nRF9160 supports LTE-M (Cat-M1) and Narrowband Internet of Things (NB-IoT) (Cat-NB1/Cat-NB2). Both technologies are used for low-power cellular Internet of Things (IoT) but have some significant differences based on particular use cases.
| Features | LTE-M | NB-IoT | |
|---|---|---|---|
| Also known as | LTE CAT-M1, Enhanced Machine Type Communication (eMTC) | LTE Cat-NB1 (3GPP rel 13) | LTE Cat-NB2 (3GPP rel 14) |
| Bandwidth | 1.4 MHz | 200 kHz | 200 kHz |
| Max throughput (DL/UL) | 300/375 kbps | 30/60 kbps | 127/169 kbps |
| Latency | 50-100ms | 1.5-10s | |
| Typical range | <11 km | <15 km | <15 km |
| Mobility/cell reselection | Yes | No | Limited |
| Roaming | Yes | Limited | Limited |
| Deployment density | Up to 50 000 per cell | Up to 50 000 per cell | Up to 50 000 per cell |
| Battery lifetime | Up to 12 years1 | ||
The biggest difference between LTE-M and NB-IoT is the offered data rate or how much time you spend transferring the data. During this time, the radio is powered on and you consume the current specified in product specifications. With similar peak currents, a technology offering higher data rates always spends less power, because it spends less time transmitting and receiving. Conversely, a lower data rate of lower bandwidth technologies generally has better range and coverage, meaning these technologies are able to maintain the link under more difficult conditions (for example, underground parking spaces).
LTE-M is the winner in terms of low latency, so applications that require lower latency than LTE-M should be considered. It is also the preferred choice for moving applications because of the support for mobility. This means that the device has automatic cell handover when it moves, compared to NB-IoT where the device loses connection if it goes out of a cell, and needs to renegotiate with another cell. This can have a high cost of power in the long run.
Besides differences in features and data rate differences, network operators also support different technologies around the world, so you must know which technology is supported in the countries or regions where you plan to deploy the product. Most operators support both, so this is not a major issue. But there are areas, like mainland China, where LTE-M is not supported. See the Mobile IoT Deployment Map for more information.
It may be difficult to decide which parameter is the most important (for example, bandwidth or coverage, mobility/roaming or not). It may not only be different for each product you design but also for each product you ship depending on where it is installed (country, operator used, outdoor, indoor, underground). For mobile (moving) products this may also change depending on the location at a specific time. Therefore, the most popular variant of our nRF9160 SiP is the SICA variant that supports both LTE-M and NB-IoT. When using this variant, the decision is made by your application depending on the environment that your particular product is installed in, or even operate in with real-time switching between the technologies. This means you can effectively use NB-IoT for day-to-day operations, but for Firmware-Over-The-Air (FOTA) updates you switch to LTE-M to get the benefit of the higher data rates.
In most cases we see that LTE-M is the preferred technology if you do not need the high penetration feature and lower bandwidth that NB-IoT offers.