{j}}\;\;p_{\tau}(t)\otimes\sum_{k=1}^{K}\delta\bigg{(}t-\frac{k}{f_ {rk}}\bigg{)}.\exp{\bigg{(}j2\pi f_{jk}t\bigg{)}}, \tag{3}\]  
where \(\sqrt{P_{j}}\) and \(p_{\tau}(t)\) are the signal power and the pulse signal of the duty cycle (\(\tau\)), respectively. \(f_{rjk}\) is the pulse repetition frequency, \(\delta\) is the Dirac pulse, and \(\otimes\) is the convolution operator. Here, the pulse repetition frequency is 10,000 Hz, the duty cycle  
Figure 2: (**a**) Clean GNSS signal in the time domain and its spectrum in the frequency domain recorded using RTL SDR. (**b**) CWI GNSS signals in the time domain and its spectrum in the frequency domain recorded using RTL SDR. (**c**) Pulse interference GNSS signal in the time domain and its spectrum in the frequency domain recorded using RTL SDR. (**d**) Chirp interference GNSS signal in the time domain and its spectrum in the frequency domain recorded using RTL SDR.  
is 20%, and the signal power is fixed at 25 dB to record the signals in both the time and frequency domains, as shown in Figure 2c.  
Chirp Interference (CI)  
The mathematical expression for CI is given as follows:  
\[CI=\exp(2\pi\frac{k}{2}t^{2}+2\pi f_{0}t). \tag{4}\]  
A bandwidth of 10 MHz and a sweeping time of 100 \(\upmu\)s are set to record all events under chirp interference, as can be seen from Figure 2d.