# Challenges of Using the L-Band and S-Band for Direct-to-Cellular Satellite 5G-6G NTN Systems
## 3 Materials and Methods
\begin{table}
\begin{tabular}{c c c c} \hline
**Parameter** & **Rural-eMBB-s** & **Rural-mMTC-s** & **Rural-HRC-s** \\ \hline Terminal type & Handheld & MTD & Handheld \\ Satellite orbit & & Handheld & \\ configuration & & LEO, 600 km altitude & \\ Spot beam pattern & & Hexagonal pattern; at least 19 spot beams. & \\ Service link & & 2 GHz & \\ frequency & & & \\ Channel bandwidth & 30 MHz & 30 MHz & 180 kHz-3 MHz \\
3 dB beam width & & 4.41 degrees & \\ Satellite EIRP density & & 34 dBW/MHz & \\ Satellite antenna gain & & 30 dBi & \\ Satellite G/T & & 1.1 dB/K & \\ Device deployment & & 100\% outdoors; randomly and uniformly distributed over the area. & \\ UE density & 10 UEs per spot beam. & At least 500 per km\({}^{2}\) & 10 UEs per spot beam. \\  & Fixed and identical speed of & & \\  & 250 km/h of all UEs, & & Fixed and identical speed of \\ UE mobility model & randomly and uniformly & & 30 km/h of all UEs, \\  & distributed direction. & Stationary & randomly and uniformly \\  & For all other evaluations: & & distributed direction. \\  & Stationary. & & Message size of 32 bytes: \\  & & 1 message/day/device & \\  & & or & \\ Traffic model & Full buffer & 1 message/2 h/device & Full buffer \\  & & Packet arrival follows Poisson arrival & \\  & & process for non-full buffer system-level & \\  & & simulation & \\ UE antenna height & & 1.5 m & \\ \hline \end{tabular}
\end{table} 
Table 2: Example parameters used in evaluations for handheld and MTD terminals. Figure 1: NTN typical scenario according to 3 GPP TR 38.821.  
will be provided by the NTN and coverage requirements. In our study, we considered a constellation of 448 satellites with 89 degrees of inclination; it should be noted that for contiguous coverage in practice, there could be a much greater number of satellites, so from the standpoint of protecting incumbent systems from the NTN interference our assumption may be considered optimistic. Orbital characteristics are presented below in Table 3.  
STK software was used for the simulations, and the satellites were simulated using the orbital parameters from Table 2 and the transmitting parameters from Table 1. Figure 2 presents simulation of the typical NTN constellation. Based on Table 1, the satellite's service area is comprised of a hexagonal shape with a minimum of 19 spot beams. In our study, we simulated 19 spot beams for each satellite. However, it is important to note that to prevent interference between adjacent beams, spot beams are usually divided by frequency. Therefore, in our study, we assumed that only four randomly selected beams per satellite were sources of interference. Figure 3 illustrates the approximation of the antenna pattern of a single beam and provides a model of 19 beams antenna pattern. The 3 GPP and ITU-R reports do not provide any particular antenna pattern for a beam; therefore, for a beam antenna pattern recommendation, we turned to the ITU-R S.1528 [15], since it is the most commonly used pattern for NGSO mobile satellite simulations below 30 GHz. To implement the antenna in accordance with the approximations provided in the ITU-R Recommendation S.1528 and characteristics in Table 2, an antenna size between 2 and 2.5 m would be required; it should be noted that this \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Type of the orbit & Circular \\ Altitude & 600 km \\ Number of orbital planes & 14 \\ Number of satellites per plane & 32 \\ True anomaly phasing & 11.25 degrees \\ RAAN increment & 25.7 degrees \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Orbital parameters of the simulated 5G satellite NTN. Figure 2: Simulation of the 5G-6G NTN constellation. size is based on theoretical expressions, assuming an efficiency between 0.55 and 0.65, and in practice, the size of the antenna may vary slightly at the production stage.