The most basic requirement of any IoT project is that all devices are connected, wherever they are located. While Wi-Fi, Bluetooth and terrestrial GSM networks are able to support many IoT applications, these cannot provide the ubiquitous, truly global coverage of satellites. 

Although an estimated 93.2% of the global population is covered by a mobile-broadband network 3G or above; there are many sparsely populated, remote areas, with important activities suited for IoT, which do not have terrestrial mobile or other forms of connectivity. 

Why is connectivity so important?

Lack of connectivity impacts operational efficiency, leaving organisations unable to reap the full value of their IoT solution. With 75% of businesses encountering connectivity issues during the proof of concept phase of their IoT project, connectivity, or lack thereof, is a vulnerability businesses must overcome. Satellite technology serves as a key enabler to transform IoT connectivity across industries and geographical borders. 

Types of satellite connectivity available to support IoT

There are three different types of satellite networks available: low earth orbit (LEO), medium earth orbit (MEO) and geostationary. Below we will explain the differences, highlighting the benefits and some common IoT use cases.

Source: Ground Control 

The diagram above shows the relative distance from Earth of the three satellite orbits, with low earth orbit (LEO) closest to the earth at 200 – 1,600km (373 – 932 miles), and geostationary orbit the furthest away, at 35,786 km (22,236 miles). Medium earth orbit (MEO) satellites are more rare; with just 10% of satellites orbiting between 5,000 – 20,000km from the earth’s surface.

LEO Satellites

LEO satellites orbit closest to the earth and are much smaller than their MEO and geostationary counterparts. Satellites in LEO are moving quickly, taking just 90 minutes to circle the earth. A single satellite moving at this speed would be unworkable for communication, as the ground stations on Earth would struggle to track the satellite’s location. For this reason, communications satellites in LEO create a constellation – multiple satellites that pass data between them, effectively creating a net around the earth. 

Often, the quality of connectivity will depend on the number of satellites in service within a LEO constellation. The more satellites, the more coverage and the better the constellation is able to mitigate signal interruption. As many IoT applications rely on consistent, frequent data transmission, the latter is particularly important. 

To reach a satellite in LEO, your signal can be lower powered, and the latency is comparatively low – less than 30ms. Simply, the data doesn’t have as far to travel to reach the satellite and vice versa, so transmission is faster and requires less power. 

What IoT applications are LEO Satellite networks commonly used for?

One benefit of LEO satellite constellations is that you don’t have to point your signal in a particular direction; it will get picked up by one of the satellites and passed through the mesh back to the ground station without you needing to adjust the angle of your antenna. That makes these networks well suited for the handling of non-stationary IoT applications, such as refrigerated transport, weather balloons or data buoys.

In addition, LEO satellites are a viable option for environmental and asset monitoring applications, which send small data packages. The low-cost setup usually requires one IoT device per modem, and service reliability is very high.

Interestingly, Martin Keenan, Technical Director at Avnet Abacus, states that the combination of 5G networks and LEO coverage in particular, “is likely to become increasingly relevant for industrial internet of things (IIoT) deployments in the very near future.”

Network providers include: Iridium, Globalstar, Orbcomm and SpaceX.

Geostationary satellites

In contrast, satellites in geostationary orbit are moving at the same speed as the planet, and so appear to be stationary to us. As they’re in much higher orbit, they can ‘see’ much more of the earth, so fewer satellites are needed to cover a large territory.

In comparison to LEO satellites, geostationary satellites have a longer lifespan in space. So constellations are in operation for decades and are capable of continuously updating and upgrading their software – making them stable technology partners. However, geostationary networks typically have higher service bills and require more frequent maintenance.

Geostationary satellites usually boast large solar panels, which support the high-power output required for data transmission. As the data has further to travel with geostationary networks, latency is also a little slower, roughly 100ms. But this usually equates to less than two seconds for the data to be sent, and redirected to the ground station, which is more than adequate for IoT applications. 

What IoT applications are geostationary satellite networks commonly used for?

Geostationary satellites are more efficient for broader coverage. While they are more expensive to set up, these costs are predictable, and the operating costs are often lower, thanks to a high signal throughput meaning multiple IoT devices per modem is possible. As such, these networks are often well suited for applications requiring real-time updates, for example condition and location monitoring, SCADA telemetry and monitoring backhauls. 

Network providers include: Inmarsat, Eutelsat, and Astra (Sky).

MEO-Satellites

As mentioned above, MEO satellites are relatively rare and are used almost exclusively for GPS and navigation related services. MEO satellites orbit the earth at higher altitudes than those in LEO and therefore provide a greater coverage area. To put this into perspective, a company with 24 MEO satellites in service will usually have four covering any given spot on the earth at any one time. This means that MEO satellite providers are able to mitigate outages caused by extreme weather and / or obstructive objects.

Often MEO satellites are described as a compromise between the advantages of LEO and geostationary satellites. While a constellation is still required for continuous coverage, fewer satellites are required when compared to LEO constellations. Moreover, these constellations operate with a lower latency than their geostationary equivalents. 

What IoT applications are MEO satellite networks commonly used for?

MEO satellite services are not widely commercially available for IoT applications. They are used for GPS, maritime navigation and crew communications. More recently, they have been deployed to deliver low latency, high bandwidth data connectivity to service providers, government agencies and commercial enterprises, supporting network backhaul and humanitarian relief operations. 

Network providers include: SES.

IoT data transmission via satellite connectivity

Although there are clear differences in the orbiting patterns of the three types of satellite networks, all broadly conduct data transmission in the same manner. An IoT device sends (and in some cases also receives) data to the satellite through its antenna. This is then directed to ground stations (sometimes known as earth stations), where all data from the satellite constellation is sent, and from there, is transmitted to your base of operations, using the internet. Finally, there is an endpoint for users to view the IoT data and ultimately enable organisations to successfully manage their IoT project. 

Ultimately, selecting the right satellite network type for any IoT solution is dependent on many factors, including location and mobility of IoT devices, and expected volume and frequency of data transmission. But satellite solutions augment terrestrial services with high efficiency and service levels, making them a natural complement to terrestrial IoT networks, and as mentioned, a key enabler to transform IoT connectivity.