Direct-to-satellite communication for the Internet of Things (IoT) has attracted significant interest from both the scientific community and major telecommunications players. The integration of satellite connectivity in smartphones and IoT devices promises a transformative impact on critical applications such as environmental monitoring, asset tracking, agriculture, and nature conservation. These applications require reliable and energy-efficient technologies for transmitting sensor data from regions without terrestrial networks, necessitating robust design of waveforms and protocols. This work investigates the most suitable IoT protocols for direct-to-satellite communication, emphasizing overhead, spectral, and energy efficiency. By introducing a framework and evaluation metrics that incorporate physical layer overhead into the evaluation, a comprehensive analysis of the effective energy efficiency in satellite IoT systems is conducted. Our findings highlight substantial differences among the Low Power Wide Area Network (LPWAN) protocols. Consequently, we propose a new classification for the most energy-efficient protocols, termed Massive Multiple Access very Low Power Wide Area Networks (MMA-vLPWANs). This classification aims to streamline the selection process for energy-conscious satellite IoT waveforms for deployments in remote areas. The results not only advance the understanding of protocol efficiency in satellite IoT communications but also offer a guideline for optimizing power usage in IoT devices, extending their operational life and enhancing their utility in inaccessible regions.     «

Direct-to-satellite communication for the Internet of Things (IoT) has attracted significant interest from both the scientific community and major telecommunications players. The integration of satellite connectivity in smartphones and IoT devices promises a transformative impact on critical applications such as environmental monitoring, asset tracking, agriculture, and nature conservation. These applications require reliable and energy-efficient technologies for transmitting sensor data from re...     »