Every IoT device needs a way to communicate to establish (usually wireless) connections. Even though the most obvious choice might seem to be using WiFi to connect with an available router, actually various technologies can be used for that purpose, each of them having its pros and cons. This decision is highly dependent on power-usage requirements, the range and coverage needed. In this article, we would like to present the basics of NB-IoT communication, the configuration of the example NB-IoT module, and setting up a connection to the MQTT broker.
If we were to try to gather and compare various wireless communication technologies, we could present them on a figure like the one below from [1]:
This figure compares different wireless technologies in terms of range and bandwidth. As pointed out by the author in [2], even though at first sight it might seem that the technologies from the top right corner are better than the other, actually it is not true. In some cases, short range might be acceptable (or even desirable for security reasons). Apart from this, this figure does not include one important variable – power consumption. In NFC the passive device basically does not need an internal power source at all, while WiFi may need such a high power consumption that can drastically decrease the usage time for a battery-powered device.
Narrow Band Internet of Things (NB-IoT) is a low-power wide area network (LPWAN) radio technology developed by 3GPP. It uses a subset of the LTE standard but limits the bandwidth to a single 200 kHz band. It is targeted for applications that require low power consumption, good indoor coverage, and that don’t require a high data rate.
LTE M or LTE-MTC (Long Term Evolution Machine Type Communication) is another low-power wide area network (LPWAN) radio technology developed by 3GPP. Compared to NB-IoT it offers a higher data rate, and mobility (handover is possible) but at the same time is more expensive and requires more bandwidth. In general, it has a little worse indoor coverage than NB-IoT.
NB-IoT would be a good choice for static devices (that will not need to switch between different base stations) with low data rates for which cost is an important factor.
LTE-M will be a better choice for a mobile device that needs to send higher amounts of data and for which higher costs of the components will not be a problem.
In order to start working with NB-IoT you need to select the connectivity provider. There are various options available – e.g. iotcreators.com, 1nce or onomondo. An important issue in this case is coverage. You need to make sure that the selected provider guarantees coverage in the location in which you plan to use or test your device and if your use case fits the requirements of the given provider.
Coverage for NB-IoT and LTE-M seems to be much different at this point, compare the coverage maps from 1nce, IoT Creators and onomondo (state on the 27h of June, 2024):
WizzDev is a company from Poland – in our case, the only option to test NB-IoT would be to use a SIM card from IoT Creators – other operators either don’t offer coverage for Poland or require usage on a much larger scale than testing and development purposes.
As you can see on the above maps, in many cases, coverage for NB-IoT and LTE-M is mutually exclusive – many countries have access to only one of those technologies. Is there an easy way to make this flexible from the device’s point of view? As it turns out, there is.
Some modules (e.g. SIM7080G) offer to establish a connection using either NB-IoT or LTE-M. Depending on the country of origin, you may need different SIM cards for both of these cases (if your operator does not support both methods in the given region), but with proper configuration, the device using this module could be configured to use either of these connectivity methods.
Another important piece of information to check is your operator ID and the deployment bands that it uses. Such information for the IoT Creators is available here. It is important to make sure that your module supports at least some of the deployment bands used by your operator (for example – SIM7020C is intended for the China region and may not support deployment bands available in Europe).
Summary
In this article, we have briefly described the NB-IoT and LTE-M technologies, their applications and possible challenges that might appear when trying to implement this in your solution. If you think that we have not even barely touched the surface of the complexity of this problem – you are right! That is why we are not stopping here and next time we will describe how to connect and communicate with two Waveshare modules SIM7020E and SIM7080G using a USB-UART converter. Stay tuned for our next article!
References:
- S. Montagny – LoRa – LoRaWAN and Internet of Things for beginners
- S. Montagny, A. Augagneur – LoRa and LoRaWAN for Internet of Things (udemy course)
- https://en.wikipedia.org/wiki/Narrowband_IoT
- https://en.wikipedia.org/wiki/LTE-M
- M. Bosson – NB-IoT vs LTE-M: Comparing the two IoT technologies (onomondo.com)