What is series (#8): what is LTE-M (Long Term Evolution for Machines)?

LTE-M, short for Long Term Evolution for Machines or LTE-MTC, is a low power wide area network radio technology standard for Internet of Things (IoT) applications.

It is one of the three LPWA network technologies of the cellular/mobile industry which were standardized by 3GPP (3rd Generation Partnership Project). The other two standards are NB-IoT and EC-GSM-IoT. I started my overview of cellular LPWAN technologies with NB-IoT since this standard is most direct answer of the mobile industry to non-cellular LPWAN technologies such as Sigfox, LoRaWAN and Ingenu. Moreover, NB-IoT was first rolled out in Europe and US mobile network operators who deployed LTE-M before are now launching their NB-IoT networks.

LTE-M is also often called eMTC, short for enhanced machine-type communication: both terms are used interchangeably. The specifications of LTE-M (and the two others) were published in 3GPP release 13.

Main characteristics of LTE-M

What is LTE-M, how does it differ from NB-IoT and what are the main features and some typical use cases?

In case low power wide area network technologies are still relatively new I invite you to first read my post on LPWAN. Within the landscape of LPWA technologies, LTE-M (and the others) have their specific places. In my IoT book ‘Digitize or Die‘ I also explain how LTE-M/eMTC, NB-IoT and EC-GSM-IoT, are evolutions of existing mobile/cellular technologies for cellular network operators to leverage their existing geographic base stations’ footprint, private radio spectrum and market access.

Here are the main characteristics of LTE-M/eMTC:

• LTE-M is a more powerful technology than NB-IoT. LTE-M allows the reuse of the existing LTE installed base of operators. It can be deployed within an LTE band and is in fact a stripped-down version of LTE, offering a simplified design with 1.4 MHz bandwidth. As a reminder: NB-IoT was designed for a narrow band of 200 KHz and can be deployed in three different ways.
• The data transfer of LTE-M can go up to 1 Mbps in both directions (uplink and downlink) with actual throughput depending on the way it is used (e.g. full-duplex), the operator’s technology and the local situation. LTE-M has the highest bandwidth and throughput of all LPWAN options.
• Latency of LTE-M is very low with delays of 10 to 15 milliseconds (NB-IoT is 1.6 to 10 seconds), making it fit for full-duplex real-time use cases.
• Battery life of devices is extended through the sleep mode or power saving mode (PSM) and through extended discontinuous reception (LTE eDRX).
• Just like NB-IoT, LTE-M also has a deeper penetration in buildings than LTE networks. LTE-M has a link budget of 155.7 dB.

LTE-M further supports voice (VoLTE) and mobility. Voice can be handy in some use cases (attention: do check if the operator you work with has it turned on) while the good support of mobility makes LTE-M the better choice in cellular LPWAN for use cases with moving ‘things’.

LTE-M use cases

This brings me to the use cases for LTE-M. Although there are other LPWAN technologies that can be a good fit for some of these use cases and there are always overlaps – depending on your region and what your application precisely needs – typical LTE-M use cases include applications with non-stationary devices, use cases needing a real-time communication and use cases where higher data transfer speeds and volumes are needed.

Previously I mentioned that the fastest growing use categories that drive the LPWAN market are smart metering and asset tracking. The latter provides ample opportunities for LTE-M across use cases involving these non-stationary assets. Other examples of LTE-M use case categories include wearables, healthcare devices, smart grid, applications in logistics/transportation, city infrastructure, telematics and more.

The image from an infographic (download in PDF here) by Sierra Wireless below gives a good overview of the main differences between LTE-M (release 13) and NB-IoT with more typical applications per technology whereby speed and latency are two parameters.

The future of LTE-M: hand in hand with NB-IoT

As already mentioned in my article on NB-IoT the networks offering one or more cellular LPWAN standards are certainly not omnipresent yet. However, in 2019 announcements from mobile network operators keep coming at a fast pace.

The fact that both NB-IoT and LTE-M fit in the roadmap to 5G might also play a role in this, on top of the grown awareness that both cellular technologies are complementary. Most new LTE-M network announcements come from the regions, such as Europe, where NB-IoT was the first choice, while in the US it’s precisely the opposite. Still, according to the chart below there are less LTE-M networks for the time being. The image at the top of this post – which gets updated regularly by the GSMA – shows in which countries LTE-M, NB-IoT and both networks are available.

Recently I conducted an interview with the CEO of an IoT startup that works a lot with mobile network operators in Europe on the evolutions in vehicle tracking and cars which I’ll publish shortly. In another interview he says that in Europe operators who already offer NB-IoT “slowly move from narrowband-IoT towards LTE-M” with both likely to co-exist since they indeed serve different needs.

This is also confirmed by analysts who closely follow the cellular market closely. They all expect that the growth of licensed cellular LPWAN connections with LTE-M and NB-IoT will be much higher than that of any other cellular connectivity method, including 5G cellular IoT, throughout the first half of the next decade.

In a next post I will cover the final low power wide area standard in my series, EC-GSM-IoT, and compare all the different LPWAN technologies.