## 5 IoRT Systems Based on Space-Borne NTN Networks
### Enhanced Throughput/Transmission Rate  
Although the implementation of satellite connectivity for IoRT devices shows potential, it also poses difficulties in terms of spectrum management for 5G satellite networks. In \begin{table}
\begin{tabular}{l l l} \hline \hline
**Ref.** & **NTN Architecture** & **Description** \\ \hline
[89] & LEO & Development of a beam-hopping-based satellite system for IoT that can support extensive coverage with fewer transmitters and offers flexibility to cope with time-variant traffic distributions. \\ \hline
[90] & Generic & Development of solar-powered satellite access points to provide energy autonomy and reliable internet connectivity in areas with irregular electricity supply. \\ \hline
[91] & LEO & Study of satellite coverage variations due to latitude shift. \\ \hline
[92] & LEO-Cellular & Development of a novel gateway placement algorithm that considers channel conditions and service demand distribution to optimize network resource utilization and coverage. \\ \hline
[93] & LEO & Development of a modeling framework for IoT-over-satellite access systems that aims to maximize link availability while minimizing interference. \\ \hline
[94] & GEO & Development of a NOMA multibeam satellite IIoT architecture in Ka-band to extend coverage to devices located in remote areas. \\ \hline \hline \end{tabular}
\end{table} 
Table 5: IoRT systems based on space-borne NTN networks: **enhanced coverage and availability**. response to these challenges, ref. [95] presents an innovative, dynamic spectrum management scheme that is tailored to this particular context. The effectiveness of the proposed scheme in spectrum management for machine-to-machine and human-to-human communications in 5G satellite networks is demonstrated by simulation results on throughput, delay, spectral efficiency, and fairness index. NB-IoT, a promising technology for Low-Power Wide-Area Networks (LPWANs), enables widespread deployment of IoT services. However, in remote areas, terrestrial coverage gaps necessitate the integration of LEO satellites as a supplementary network layer. However, the inherent differential Doppler shift associated with satellite communication can degrade system performance. Authors [96] delve into the NB-IoT over LEO satellite architecture, where the satellite provides NB-IoT connectivity to fixed NB-IoT terminal equipment located beyond the reach of terrestrial infrastructure. To address the significant differential Doppler among terrestrial user channels, the authors propose a resource allocation scheme that effectively mitigates excessive Doppler values. Specifically, they propose segmenting the coverage area into smaller sub-regions, ensuring that the differential Doppler within each region remains within permissible limits. A phased-array antenna framework for IoT-over-satellite applications leveraging nano-satellites is presented in [97] to facilitate global IoT connectivity in remote areas. The proposed approach enables precise beamforming toward targeted IoT devices, boosting received signals while minimizing interference from other terrestrial devices. By efficiently sharing radio spectrum resources, this approach enhances capacity. A practical implementation of this framework involves fabricating an X-band phased array antenna, which has been validated through gain pattern and return loss testing, confirming its feasibility. In the realm of the satellite-based Internet of Things, efficient access for numerous sensors and short-burst transmissions remains a challenge. To address this issue, ref. [98] proposes a time-slot random access protocol employing Walsh codes specifically tailored for sink node scenarios. A load estimation-based, dynamic Walsh code selection mechanism is introduced to optimize system throughput. Simulation results demonstrate the protocol's effectiveness in enhancing system throughput under high load conditions while effectively managing resource utilization during periods of medium and low demand.