by Andy Slote - Mar 01 2022
Satellites provide another option for Internet of Things connectivity, contributing significantly to the goal of worldwide coverage. Recently, companies are deploying significant numbers of new satellites for IoT, with many more on the way. In addition, technological advances enable changes in design, configuration, and connectivity, promising to improve performance and reduce cost. However, satellite IoT is appropriate for specific use cases and requires a thorough evaluation like any network option.
The newest approach to satellite networks uses large numbers of small satellites, with some measuring around the size of a 10-centimeter cube. Providers launch many of these smaller types (typically hundreds) with different orbits to cover Earth with connectivity, with paths designed to create an environment where a sensor anywhere on Earth can connect to a satellite as quickly as possible.
Although there is occasionally a need for a connection over water (to a cargo ship, for example), most are, obviously, to points on land. The northern and southern extremes of the planet have little requirement for coverage. Still, many providers have chosen to launch polar-orbiting (meaning orbits passing over both poles) satellites, optimizing coverage as Earth rotates below. With water covering approximately 70% of the Earth, many will frequently be above areas where they receive little to no data. However, this configuration allows them to market “coverage anywhere on Earth.”
Data flows first from a device on Earth to a satellite and back down to a ground station. Routing to a cloud instance for processing is the typical next leg. Latency is inevitable and could be significant due to the need for an accessible satellite first to be overhead to receive device data with the same satellite requiring visibility to a ground station for the second data transmission, increasing time for routing to the destination.
Devices communicating with these satellites need a relatively clear, unobstructed view of the sky, so you can’t just put a device anywhere. Unfortunately, heavy tree cover, buildings, and other impediments can block the view to some, or all, of the satellites of a particular service.
Like with all satellite communication, weather conditions can also be a factor. Companies using the lower frequencies in the “L” band claim their transmissions are more effective during heavy cloud cover or storms than those using the much higher frequency Ka/Ku band.
Many of the recent IoT satellites launched are Low Earth Orbit (LEO), which means their orbits are between 180 km/110 miles and 2000km/1240 miles from the Earth. LEO satellites quickly complete a single orbit, accomplishing multiple per day. In addition, companies are launching LEOs for other purposes, like providing broadband Internet to underserved areas, for example.
As with many other connectivity options, leveraging satellites with other technologies can make sense. For example, a mobile device may use cellular networks until it moves out of range, at which time it will switch to a satellite to minimize data interruption. In addition, there are efforts to make satellites work seamlessly with land-based networks by using the same LoRaWAN or 5G protocols.
For the right applications (temperature readings in remote areas four times a day, for example), satellite connectivity can be a good choice for IoT. Evaluate your connectivity options thoroughly, considering hybrid solutions in your analysis while paying close attention to hardware and recurring costs.|