Release 17 of the 3GPP standard improves support for NB-IoT and non-terrestrial networks. This is referred to as scenario 4 or, by those involved, satellite scenario. Constellations of low-earth orbit (LEO) satellites will be able to handle NB-IoT (narrow-band IoT) traffic as defined by the 5G standards, without modification.
Any IoT device with cellular connectivity will be able to connect and communicate with satellite constellations equipped with 5G cell tower technology. The IoT device needs no modification or special antenna. In fact, the device may not even know it is operating over a non-terrestrial network. Non-terrestrial networks (NTNs) are now being created to deliver truly ubiquitous connectivity. To learn how and why, Avnet spoke with Gianluca Redolfi, Chief Business Officer of Sateliot, one of the pioneers in this area.
How do you put 5G in space?
In the past, commercial cellular networks have been human-centric. That changed with IoT. But there is a mismatch between cell tower deployment and the location of connected devices. More devices are being used in remote locations. Greater 5G coverage is needed to support them.
Coverage must be extended to areas that can’t be serviced by conventional networks. 3GPP members recognize this and are working toward a fix.
The network being deployed by Sateliot is based on nanosatellites. A nanosatellite is a general term to describe any satellite that weighs up to 10kg. Each nanosatellite includes a payload, which in this case is the 5G cell tower. Sateliot is working with partners to build and launch the nanosatellites but developed the payload itself.
The company’s LEO satellites orbit the planet at 24,000 kilometers per hour, at a height of 600 km. it takes around 90 minutes to complete an orbit, so multiple satellites are needed to provide near constant coverage.
Anything put into orbit is exposed to extreme temperature variations, radiation and space-borne effects such as solar winds and meteorite fragments. Sateliot has designed its nanosatellites to survive space for around five years.
Gianluca Redolfi explained that the company has plans to build an NTN of 256 nanosatellites. This would provide enough coverage to enable IoT devices anywhere on the surface to connect to the network once every minute.
The NTN complies to the 3GPP standards. Each satellite in an NTN should provide connectivity for up to 50,000 NB-IoT devices. With this capacity, Redolfi sees no problem with the Sateliot network supporting the massive IoT. If the network approaches capacity, the company can add more satellites. “We have authorization to go up to 500,” Redolfi said.
What is massive IoT?
Massive IoT is the point when cellular technology and IoT come together. Massive IoT describes the kind of devices that need simple but reliable and low-cost internet connectivity. Delivering that connectivity creates new opportunities. It is massive because there could be hundreds of billions of devices connecting in this way.
Redolfi explained that Sateliot’s core target market is the massive IoT. This may include ecological solutions such as avalanche monitoring or wildfire prevention. It will also cover agricultural applications like monitoring cattle grazing on remote plains. Commercially, it will change the way logistics and supply chain companies operate by providing continuous monitoring of assets, wherever they are in the world.
“Massive IoT requires two things: very affordable devices, or sensors, and very affordable connectivity,” Redolfi said. Users can expect to pay $1 per month or less to keep each device connected.
Low-cost sensors, around $2 each in Redolfi’s estimation, must also be low power. They will be expected to operate for as much as five years without maintenance, which includes a change of batteries. Although perhaps not as harsh as space, sensors used in the massive IoT could also be exposed to extreme conditions.
Cellular networks for massive IoT
Previous generations of cellular connectivity have been used to supplement IoT operations. The technologies implemented in 5G are expected to change the landscape. Narrow-band communications was conceived with data in mind. It provides the right mix of bandwidth and reliability needed by IoT.
The issue remains coverage. But with NTNs now being realized, coverage may not be an issue any longer. This is where Sateliot and companies like it will fit. Redolfi believes his company has a significant head start on others.
“We are using different companies. We have our own internal team, and altogether this is enough for us to build the first satellite constellation on this standard. We are the first one, and we are probably a couple of years ahead of anyone else,” said Redolfi.
Redolfi believes the cellular network model is ready for disruption. Currently, network providers attract subscribers, sell equipment designed for their network and retain customers through contracts linked to their services. This may work for people, but he feels companies with connected devices have different requirements.
The Sateliot business model is to partner with terrestrial network providers. The Sateliot network will act like any other network for customers with a roaming contract. When their device isn’t able to connect to a cell tower locally, it will automatically switch to a satellite cell tower.
“We sell our connectivity wholesale to the carriers of the world, providing extension of coverage for narrow-band IoT to their customers,” Redolfi said.
Non-terrestrial networks for massive IoT
The 3GPP consortium has been working on NTN standardization since 2017 with a Study Item (SI) in Release 15. The potential for non-terrestrial 5G networks covers use-cases that come under both the enhanced mobile broadband (eMBB) and massive machine-type communications (mMTC) service enablers. For IoT applications, mMTC is the core focus. NB-IoT comes under mMTC.
NTNs are intended to provide network continuity for devices that are moving in and out of coverage from terrestrial cell towers. However, satellites move at speeds of around 7.5 km/s. The amount of time a device will have to communicate with a cell tower in space could be as little as around 6.5 seconds.
This time will vary. If the satellite generates a larger beam, it will have a larger footprint. A larger footprint means longer coverage. The 3GPP standard also discusses LEO satellites at heights of 600 km and 1,200 km, as well as geostationary satellites at 35,786 km. These factors mean the area of the beam of an LEO will typically be between 100 km and 1,000 km. One-way latencies for LEOs will be around 30 ms to 50 ms.
The beam may be fixed or moving, which will also influence the time in coverage. Beam-steering technology provides for two scenarios. In the moving-beam scenario, the beam covers a fixed area, so the footprint on the surface moves with the satellite. In fixed-beam scenario, the beam is steered so its footprint is maintained for as long as its position in orbit allows.
There are many other considerations and design challenges covered by the 3GPP standards. Overcoming these has enabled NTNs to develop and we are now at the point of large-scale deployment. The massive IoT will no doubt need to rely on these NTNs if it is to meet expectations.
It may sound extravagant to provide cellular coverage for IoT applications using satellites. But the falling cost of technology and the increased access to space makes it feasible. The 3GPP consortium has been working toward this for many years. Many companies are part of the effort to make NTNs a viable proposition.
The lifetime of a nanosatellite is around five years. In that time, it will have provided connectivity for countless IoT devices. When the satellite is ready to be replaced, the standards and the technology will have improved. The replacement will be even more capable, and we will likely have already become dependent on its service.
Sateliot is currently offering free trials of its satellite network. Sign up here.