# Performance Analysis of NB-IoT Uplink in Low Earth Orbit Non-Terrestrial Networks +
## 6 Numerical Results
### Link Budget Simulation  
The link budget simulation shows the results for one day using Equation (16). \(SNR_{required}\) is the minimum SNR that satisfies \(BLER\leq 0.1\) and \(SNR_{required}\) depends on \(N_{dunrs}\). Figure 11b shows the minimum \(SNR_{required}\) for different \(N_{dunrs}\); 3.7 dB for \(N_{dunrs}=1\), 2 dB for \(N_{dunrs}=2\) and 2.3 dB for \(N_{dunrs}=3\). \(SNR_{received}\) is calculated through Equation (15) and the parameters used in the simulation are summarized in Table 6. The link budget simulation calculates  
Figure 12: Uplink transmission \(BLER\) result according to \(TBS\) with various numbers of \(DMRS\) symbols. Doppler shift = 950 Hz, (**a**) \(TBS\) = 296 bit, (**b**) \(TBS\) = 328 bit. Figure 13: Uplink throughput for different numbers of \(DMRS\) symbols per slot with one or two HARQ processes. (**a**) One HARQ process, (**b**) Two HARQ processes  
\(LM_{i}\) every 30 s through a 3D satellite orbit simulation implemented in MATLAB. The LEO satellite used in this study is a STARLINK satellite and the STARLINK satellite orbit is implemented using the TLE file. TLE references the North American Aerospace Defense Command (NORAD) [29]. To see the effect of adding _DMRS_ symbols, we set the number of satellites and the number of satellite orbits as variables. The number of satellites is set from 1 to 27 per orbit, and simulations are performed in 1 and 6 orbits. This study assumes that a maximum of 27 satellites can be deployed in one orbit by setting the minimum interval for continuous communication of LEO satellites. The inter-satellite spacing is set in two ways according to the arrangement method of the LEO satellites. In the first method, called fixed-spacing, the inter-satellite spacing does not change with the number of satellites. Inter-satellite spacing is set as the interval when there are 27 satellites equally spaced in one orbit. The second method, called variable-spacing, is that as the number of satellites increases, the spacing between satellites becomes narrower, and the spacing is the same as in the first method when there are 27 satellites. In other words, the satellites are uniformly filled around the perimeter of an orbit. Figure 14 shows the implemented 3D satellite orbit. Figure 14a shows 27 satellites \"STARLINK-1671\". The spacing between each satellite is the same, and as the number of satellites decreases, the spacing increases. Figure 14b shows 162 satellites \"STARLINK-1671\", \"STARLINK-1298\", \"STARLINK-2498\", \"STARLINK-1625\", \"STARLINK-2299\", and \"STARLINK-1139\" [29]. The time set in the simulation is from 22 February 2022 to 23 February 2022, and all satellites have the same parameters. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **Value** & \\ \hline Transmit power & \(-6.99\) dBW & 200 mW -\(>\)10 log(0.2) \\ Transmit antenna gain & 0 dBi & Antenna gain \\ EIRP (effective isotropic & \(-6.99\) dBW & Transmit power + antenna \\ radiated power) & \(-6.99\) dBW & gain \\ Atmospheric loss & 0.07 dB & [21] \\ Shadow fading margin & 3.00 dB & \\ Scintillation loss & 2.20 dB & \\ Polarization loss & 0.00 dB & \\ Additional losses & 0.00 dB & \\ [PERSON]’s constant \([k]\) & \(-228.6\) dBW/K/Hz & \\ Bandwidth \([\)B\(]\) & \(52.55\) dBHz & \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Link budget simulation parameters. Figure 14: 3D satellite orbits implemented in MATLAB [44]. (**a**) one orbit (27 satellites), (**b**) six orbits (162 satellites). Figure 15 shows the \(P_{OTR}\) result. The lower \(P_{OTR}\) can be achieved using fewer satellites when using variable-spacing rather than fixed-spacing. Therefore, performance analysis is focused on variable-spacing. Figure 15 presents the result of one orbit. In one orbit, the simulation is implemented by adding three satellites each. Increasing the number of \(DMRS\) symbols improves the performance of \(P_{OTR}\) by about 5%. However, in one orbit, even if the number of satellites is increased, it is more than 70%, so it is difficult to give a significant meaning.