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.
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:
Why don't we use existing 3GPP technologies such as 3G or 4G for IoT applications? There are a number of reasons, e.g.
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.
Here are the LTE Cat bands and their technical specifications from Wikipedia. There are different 3GPP standard releases, and Release 13 yielded the standardization of LTE Cat M1, Cat NB1 and EC-GSM-IoT.
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.
To summarise: NB-IoT,
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.