# Challenges of Using the L-Band and S-Band for Direct-to-Cellular Satellite 5G-6G NTN Systems
## 5 Results  
An interference analysis involves significant amounts of both statistics and the use of distributions; therefore, the results of the studies are presented as the cumulative distribution functions (_CDF_) of several radio link performance and interference level metrics [21]. The values obtained during the simulation the of _C/N_, _C/(N + I)_, and _I/N_ values were used to generate _CDF_ distributions. First the data collected after the simulation comprised the probability distribution function (_PDF_). The _PDF_ can be integrated into the _CDF_ using the following formula  
\[CDF(X)=\int_{-\infty}^{X}PDF(x)dx \tag{10}\]  
The _PDF_ and _CDF_ data can be generated using the quantized data of the calculated values as a histogram \(H(i)\) in which \(I=\{0\ldots n\}\), and each value \(i\) can be mapped to a data value [21]\(x\) using the following expression:  
\[x(i)=x_{\min}+ix_{BinSize} \tag{11}\]  
Figure 10: Simulation of the interference from the 5G NTN system in the Immarsat system. The bin relating to data value \(x\) is then  
\[i(x)=Round\bigg{[}\frac{x-x_{\text{min}}}{x_{BinSize}}\bigg{]} \tag{12}\]  
The _CDF_ can then be generated from the histogram as a percentage using the following:  
\[CDF(X)=100\frac{\sum_{i=0}^{i(X)}H(i)}{\sum_{i=0}^{i(n)}H(i)} \tag{13}\]  
The pictures of the results are divided into two parts, (a) and (b), each providing specific information about the link performance and the receiver's noise level when the interference is present. In the first part, (a), the blue curve represents the _C/N_ levels at the input of the victim station during the simulation time, indicating the link performance in an interference-free environment. The orange curve represents the _C/(N + I)_ levels, revealing the link performance in the presence of interference caused by the 5G NTN satellite system. In the second part, (b), the graph displays different DeltaT/T values for the Immarsat receiver's noise level. This measurement indicates the ratio between the increased noise when interference is present and the noise level in the absence of external interference. Additionally, a punctured line is included in the graph, representing the threshold level at DeltaT/T = \(-\)12 dB. Figure 11 illustrates _CDF_ curves depicting the impact of the 5G NTN satellite system on the DeltaT/T and _C/N_ level degradation of an Omnispace mobile terminal receiver. The results obtained clearly indicate a significant degradation in the link performance of the Omnispace receiver when interference is present. The _C/N_ levels experience degradation between 6 and 8 dB 100% of time, and in some short periods, it can even reach 15 dB. Such a substantial degradation would have severe consequences, leading to either a tremendous degradation of the service quality or even a complete outage of the radio link. Additionally, it can be seen that the DeltaT/T threshold is exceeded by at least 16 dB and may reach 30 dB overall. Figure 12 illustrates _CDF_ curves depicting the impact of the 5G NTN satellite system on the DeltaT/T and _C/N_ level degradation of a Lyra mobile terminal receiver. Figure 11: CDF curves representing interference at the Omnispace receiver: (**a**) _C/N_ and _C/(N + I)_; (**b**) DeltaT/T. The results obtained clearly indicate a significant degradation in the Lyra link performance when interference is present. The C/N levels experience a degradation ranging from 1 dB to 10 dB; in spite of the fact that Lyra is a more interference-robust system, such degradation still may lead to radio link outages and serious delays in message delivery. Additionally, it can be seen that the DeltaT/T threshold is exceeded by at least 16 dB and may reach 28 dB overall. Figure 13 illustrates _CDF_ curves depicting the impact of the 5G NTN satellite system on the DeltaT/T and _C/N_ level degradation of an Immarsat Earth station receiver. The results obtained clearly indicate a significant degradation in the link performance of Immarsat when interference is present.