What Is NB-IoT?

NB-IoT, or Narrowband Internet of Things, is a cellular radio standard designed for large numbers of simple devices that send small messages now and then. 3GPP, the body behind 4G and 5G, completed it in Release 13 in 2016 as LTE Cat-NB1, and Release 14 added Cat-NB2 with higher data rates and positioning.

An NB-IoT carrier is only 180 kHz wide, the size of a single LTE resource block. Operators can run it in three ways: standalone in its own spectrum, such as a refarmed GSM channel; in-band inside a normal LTE carrier; or in the guard band at the edge of an LTE carrier. Because it runs on licensed spectrum managed by the operator, it avoids the interference and duty-cycle limits of unlicensed low-power radios.

The standard keeps the radio simple. Devices are half duplex, messages are short and the network can repeat each transmission many times for a device with a weak signal. Those repetitions give NB-IoT around 20 dB more link budget than GPRS, enough to reach meters in basements, cabinets and underground chambers. NB-IoT and its sibling LTE-M are classed as low-power wide-area (LPWA) technologies, and 3GPP submitted both as part of 5G for massive machine-type communications, so they stay in service as networks move to 5G.

Battery life is the main reason to choose NB-IoT. 3GPP’s design target is around 10 years on a small battery for a device that sends a short message each day, though real life depends on signal strength, message size and how often the device wakes.

LTE-M (LTE Cat-M1) is the other LPWA option in the LTE family, and the choice between the two is the most common question once a project rules out a full LTE module. NB-IoT goes deeper into buildings and uses less power; LTE-M is faster, supports moving devices and can carry voice.

Many current modules support both, so a device can use whichever the local network offers. Our guide to cellular gateways and industrial cellular computers compares NB-IoT and LTE-M with the faster LTE categories and 5G.

In the USA, the main networks have closed or are closing their 3G services, and the government has said 2G will be switched off by 2033 at the latest. Machine-to-machine devices that used 2G, such as older meters, alarms and telemetry, are moving to NB-IoT, LTE-M or full LTE. USA operators have launched NB-IoT, LTE-M or both, and coverage varies by network, so check the operator’s map and roadmap for each site before choosing a module.

In the US, LTE-M has the wider coverage across the main carriers, and NB-IoT availability depends on the carrier. Roaming is also less settled than for normal LTE, so devices that cross borders are often better served by LTE-M or a module that supports both.

NB-IoT suits the edge of the network, not the middle. Devices that report a reading every few minutes or hours, run on batteries and never move are a good match: utility meters, tank-level and flood sensors, structural and environmental monitors, and the occupancy sensors behind smart parking systems. It does not suit video, large file transfers, frequent two-way control or anything that needs a reply in under a second.

Because NB-IoT sensors connect straight to the mobile network, they need no local gateway of their own. Industrial sites usually combine them with faster links: the sensors report over NB-IoT to a cloud or private platform, while the machines, cameras and controllers on site connect through industrial IoT gateways on Ethernet, 4G or 5G. Our overview of the industrial Internet of Things shows how those layers fit together.

We fit the cellular module, SIM holder and antennas in the industrial gateways and edge computers we supply as standard, and match the module category to the data each site has to send.