## 4 Experimental Setup and Results
### Initial Measurements  
The first scenario was when the receiver was located near the cell. Figure 6 displays the received signal level measured for a downlink frequency of 793.5 MHz. The level of signal received was \(-\)76.8 dBm, which corresponded to the proximity of the cell's base  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Crt. No.** & **R [m]** & **SIR [dB]** \\ \hline
1 & 1 & 33.63 \\ \hline
2 & 1.5 & 26.59 \\ \hline
3 & 2 & 21.59 \\ \hline
4 & 2.5 & 17.72 \\ \hline
5 & 3 & 14.55 \\ \hline
6 & 3.5 & 11.87 \\ \hline
7 & 4 & 9.55 \\ \hline
8 & 4.5 & 7.50 \\ \hline
9 & 5 & 5.67 \\ \hline
10 & 5.5 & 4.02 \\ \hline
11 & 6 & 2.51 \\ \hline
12 & 6.5 & 1.12 \\ \hline
13 & 7 & \(-\)0.17 \\ \hline
14 & 8 & \(-\)2.49 \\ \hline \hline \end{tabular}
\end{table}
Table 3: SIR values calculated for different distances.  
station. Additionally, Figure 7 shows the resource block measured on the central frequency of 793.5 MHz with a bandwidth of 5 MHz.  
By applying Formula (6), the path loss \(PL(\mathrm{dB})\) was calculated at a 1 m distance as being \(-33.238\) dBm. Subsequently, using Formula (7) with the received signal level (RSRP) of \(-79.5\) dBm, we determined a signal-to-interference ratio (SIR) of \(-33.63\). This calculation indicates that jamming the downlink connection in the condition of good signal strength was confirmed by the experiment.  
Figure 8 presents the signal level measured on the uplink connection corresponding to an uplink frequency of 834.5 MHz, which was measured at \(-81\) dBm; this is illustrated in green in the waterfall window and corresponds to the vicinity of the cell. We could conclude that the smartphone that was next to the cell emitted less power at the uplink frequency thanks to the signalling procedure in which the smartphone revealed its location in the network. As a result, the power level was adjusted, considering the network, to be lower.  
Figure 9 presents the received signal level measured for a downlink frequency of 793.5 MHz, which was measured at \(-94.1\) dBm and corresponded to the edge of the cell coverage. It is shown in Figure 9 that the resource block measured on the central frequency was 793.5 MHz with a bandwidth of 5 MHz. Applying Formula (6), the path loss \(PL(\mathrm{dB})\) was calculated at a 1 m distance to be \(3-3238\) dBm, and the SIR, which was calculated  
Figure 8: Uplink measurement in the vicinity of the cell.  
Figure 7: Downlink measurement in the vicinity of the cell.  
with Formula (7) for the signal level of the RSRP of \(-94.1\) dBm, was \(-19.514\). The value of the SIR was below the minimal value of the limits presented above for an LTE connection. Therefore, jamming in this condition can successfully affect the communication channel.  
Figure 10 presents the signal level measured on an uplink connection corresponding to the uplink frequency of 834.5 MHz, which was measured at \(-55.8\) dBm when the smartphone was transmitting to the network in a data session. We could conclude that a smartphone that was at the edge of the cell emitted more power at the uplink frequency because of the signalling procedure in which the smartphone revealed its location in the network, and thus, the power level was increased in accordance with the network.  
Figure 11 illustrates the setup used for the experimental jamming on the downlink connection in the real case scenario (Digi Mobil smartphone presented in Figure 6), where the RSRP was \(-79.5\) dBm. A radio monitoring spectrum analyser Nestor TSMA 6 was used to discover and measure all available frequency bands and the technologies provided at the radio-monitoring point. A list of all available frequencies was obtained and provided to the Hack-RF to prepare the jamming frequencies.  
Figure 10: Uplink measurement at the edge of the cell coverage.  
Figure 9: Downlink measurement at the edge of the cell coverage.