# Trends in LPWAN Technologies for LEO Satellite Constellations in the NewSpace Context
## 2 Satellite Constellations in IoT
#### Traditional Satellite vs. IoT Satellite  
The satellite design for IoT communications has been comprehensively investigated in the scientific literature, providing invaluable insights into the efficiency and cost optimization. Ref. [24] focuses on adapting satellites for IoT applications, characterized by low data rates, within a bandwidth of approximately one hundred kilohertz. These satellites, characterized by their compact dimensions and straightforward hardware-like half-wave dipole antennas, need advanced functionalities, such as beamforming or inter-satellite links. Furthermore, they operate in lower frequency bands, like very-high frequency (VHF) and \begin{table}
\begin{tabular}{c c} \hline
**Types of Satellites** & **Mass (kg)** \\ \hline Femtosatellites & \textless{}0.1 \\ \hline Picosatellites & 0.1–1 \\ \hline Nanosatellites & 01–10 \\ \hline Microsatellites & 10–100 \\ \hline Minisatellites & 100–500 \\ \hline Small Satellites & \textless{}500 \\ \hline Medium Satellites & 500–1000 \\ \hline Large Satellites & \textgreater{}1000 \\ \hline \end{tabular}
\end{table} 
Table 1: Classification of satellites based on their mass. ultra-high frequency (UHF), aspects influenced by the prevailing scientific literature on communication hardware design. In [27], scientific consideration is given to the efficiency and cost-effectiveness of small or nanosatellites. The proposal involves adopting 12U CubeSats arranged in a \(2\times 2\times 3\) configuration, orbiting at 500 km altitude. This scientific configuration is presented as a balanced solution, aligning with the findings from the scientific literature, meeting both cost and service requirements, and allowing the periodic access of IoT terminals to the satellites. Furthermore, ref. [28] outlines the hardware design considerations for IoT communication satellites. These considerations include the necessity for signal transmission and reception capabilities within suitable IoT application frequency bands, such as the L and S bands. Additionally, the requirement for antennas and signal processing systems enabling communication with IoT devices on the Earth's surface is emphasized. Given the substantial transmission distance in satellite communication, adequate power and signal amplification systems are essential to overcome increased path loss compared to typical terrestrial scenarios. Moreover, IoT communication satellites must effectively manage data frame repetitions, involving the capability to receive, process, and retransmit data from IoT devices operating in conditions of deficient coverage. Consequently, satellites should be equipped with data storage and processing systems to handle frame repetitions efficiently, enhancing the probability of successful data transmissions from IoT devices [29]. Additionally, the critical differences with traditional communication satellites lie in the emphasis on miniaturization, commercial technology utilization, and cost-effective design philosophies. Unlike their traditional counterparts, IoT satellites prioritize compact form factors, simplicity, and scalability, aiming to support low-data-rate applications efficiently. Table 2 compares the main features of the two satellite communication solutions.