## 5 Simulation Results with Parabolic Equation Modeling
This fundamental equation, known as the link budget [55], assumes that all quantities are expressed in decibel units:  
\[P_{r}=P_{t}+G_{t}+G_{r}-L. \tag{33}\]  
Assuming an antenna gain of \(G_{r}=0\) dBi at the reception point, and substituting Equation (32) into Equation (33) in place of \(P_{r}\), then replacing \(10\log_{10}(S)\) with the expression obtained from Equation (31), and finally rearranging the resulting equation, we obtain:  
\[E_{\text{dB}\mu V/\text{m}}=P_{t}+G_{t}-L-20\log_{10}(\lambda)-19.01+145.76. \tag{34}\]  
Taking into account that \(\lambda=\frac{\zeta}{f}\), it follows that \(20\log_{10}(\lambda)=20\log_{10}(c)-20\log_{10}(f)\), where \(20\log_{10}(c)=169.54\), and thus the following expression can be written:  
\[E_{\text{dB}\mu V/\text{m}}=P_{t}+G_{t}-L+20\log_{10}(f)-42.79. \tag{35}\]  
If the frequency is to be specified in MHz \(\left(20\log_{10}(10^{6})=120\right)\) and ERP is used for the calculations \(\left(\text{EIRP}=P_{t}+G_{t}=\text{ERP}+2.14\right)\), then the following formula should be implemented:  
\[E_{\text{dB}\mu V/\text{m}}=\text{ERP}_{\text{dBm}}-L+20\log_{10}(f_{\text{ MHz}})+79.35. \tag{36}\]  
The field strength levels and their distribution obtained through parabolic equation modeling at 3.6 GHz can be examined in Figures 13 and 14, while the results of the 6 GHz simulations are shown in Figures 15 and 16. The maximum, minimum, and range values obtained from the PEM simulations for individual test scenarios, along with the differences between them, are summarized in Table 5.  
Considering that PEM is applicable to both frequency bands under study, and that the simulation parameters were identical for both investigations, it is possible to compare the model's simulation results as a function of frequency. The difference between the results at 6 GHz and 3.6 GHz is illustrated in Figure 17.  
In general, lower electric field strength values were obtained at 6 GHz than at 3.6 GHz. This is consistent with the theory, which states that with increasing frequency, the path loss  
Figure 16: Distribution of field strength values, 6 GHz, Parabolic equation Modeling. Figure 17: Differences between the 6 GHz and 3.6 GHz simulations (Parabolic Equation Modeling). \[P_{r}=10\log_{10}(S)+20\log_{10}(\lambda)+G_{r}+19.01. \tag{32}\]0 Distribution of field strength values, 3.6 GHz, Parabolic Equation Modeling. \[P_{r}=10\log_{10}(S)+20\log_{10}(\lambda)+G_{r}+19.01. \tag{32}\]1 Field strength level values around the investigated base stations (PEM, 6 GHz). also increases, resulting in lower received power levels. This effect is not compensated by the positive frequency-dependent term in the equation linking received power to electric field strength (36), as is evident from the results, particularly from the data shown in \[P_{r}=10\log_{10}(S)+20\log_{10}(\lambda)+G_{r}+19.01. \tag{32}\]2 It can be seen that although the maximum electric field strengths near each base station remained approximately the same--and even slightly increased due to the \(20\log_{10}(f_{MHz})\) term in (36)--the minimum electric field strengths were significantly lower at 6 GHz. It is clear that the maxima occur at test points located close to the base stations, where the distance is short and terrain effects are minimal, whereas the minima occur at greater distances, where path loss is significantly influenced by terrain and increased distance. It is also observable that in the case of TestBS_2, the difference between the maximum and minimum values is considerably smaller than in the other two cases. This is because, for this base station, Line-of-Sight (LOS) conditions are ensured at all test points, so the path loss is predominantly a function of distance and is minimally affected by the terrain. The simulation results for this base station also reveal that the difference between the maximum and minimum field strength values at 3.6 GHz and 6 GHz deviates by only approximately 5.37 dB--a significantly smaller variation compared to the other two base stations.