## 5 MPM-Based Interference Assessment
### Simulation Results  
The simulation studies were carried out using the MPM for the analyzed scenario and the adopted assumptions. The simulation results in the form of \(SIR\) and \(\Delta SIR\) versus beam separation angle are illustrated in Figures 10-13 for LOS and NLOS conditions, respectively.  
In general, under LOS conditions, for all analyzed models, the SIR increased with the increase in the beam separation angle. Characteristic local maxima occur for the 3 GPP reference and Sinc models. This is because the side lobes were included in the antenna pattern. Their location is related to the HPBW designated for the main lobe. The lack of side lobes in the Gaussian model significantly differentiates the nature of the obtained SIR curves. The proposed modification of the simple models ensures that the upward trend of \(SIR\) is maintained with the increase in \(\Delta\alpha\), similar to 3 GPP. In the case of the non-modified simple models, for \(\Delta\alpha>15^{\circ}\), we observed a downward trend.  
Figure 10: \(SIR\) versus beam separation angle under LOS conditions.  
Figure 11: \(\Delta\)_SIR_ versus beam separation angle under LOS conditions.  
Figure 12: _SIR_ versus beam separation angle under NLOS conditions.  
Figure 13: \(\Delta\)_SIR_ versus beam separation angle under NLOS conditions.  
In Figure 11, the \(\Delta SIR\) of the four analyzed models under LOS conditions are shown. Based on this, we can conclude that the modified Sinc model provides the most accurate representation of SIR relative to the 3 GPP reference model for all analyzed values of \(\Delta\alpha\). This fact is evident because the Sinc model (see Figure 6) provides an additional opportunity to reproduce the influence of side lobes.  
The advantage of the developed solution is evident in the NLOS scenario. In this case, the change in the \(SIR\) versus \(\Delta\alpha\) curve for the modified models is very similar to the curve for the reference model. Similar to the LOS conditions, the modification of the models produced an upward \(SIR\) trend for \(\Delta\alpha>25^{\circ}\). It should also be noted that the SIR curves for the 3 GPP and modified Sinc patterns coincide over the entire range of beam separation angles.  
Figure 13 depicts \(\Delta SIR\) versus \(\Delta\alpha\) for the four analyzed models under NLOS conditions. Compared to the LOS conditions, we can observe the clear effectiveness of the proposed modification. In the entire range of analyzed angles, the \(\Delta SIR\) error did not exceed 0.7 dB for the modified Gaussian, and for the modified Sinc, the maximum \(\Delta SIR\) error was no more than 0.1 dB.  
The RMSE and mean error (ME) metrics were the basis for the quantitative assessment of the comparative analyses. These metrics are determined by the expressions:  
\[RMSE\ (\text{dB})=10\log_{10}\sqrt{\frac{1}{N}\sum_{i=1}^{N}(SIR_{Model}( \Delta\alpha_{i})-SIR_{3 GPP}(\Delta\alpha_{i}))^{2}}, \tag{17}\]  
\[ME\ (\text{dB})=10\log_{10}\Biggl{(}\frac{1}{N}\sum_{i=1}^{N}\lvert SIR_{ Model}(\Delta\alpha_{i})-SIR_{3 GPP}(\Delta\alpha_{i})\rvert\Biggr{)}, \tag{18}\]  
where \(\Delta\alpha_{1}=0^{\circ},\ \Delta\alpha_{2}=0.1^{\circ},\ \ldots,\ \Delta \alpha_{N}=60^{\circ}\), i.e., \(N=601\).  
The results are shown in Table 3.  
The analysis of the obtained results shows that the modified Sinc provides the most accurate representation of the 3 GPP antenna pattern in the interference analysis under both LOS and NLOS conditions. In the NLOS scenarios, using the modified Gaussian modeling, only the antenna's main lobe may be sufficient to assess interference. This fact results from the small influence of the pattern's side lobes on the received power, which is related to the occurrence of multipath propagation and the lack of a direct path.