## 3 Simulation Results  
### Base Scenario  
The processing steps required for 5G downlink data transmission are explained in Section 2. The system parameters used in the processing steps are listed in Table 1.  
Jammers may concentrate their RF energy into certain frequency bands using tone-type signals, or occupy a broader spectrum using chirp-type signals. Therefore, it is considered sufficient to examine the tone and chirp jammers in this study. First, in the no-jammer case, the RF power spectrum and EVM vs. RB are measured for the received signal, and the measurement results are shown in Figure 3. The observed fluctuations in the spectrum is caused by multipath fading. As explained in Section 2, an equalizer is used to minimize the fading effect on the received IQ symbols. To observe the effect of equalizer on the EVM data, EVM vs. RB is measured for both the unequalized and equalized IQ symbols, as shown in Figure 3b. The EVM vs. RB measurement obtained using unequalized IQ symbols directly reflects the fluctuation characteristics of the RF spectrum (red line in Figure 3b). On the other hand, the improvement brought about by the equalizer shows a decrease in the EVM data (blue line in Figure 3b). As shown in Equation (17), this improvement is expected. The same measurements are performed for different jamming cases, that is, tone and chirp jammers. Reviews related to tone jamming are given below, whereas repeated reviews for chirp jamming are provided in the Appendix A. The SJR parameter is selected as \(-5\) dB for both jamming conditions. The observed changes in the RF power spectrum and EVM after the application of these jamming signals are shown in Figures 4 and A1, respectively. In the EVM vs. RB data obtained using unequalized symbols, jamming effects are observed in addition to fluctuations owing to the fading (red lines in Figures 4b and A1b). On the other \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter Name** & **Value** & **Explanation** \\ \hline Carrier Frequency & 2.65 GHz & Frequency Range-1 for 5G \\ \hline MIMO Structure & \(8\times 2\) & \\ \hline MIMO Transmission Layers & 2 & \\ \hline Fading Channel Model & CDL-C & Urban Macrocell Model, NLOS \\ \hline OFDM Subcarrier Spacing (SCS) & 30 kHz & \(\mu=1\) (numerology) \\ \hline \multirow{2}{*}{Assigned RBs} & \multirow{2}{*}{51} & Transmission bandwidth close \\  & & to 20 MHz with the \\  & & 30 kHz SCS \\ \hline IQ Modulation & 16 QAM & \\ \hline Code Rate & 490/1024 & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Selected Data Transmission Parameters for the Base Scenario. Figure 3: No-Jammer Case, Obtained Throughput = %100 (BER = 0). (**a**) The Rx signal spectrum and (**b**) EVM vs. RB. hand, in the EVM vs. RB measurement taken with equalized symbols, the fluctuation is minimized owing to the equalizer, but jamming effects are still clearly observed (blue lines in Figures 4b and A1b)). Thus, in the EVM vs. RB data obtained with equalized symbols, jamming signals can be easily detected using a single threshold level, without considering any fluctuation effect in the data. Therefore, to avoid dealing with the fluctuation effect due to fading, EVM vs. RB measurement using equalized IQ symbols is proposed for jamming detection. In the next simulation, where the SJR is increased to 10 dB, the received signal is contaminated with jammers of the same tone and chirp type. The RF spectrum and EVM vs. RB measurements are shown in Figures 5 and A2, respectively. In this SJR case, the jamming signals cannot be detected using the RF power spectrum, which provides RSS information, as shown in Figures 5a and A2a. In addition, the throughput measurement for both the jamming cases is 100%, which means that the jamming effect cannot be sensed using this BER-based metric. However, the EVM vs. RB measurements successfully detect these small jamming signals, as shown in Figures 5b and A2b. This reveals the success of the proposed method in terms of sensitivity compared with RSS- and BER-based methods.