## 3 Experimental Scenario and Specifications
### Antenna Configuration  
In this study, all satellite payloads are assumed to be mounted on a 1U CubeSat platform (100 \(\times\) 100 \(\times\) 100 mm). To meet the strict volume and mass budgets of both the CubeSat and IoT endpoint devices, we implemented a rectangular patch microstrip antenna specifically designed for this work on a 100 mm \(\times\) 100 mm FR4 substrate. According to [PERSON] et al. [33], whereas existing Rogers Duroid-based designs achieve up to 2.6 dB gain, a patch microstrip antenna designed on the same FR4 substrate exhibits 1.992 dBi gain. In this paper, considering the short lifespan and economic constraints of LEO/VLEO \begin{table}
\begin{tabular}{l c c c} \hline \hline
**Parameter** & **LoRa** & **NB-IoT** & **Miqty** \\ \hline Frequency (MHz) & 920 & 1995 & 920 \\ Bandwidth (kHz) & 125 & 180 & 100/200 \\ Bit rate (bps) & 2604 & 15,000 & 2380 \\ Receiver sensitivity (dBm) & \(-125\) & \(-141\) & \(-139\) \\ Modulation & CSS & \(\pi/2\)-BPSK & (G)-MSK \\ Required \(E_{b}/N_{0}\) (dB) & 6.8 & 6.9 & 3.6 \\ Average delay (s) & 8-10 & 1.5-10 & 16 \\ Maximum number of concurrent devices & 1200 & 50,000 & 1,000,000 \\ Power consumption (mJ/bit) & 0.993 & 0.25 & 0.01 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Communication specifications of LPWAN technologies. \begin{table}
\begin{tabular}{l c c c} \hline \hline
**Specification** & **LoRa** & **NB-IoT** & **Miqty** \\ \hline Tx power (\(P_{\text{Tx}}\)) & 20 dBm & 23 dBm & 14 dBm \\ Tx antenna gain (\(G_{\text{Tx}}\)) & 2.14 dBi & 5.51 dBi & 2.14 dBi \\ Tx feeder loss (\(L_{\text{Tx, feeder}}\)) & 0.2 dB & 0.2 dB & 0.2 dB \\ Tx other loss (\(L_{\text{Tx, other}}\)) & 0.4 dB & 0.4 dB & 0.4 dB \\ Rx antenna gain (\(G_{\text{Rx}}\)) & 2.14 dBi & 5.51 dBi & 2.14 dBi \\ Rx feeder loss (\(L_{\text{Rx, feeder}}\)) & 0.2 dB & 0.2 dB & 0.2 dB \\ Rx other loss (\(L_{\text{Rx, other}}\)) & 0.4 dB & 0.4 dB & 0.4 dB \\ System temperature (\(T_{\text{sys}}\)) & 693.7 K & 446.7 K & 583 K \\ Feed offset (x, y) (mm) & (30, 21) & (16.28, 6.51) & (30, 21) \\ Patch antenna size (L x W) & 90 \(\times\) 63 mm & 70 \(\times\) 28 mm & 90 \(\times\) 63 mm \\ Ground plane size (L x W) & 100 \(\times\) 100 mm & 100 \(\times\) 100 mm & 100 \(\times\) 100 mm \\ \(G/T\) (dB/K) & \(-26.27\) & \(-20.98\) & \(-25.51\) \\ Noise figure (NF) & 6 dB & 6 dB & 5 dB \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Specifications of satellite and ground stations for LPWAN technologies. CubeSats, we selected an FR4-based patch microstrip antenna based on these experimental results, and within the limited \(100\,\mathrm{mm}\times 100\,\mathrm{mm}\) footprint, we optimized the parameters to tailor antennas for each communication band (\(920\,\mathrm{MHz}\) for LoRa and Mioty and \(1995\,\mathrm{MHz}\) for NB-IoT) [34]. Moreover, the \(1.6\,\mathrm{mm}\)-thick FR4 substrate offers low cost and compatibility with standard PCB processes, with short-term space qualification demonstrated in similar CubeSat studies. Furthermore, in this section, we focus on gain, among various antenna performance metrics (e.g., return loss, VSWR), as the primary goal of this study is to select a single antenna that maximizes the link margin between the CubeSat and small IoT devices in an IoT-NTN LPWAN environment. In particular, for LPWAN-based IoT-NTN applications involving CubeSats and ground devices, gain is considered the most critical factor compared to other performance metrics. Antenna Design and Gain Optimization  
LoRa and Mioty both operate in the sub-\(1\,\mathrm{GHz}\) ISM band (\(920\,\mathrm{MHz}\) for South Korea). Therefore, a patch microstrip antenna was designed on a \(100\,\mathrm{mm}\times 100\,\mathrm{mm}\) FR4 substrate. To determine the optimal antenna size, MATLAB simulations were conducted by varying the patch width and length between \(50\,\mathrm{mm}\) and \(90\,\mathrm{mm}\).