There are seemingly limitless connectivity options for IoT projects these days. Satellite networks are being used to provide connectivity from the sky. To build a satellite-enabled IoT solution, OEM integrates a satellite IoT modem into their product. That allows OEM customers to connect to the IoT satellite network; depending on the IoT solution architecture and value chain, OEM can offer a user dashboard with IoT data or use a white-labeled solution from the network provider or a third party.
Here is a high-level overview of satellite networks used in IoT solutions.
Naturally, all satellites use orbits — orbits can be as high as thousands of kilometers above the Earth’s surface (geostationary orbit GEO), all the way down to hundreds of kilometers (low-earth orbits LEO).
Massive GEO-satellites sit on the geostationary orbit, allowing them to rotate in sync with our planet. GEO-satellites always “look down” on the same big area, called footprint. Typically, a GEO-satellite network consists of very few satellites — a constellation that connects the whole globe.
- big solar panels — high power output into an IoT link down to Earth
- powerful antennas — a lot of data can be sent up and down
- uninterrupted IP link with the receiver on the ground — a continuous flow of IoT data
Geo-satellites are in operation for decades and they can continuously upgrade their software, which means a reliable technology partner for an OEM that buys into the satellite service. The perks are balanced out by a high service bill that customers pay for a slice of the GEO network.
On the other end of the satellite service spectrum are the compact (sandwich-box to shoe-box in size) LEO-satellites that occupy low-earth orbits or a sun-synchronous orbit.
Their path above the globe might look like a knife peeling an apple, a gradually shifting signal footprint that eventually revisits the same spot with a given cadence. LEO satellite footprint is also relatively small compared to the bigger GEO-sibling — only a few hundred kilometers. Sattelite network providers mitigate signal interruption as an LEO-satellite moves away by having a big constellation of LEO-satellites with smooth signal handover. This includes:
- Small satellites have a shorter lifespan in space — network providers need a lot of them to have a reliable operation
- they have a smaller energy supply — the signal received and sent down is lower in power
Luckily, the signal latency is also lower due to the shorter distance from the surface, which helps in critical IoT applications.
The quality of the service depends on the number of satellites in service — if the number is low the link is interrupted for a longer period of time and IoT data is collected with time gaps.
LEO satellite IoT network and solution providers include Myriota, Kineis, Astrocast, Kepler Communications, SWARM technologies (bought by SpaceX), Starlink (in a very low orbit), Orbcomm, Iridium.
Anything in-between the orbits of GEO and LEO satellite is Medium Earth Orbit MEO-satellites. In my experience, MEO-satellite services are used for maritime navigation and crew communications, therefore not serving many IoT-related use-cases just yet. However, naval logistics is going to win a lot from it.
Getting the Signal Back Down to Earth
While the space segment differentiates a lot per each network type, the ground part of each network is roughly similar: an IoT device with a satellite antenna that transmits IoT sensor data (and receives control commands) and a satellite dish (a local data sink for any satellite) that connects to the network. The network delivers IoT data to the data center and, eventually, there is an endpoint for a user to view the IoT data. Because all of the different types of satellite connectivites work the same from the earth the type of satellite used depends on how the satellite’s position will help the solution from the air.