Narrowband IoT: Choosing a module according to project requirements

In our last blogpost, we laid out the foundation of Narrowband IoT knowledge, what it's about and what kind of IoT projects it might be used for.
NB-IoT is a new way of communication for the "things" which use the subsets of LTE standard, and which carry small volume of data transmission over long periods. Narrowband offers both low power consumption and low cost hardware expenses.

Now for a prototyping project, a typical question is exactly what module to buy because there are quite a few to choose from. In the past few weeks we've been working intensively with chips from Quectel, and we're happy to share our insights!

Today we will explain the points for considering the best module for your IoT projects. Please note that only chips from Quectel will be examined today.

We'll have a look at the following topics:

  • Coverage Regions: Where on this planet can you deploy your solution?
  • Frequency Bands: What bands are used für LTE M/NB, and which are supported by providers and regions:
  • Certifications: Primarily what telco operators are supported by the module?
  • Compatibility: What kind of chips work together?
  • Data Transmission: Which transmission standards do the modules support?
  • Data Stacks and Protocols: Looking the at the ISO/OSI layers, what is supported here?
  • IO and Update Interfaces: What (additional) I/O interfaces do the module support?

Quectel offers several modules which other vendors use to build their development boards (that's what we're testing, as IoT prototyping webdevs). Essentially, the module base names are BC95, BC66, BC68 and BC96.

Let's start by looking at where you can deploy which modules.

Coverage Regions:

The very first thing that you need to consider is of course choosing the chip according to your geographical location. Different chips support communication in different countries. Note that there are four different models of BC-95 and the sub-models support different regions. Some chips can be also used globally, because they support multiple frequency bands. Some modules are single-band only (primarily the BC95-Bxx), so their application is limited: e.g. BC95-B5 can only be used in China/Korea and BC95-B28 can only be used in Australia.

Image 1

Frequency Bands:

Different chips support different frequencies for communication. For desired frequency, you can select the best option for you. i.e. BC66 is leading the amount of supported frequencies.
Different bands support different uplink and downlink frequencies. i.e. B12 and B13 looks like they are operating in 700 mHz band but they use different bandwidth for uplink and downlink. Additionally, some bands are "non-Narrowband" bands, and are being used for GSM-communication in older networks (i.e. as a fallback option).

Image 2

Certifications:

Certifications vary from different service providers. On the following table, the global certifications can be observed. According to be certified in a given provider, the chip should be selected carefully. Here the BC96 supports the greatest amount of certifications, as this module is supposed to be Quectels flagship. Certifications are mainly important when it comes to SIM card selection, so make sure your module choice fits your operator choice.

Image 3

Compatibility:

Compatibility plays an important role during implementations with other chips together. BC96 supports all the chips that are given in the list. According to your current system, the chip you select should be compatible with the running system, which is mainly a question from a usage perspective (e.g. wether you need UMTS/HSPA fallback or not)

Image 4

Data Transmission:

If additional communication protocols are important for your project, you can select your chip according to data transmission protocols they support.

  • BC95 does not support multi-tone data transfer.
  • Edge, GPRS and Cat M1 is only supported by BC96.
  • Voice transmission is also only supported by BC96.
  • Except P2P and MT SMS transmissions, all the methods are supported by these chips.

Image 5

IO and Update Interfaces:

For the most part, the IO interfaces are supported by every chip. The exception to this is PCM, GPIO, Netlight and USB, which are only supported by BC96. i.e. USB interface is only supported by BC96. Update interfaces are also important if you need to update with USB or weather location services via GNSS are important for your use case.

Image 6

Data Stacks and Protocols:

Supported data stacks can be seen on the following table. The popular IoT communication protocols as MQTT, CoAP, UDP, TCP/IP and HTTP are worth considering. This table is interesting, especially regarding the lower half containing higher-level protocols (e.g. HTTP). Some module carry this all on-chip, but it makes only sense in applications where TCP can be used (because HTTP runs over TCP), e.g. in a UMTS fallback scenario. Narrowband IoT, LTE Cat NB - with its latency - makes heavy use of UDP, and higher level TCP-based protocols simply do not make much sense here.

Image 7

Summary:

Today we discussed on vitally important pre-steps in order to choose the right NB-IoT chips for your IoT project. NB-IoT can be a big step forward not only for smart city projects and car-bike sharing, but also indoor/outdoor smart systems and so on. It is always better to discuss possible locations for your IoT project for deciding on coverage. After that, the desired frequency band for communication, -uplink and downlink- should be selected. Supported protocols are also important when it comes to voice-sms-data transmission and data stack protocols.

The next steps will be about certification, in order to guarantee the compatibility of SIM cards. Different providers have varying certifications, so it is better to check certification from carrier side. If you have a running system and want to implement new chips for NB-IoT, you need to care about compatibility with other Quectel chips. Lastly, the interfaces for update and IO need to be checked.

That's all! You are now in a pretty good shape before ordering the best chip for your project!

In our upcoming blog posts, we’ll be telling you all more about NB-IoT technologies, use cases and programming for NB-IoT.

Eren

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