Internet of Things (IoT) via Satellite

Hybrid terrestrial-satellite systems require both in-depth understanding of terrestrial IoT and satellite communication. While it may appear attractive to use the same technology and waveforms for terrestrial and satellite communication, competing requirements and technical constraints – low power and low cost terrestrial communication in “unlicensed” bands below 1 GHz vs. PSD constraint and highly regulated satellite communication at frequencies above 10 GHz – favor a hybrid solution, optimized for “terrestrial” and “satellite”.

In addition to satellite communication, Fraunhofer IIS is also heavily engaged in providing technology, intellectual property and solutions for terrestrial IoT networks. This includes wireless sensor networks using s-net® technology and the wireless IoT solution mioty®. 

In IoT applications, often every minute is critical when time-sensitive information is transmitted via satellite and rapid responses are required. Small amounts of data can be transmitted quickly and easily, but with large data sets, transmission can become problematic: as the data volume increases, so does the transmission time.

Therefore, with our fully automated and self-regulating IoT systems, we span an ad-hoc network in which individual IoT devices can exchange and pool their computing power. The raw data collected is processed directly on-site using Artificial Intelligence and compressed to relevant information. The reduced amount of data can now be transmitted easily. In addition, not all IoT devices need to communicate with the satellite anymore, as a single device can transmit the calculation result.

Extreme Edge Computing offers significant advantages for Sat-IoT applications in terms of:

• Fast data transmission, as the processed data can be easily transmitted in combination with our mioty® protocol.
• Low latency on site, as distributed computing allows large amounts of data to be evaluated directly in the field. The result is immediately available locally.
• Energy efficiency, as the battery of the mobile IoT devices benefits from distributed computing and has a longer service life.

IoT devices need antennas with sufficient performance to bridge the distance between transmitter and receiver. Given the distance of several 100 kilometers between Earth and LEO satellites and up to 40000 kilometer to GEO satellites, such antenna designs are considerably challenging.

Size and complexity constraints prohibit the use of mechanically steerable reflectors or larger electronically steerable phased arrays for “Massive IoT” applications. Fortunately, compared to High-Throughput Satellite (HTS) that offer Internet services, throughput requirements for IoT are comparably low. This allows using small antenna apertures that provide adequate gain and beam steering capabilities while keeping antenna size, number of radiating elements and complexity of the excitation network low.

Fraunhofer IIS offers different antenna solutions for this use case, including

• Higher order mode patches with directivity optimized for modest elevation angles
• Multibeam antennas with several alternative pre-defined beam options
• Compact phased arrays, with cost-optimized phase shifters and a wide range of beam synthesis options

Considering “Massive IoT” applications over satellite, a large number of terrestrial terminals may concurrently transmit to the satellite. As these IoT terminals may share the same frequency band with other terminals transmitting to other satellites, care must be taken to ensure that the systems do not interfere with each other.

For most antennas, the beam width is indirectly proportional to the size of the antenna, i.e., a small footprint antenna has limited gain and directivity, thus produces a “wide” beam. This results in unwanted emissions toward adjacent satellites in the GEO orbit and other LEO or HEO satellites or terrestrial receivers. Therefore, to mitigate such harmful interference into other systems, direct-to-satellite IoT terminals need to comply with defined power spectral density (PSD) masks. Depending on beam width and pointing accuracy, such PSD masks significantly limit the permitted transmit power, link efficiency, system capacity and the number of IoT terminals in the network.

Fraunhofer IIS has devised a novel solution addressing the efficient use of spectrum and maximizing system capacity in such PSD limited scenarios, considering terminal and antenna type and pointing accuracy. Furthermore, a waveform implementing such concepts has been developed and is available in simulation.