This blog post gives an overview of NB-IoT technology and its specifications, as well as a discussion of the reasons for choosing NB-Iot instead of current protocols. This post will give you some additional knowledge about NB-IoT applications, hardware selection, shields and programming it for NB-IoT.

Let's Start!

NB-IoT, also known as LTE Cat NB1, is a LPWAN technology standard developed by 3GPP. Simply, 3GPP is a collaboration of telecommunication standards associations. The first duty of 3GPP was to make 3G technology based on GSM, after which this scope is expanded to 3G, 4G, LTE etc. technologies. NB-IoT can co-exist with 2G-3G-4G mobile networks. There are several LPWAN technologies around, and we've already been looking at some of them, e.g. LoRaWAN and SigFox. So let's try a short comparison.

First, here are some basic differences between LoRaWAN, SigFox and Narrowband communication protocols:

• NB-IoT has a faster response time, and telco operators are expected to provide a coverage better than the others (at a cost, though, and with different roll-out levels for different countries)
• LoRa consumes less power than NB-IoT and better for single-building applications, but it has longer latency and lower data rates
• SigFox supports wide area of coverage but mobility is difficult and it can send small data packages very slow

Why don't we use existing 3GPP technologies such as 3G or 4G for IoT applications? There are a number of reasons, e.g.

• High power consumption: IoT devices should live on battery of extended periods of time without service
• Low indoor penetration: Some use cases require installations in factories or within building basements
• Expensive data volume plans: IoT sensor networks typically require much less data traffic, but have to be cost-efficient
• Complex deployment on existing systems

NB-IoT is a new way of communication of the “things” which use the subsets of LTE standard, and which carries small volume of data transmission over long periods. Mathematically, bandwidth is the difference between the upper and lower frequencies of the signal. For NB-IoT, the bandwidth of LTE is limited to single narrowband of 200 kHz and thanks to that, the power consumption is decreased. This unused 200 kHz band have previously been used for GSM or CDMA communications.

There’s a lot of technical detail in here, but we'd like to highlight some values in particular.

First, data rates sound interesting. The data rate for Cat NB1 is lower than for other LTE standards, and this plays well together with IoT devices being used within sensor networks, where data points are to be transmitted frequently but typically use much smaller payloads. There are of course exceptions here, such as Industrial IoT machine telemetry. Depending on using Multi Tone or Single Tone, Download/Uplink Rates are asymmetric. This makes it perfect for sending small amounts and receiving larger (or medium-sized) amounts such as firmware upgrades.

Even more interesting to us is the latency involved. From LTE in our smart phones we're used to small latencies, and the availability of the full range of TCP/IP services. Now for Cat NB1, the latency is significantly higher (1.6 secs, up to 10 secs). This can have a huge impact on the selection of higher-layer protocols. With the TCP connection setup being a three-way handshake (SYN → SYNACK → ACK), this would a significant impediment for using web protocols. NB modules therefore typically focus on providing UDP and CoAP (which is over UDP) as protocols.

Summary on Narrowband-IoT

To summarise: NB-IoT,

• has industry based standards and applicable for many professional applications
• is resource efficient
• is a low cost communication type.
• is optimised for very low battery consumption.
• serves extended long range coverage and high connection density.
• has deeper penetration for better communication deep-indoor, underground and rural areas than LTE M1.
• has +20dB stronger indoor coverage than GSM.
• has wider and easier deployment into cellular systems.
• has high network security and reliability.
• has lower component costs.

Conclusion

If you want to go into the NB-IoT domain for your IoT application, you should check the coverage first because this can differ quite a bit between countries. According to your geographical location, you can select a network. Next, you can select your hardware or shield. Different models of chips support different bands in different countries. This should be also selected according to your location and desired frequency band. In the end, you should look at carriers and their billing method. Some vendors (e.g. here in Germany) are offering SIMs with a 10y lifetime. Some of the operators may provide different services on their clouds regarding data processing or similar.

Additional References

• https://www.link-labs.com/blog/overview-of-narrowband-iot
• https://www.link-labs.com/blog/nb-iot-vs-lora-vs-sigfox
• https://de.slideshare.net/M2M_Alliance/nbiot-pros-and-cons-of-the-new-lpwa-radio-technology

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