So you have finally decided to create a 4G (LTE) variant of your 2G (GSM) device? But are overwhelmed by the number of options available for LTE modules? This guide will perhaps help you decide.
Let’s look at the major things to consider when selecting an LTE module:
LTE operates in bands, and each country/ region supports only some specific bands. In fact, this is not only dependent on your region, but also your service provider. Consider India. It has 3 major cellular network providers: Vodafone + Idea (or VI after the recent rebranding), Airtel, and Jio.
Now, VI uses the LTE bands 1, 3 and 40 for providing 4G services. Airtel uses the bands 3, 8 and 40, while Jio uses the bands 5 and 40. Thus, if you are building a device for India, you will be best served by a module which supports the bands 1, 3, 5, 8 and 40.
Similarly, different countries/ regions will have different requirements. Europe, for instance, is dominated by bands 3, 7 and 20. The Americas are dominated by bands 4, 12 and 66.
You can get the list of supported bands by region and operator here.
The next thing to consider is the category. Simply put, category represents the level of evolution of your LTE service. Higher the category, higher the downlink and uplink speeds and higher the bandwidth. On the flip side, higher category also corresponds to higher power consumption and higher cost of the module
To give you a perspective, LTE Cat 1 has a downlink speed of 10 Mb/s and an uplink speed of 5 Mb/s. In comparison, LTE Cat 14 has a downlink speed of 3917 Mb/s and and uplink speed of 9585 Mb/s. You can get information on other LTE bands here.
For most IoT applications, you might have figured out looking at the numbers above that even LTE Cat 1 is overkill. Further, power consumption and cost are major concerns for IoT devices. People realized that and therefore LTE Cat M1 (LTE-M) and NarrowBand IoT (NB-IoT) were introduced.
LTE Cat M1 is a toned-down version of LTE Cat1 while NB-IoT is a toned-down version of LTE Cat M1, with specs suited for IoT devices. To give you a perspective, LTE Cat 1 has a bandwidth of 20 MHz, LTE Cat M1 has a bandwidth of 1.4 MHz, while NB-IoT has a bandwidth of 180 kHz. Other features (uplink and downlink speeds, power consumption, cost, etc. are similarly scaled). A detailed comparison is given here.
Please note that if you are feeling grateful for the existence of LTE-Cat M1 and NB-IoT, then hold on. You need to make sure that your country supports these bands. For instance, LTE-Cat M1 is not supported in India as of 2021. NB-IoT is still in the pilot phase in many cities across India, and AFAIK, not commercialized.
You can get the latest status of whether your country supports LTE-M and/or NB-IoT here.
Also, given the small bandwidth of NB-IoT, it simply can’t work in applications like real-time asset tracking. It may be suitable for low-bandwidth projects like home automation system, or smart city devices. For higher bandwidth applications, LTE-M or LTE Cat 1 may be more suitable. You may decide through experiments if aren’t sure if the specs of NB-IoT and/or LTE M will suit your application.
3. Fallback to 2G/3G
You need to be very careful about this feature. This may be your only savior in difficult terrains. For instance, if you are planning to deploy your devices in rural areas in developing countries, where 4G has not penetrated fully, you may need 2G/ 3G fallback for your devices to keep working.
Also, you will need to check if your operator supports 2G/3G fallback. In India, for instance, Airtel and Vodafone support 2G/3G fallback, but Jio doesn’t.
Whether the module supports 2G/3G fallback is generally mentioned in the specs sheet of the module.
It is quite possible that you are migrating your 2G hardware to 4G. If that is indeed the case, it will be a good idea to check if there is a module available whose hardware footprint matches your 2G module’s footprint exactly. That will facilitate faster prototyping and save redesigning efforts. Several chipmakers are trying to ensure compatibility between their 2G and 4G module’s footprints.
5. GNSS Support
If you are building an asset tracking device, then you may want to check if the module has GNSS support. That will save you the trouble of searching for a separate GNSS module. You may also want to check which constellations are supported.
For instance, SIM7600E by SIMCOM supports GPS, while SIM7800E supports GPS, Beidou, GLONASS, as well as Galileo.
Finally, if you may want to check if the devices comply with the local regulations. If you plan to ship your devices internationally, then you may also want to check compliance with the target market regulations. Most chips will have GCF/ ROHS/ CE/ FCC certifications. Some chips are also certified by network operators. For instance, u-blox’s LARA-R202 chip is certified by AT&T and T-Mobile. This would give you further confidence if you are planning to use this chip with SIM Cards of these operators.
I hope this article would have helped you in your device selection journey. Any other factors to consider that I’ve missed out on? Let me know in the comments below. You can also check out other posts related to cellular modules and firmware over here.