Direct-To-Satellite IoT - A Survey of the State of the Art and Future Research Perspectives

Abstract

The Internet of Things (IoT) has drawn an enormous attention into the scientific community thanks to unimaginable before applications newly available in everyday life. The technological landscape behind the implied surge of automated interactions among humans and machines has been shaped by plugging into the Internet very low power devices that can perform monitoring and actuation operations through very cheap circuitry. The most challenging IoT scenarios include deployments of low power devices dispersed over wide geographical areas. In such scenarios, satellites will play a key role in bridging the gap towards a pervasive IoT able to easily handle disaster recovery scenarios (earthquakes, tsunamis, and flash floods, etc.), where the presence of a resilient backhauling communications infrastructure is crucial. In these scenarios, Direct-to-Satellite IoT (DtS-IoT) connectivity is preferred as no intermediate ground gateway is required, facilitating and speeding up the deployment of wide coverage IoT infrastructure. In this work, an in-depth yet thorough survey on the state-of-the-art of DtS-IoT is presented. The available physical layer techniques specifically designed for the IoT satellite link are described, and the suitability of both the current Medium Access Control protocol and the upper layer protocols to communicate over space links will be argued. We also discuss the design of the overall satellite LEO constellation and topology to be considered in DtS-IoT networks.

A Survey on Technologies, Standards and Open Challenges in Satellite IoT

“…A direct access from the MTD to the satellite is a more appealing solution in scenarios which are lacking infrastructure deployments or with a low density of MTDs. This variant is supported by [17], [33] and shown in Fig. 2 as the remote logistics scenario.…”

“…Once a suitable satellite is reached, a wireless satellite-to-ground link is then used to deliver uplink messages/collect downlink messages from a ground station. It is also possible that uplink (downlink) messages are stored and carried by the serving satellite until a suitable ground station (the target MTD) is in sight [33]. Finally, the IoT services are connected to ground stations thanks to a terrestrial link, e.g., in optical fiber.…”

“…Of course, in such a last case, the issues related to latency should be carefully taken into account. Moreover, the configuration of a direct connection from nodes to satellite has recently gained momentum with respect to the indirect configuration in many recent papers [17], [33] as well as recent commercial initiatives, which will be surveyed in the next pages. Finally, the implementation of satellite backhauling via ISLs (i.e., the so-called switching in the sky) is rather challenging [13], thus it should be carefully exploited, mainly for wide-area IoT network deployments where the message delivery delay is bounded and the serving satellite is not in the line of sight with any ground stations before the delivery deadline has expired.…”

A Deep Reinforcement Learning Based Approach for Energy-Efficient Channel Allocation in Satellite Internet of Things

“…In this paper, we consider direct mode, which is used in Direct-to-Satellite IoT (DtS-IoT). Compared with indirect mode, direct connection is a more appealing way in some specific scenarios [4]. For example, in some remote areas with very low node density, it is not worth to set a gateway.…”

On the scalability of battery‐aware contact plan design for LEO satellite constellations

“…In this context, Delay‐Tolerant Networking (DTN) has been leveraged in order to render a better utilization of communication opportunities by means of storing, carrying, and forwarding data 8 . The DTN approach is particularly valuable for providing connectivity to ( i ) partially deployed mega‐constellations which cannot leverage traditional Internet routing before the complete topology is connected in orbit and ( ii ) sparse constellations for Earth observation and high‐latency data relay systems (i.e., Internet of things [IoT] 9 ). To fully exploit DTN, efficient contact plans need to be derived on ground in advance and timely provisioned to the constellation 10 …”