# Situational Awareness: Mapping Interference Sources in Real-Time Using a Smartphone App
## 5 In-Laboratory Tests and Calibrations
### Spectral Detection with Wideband Interference  
In the first experiment a wideband jammer, visible in Figure 3, was employed. It features eight RF outputs, covering different frequencies, including the GNSS L1 band. The power of the generated  
Figure 3: In-laboratory test setup.  
wideband noise, measured over the GNSS FE bandwidth with a spectrum analyzer connected via RF cable, was \(-60\) dBm (Figure 4).  
The jamming source was wired to attenuators in order to control its power with respect to the GNSS signal. Two kinds of attenuator were used: a variable attenuator (\(0\div 20\) dB) with 1 dB resolution and two fix attenuators (10 dB and 20 dB). Once attenuated, the jamming signal was combined with the GNSS signal coming from a rooftop antenna. The mixed signal was then sent to the SiGE v3 FE [48], which outputs a 16.368 MHz digitalized signal modulated at intermediate frequency of 4.092 MHz, as indicated in Table 1. This sample stream is processed in real-time by NGeneApp.  
We started the test with maximum jamming power, then we decreased the power with \(-5\) dB step using the attenuators, to determine the minimum in-band interference power level whose effect is non-negligible.  
The effect of the jammer has been evaluated both on the PSD of the received signal and on the receiver capability of acquiring, tracking and computing the PVT. Figure 5 summarizes the obtained results in terms of PSD estimation for different level of the interfering power: the green plot represents the obtained PSD when the jammer is on, while the black one is the interference-free PSD. When the jammer power is not attenuated (Figure 5a), the PSD is totally distorted, and the spectral distortion increases dramatically in the whole bandwidth; in this case, the GNSS signal is disrupted and the receiver cannot operate. Till \(-80\) dBm (Figure 5b), the jamming signal has a relevant effect to the receiver performance: when the jammer is turned on, the tracking of some satellite is lost, while some others experience a drop in the C/N\({}_{0}\) level. No tracking anomaly happens when the jamming level is lower than \(-85\) dBm, but the application is still able to detect the distortion of the spectrum if the interference power is greater than \(-95\) dBm (Figure 5c) where a small distortion in the left side of the spectrum is still visible. Only below \(-105\) dBm (Figure 5d), no distortion is detectable. Based on these observations, the detection threshold for the TE metric was set to 50,000 units. These test results are summarized in Table 3.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**WB Jammer Power** & \(-60\) dBm & \(-80\) dBm & \(-85\) dBm & \(-95\) dBm & \(-105\) dBm \\ \hline
**TE (Total Energy of** & & & & \\
**Error) (dB/Hz)\({}^{2}\)** & 235,828 & 163,683 & 119,806 & 13,612 & 8409 \\ \hline
**Receiver Signal** & \(\bigtimes\) Disrupted & \(\bigtimes\) Severely compromised & \(\bigvee\) Slightly affected & \(\bigvee\) Unaffected & \(\bigvee\) Unaffected \\ \hline
**TE Threshold (dB/Hz)\({}^{2}\)** & & & 50,000 & & \\ \hline
**Interference Detection** & YES & YES & YES & NO & NO \\ \hline \hline \end{tabular}
\end{table}
Table 3: Wideband interference: in-lab test results.  
Figure 4: Spectral analysis of the jammer on the L1 band (**a**) and zoomed-view (**b**).