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How to choose between NB-IoT and Cat M

How to choose between NB-IoT and Cat M - what's the difference

As network deployments of both NB-IoT and Cat M continue, designers have a wider choice than ever before when it comes to the connectivity they select for their projects. NB-IoT and Cat M offer compelling advantages for specific types of deployments, with each having unique strengths. However, limitations influence design and global coverage for each must be considered, along with device volumes, power and cost constraints.

NB-IoT and Cat M - what's the difference?

NB-IoT is a standards-based low power wide area (LPWA) technology designed to enable a wide range of new IoT devices and services. NB-IoT significantly improves the power consumption of user devices, system capacity and spectrum efficiency, especially for indoor coverage. Battery life of more than ten years is a feature that makes this technology particularly attractive for long-life applications including smart meters. The extended coverage and ultra-low device complexity of NB-IoT and the fact that initial cost of the NB-IoT modules is expected to be comparable to GSM/GPRS are further advantages.

Cat M, sometimes known as LTE-M, has been developed to support massive IoT. The main benefit is Cat M devices operate on much smaller frequency bands (1.4MHz) which enables more devices to be connected at each cell site. This makes the technology particularly effective for dense IoT deployments which require a large number of devices to connect in a small area. A typical LTE cell can support ten times the number of active Cat M devices in comparison to full LTE devices. Again, Cat M devices use less power than other cellular options and can come with advanced power saving features. In addition, they can be highly cost effective as an alternative to LTE modems.

It's fair to say both NB-IoT and Cat M offer IoT organizations something new because they offer a cost-effective form of connectivity that has minimized power requirements while still offering either very high device density per cell or strong indoor coverage. Both technologies have their advantages, but these must be stacked against local availability, which remains patchy. This will change as the market for each matures and coverage becomes more widespread. Then, it becomes a simple choice of matching the attributes to the deployment characteristics.

Which should I choose? Ask the Quexperts

A recent Quectel Masterclass on Cat M and NB-IoT design tips provides excellent help for deciding which technology to select. It highlighted the relative merits of each in contrast to LTE and is particularly useful for designers who are assessing how optimize their designs for either technology. The session also provided design tips for each technology and shared design indications for the Quectel BG95. In addition, the Masterclass delivered an update on current world coverage status for both NB-IoT and Cat M and shared the key differences between Cat M and NB-IoT.