LTE-M for IoT and M2M: Everything You Need to Know

Eseye

IoT Hardware and Connectivity Specialists

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Of the handful of variants of 4G LTE technology commonly used for IoT and M2M deployments, LTE-M is one of the most well-known and one of the most versatile.

3GPP Release 13 in 2016, known as LTE Advanced Pro, introduced Long Term Evolution for Machines as an M2M specific variant with the simple name LTE-M, but the technology is also known as LTE-MTC (Long Term Evolution for Machine-Type Communication); 3GPP Cat-M1; LTE Cat M1; and LTE eMTC (enhanced Machine-Type Communication).

In this article, which goes into a deep dive of the pros and cons of LTE-M and its use cases, we will use LTE-M for consistency. We have an overview article comparing LTE-M against NB-IoT and LTE Cat-1 here.

LTE-M explained

LTE-M is a member of the LPWA (Low-Power, Wide-Area) family of IoT and M2M technologies, specifically designed for connecting ‘Things’ – machines, sensors, and other devices – to the enterprise network, transmitting data efficiently and reliably, and maintaining a long battery life.

As the name suggests, LTE-M was adapted from the LTE parent standard and shares much of LTE’s architecture and protocols. In terms of deployment, wherever LTE is present, it’s possible LTE-M is available too as LTE-M is just a configuration that needs to be enabled. The technology then operates within the existing LTE network infrastructure.

Although LTE-M has a narrower bandwidth than LTE, it has a longer range, very similar penetration ability to other LPWA technologies, and supports backchannel and SMS for device setup and the updating of eUICC SIMs for profile switching. Along with power saving features and a relatively low cost deployment and maintenance model it is considered ideal for sensors and wearable devices.

LTE-M devices are also very attractive for long-term deployments. Devices can be built around one configuration, shipped, and updated via software and utilize eSIM technology. LTE also has a healthy global ecosystem focused on maintaining the standard for the foreseeable future making LTE-M a solid choice for long term projects.

LTE-M technology breakdown: features and capabilities

LTE-M low power performance

Connected machines were not properly acknowledged until 2016 through 3GPP Release 13. Historically, cellular networks have been designed around consumer and business handset usage, which caters to very different behavior. Cell phones and handsets constantly poll the network to ensure they are connected to the closest or most reliable cell base station and to let the network understand where the user equipment is.

All of this pinging back and forth keeps the device awake and rapidly drains the battery, which is not ideal for IoT. The large screen sizes of modern handsets have been beneficial for manufacturers in that they require a larger form factor and allow for larger batteries in devices. Given that the desired form factor of an IoT device is typically smaller, this has led to some specific considerations for IoT and M2M connectivity technologies in terms of limiting battery draining behavior.

As well as occupying a smaller footprint, IoT devices use battery power more sparingly, perhaps only waking up and sending or receiving small data packets based on a specific trigger, such as a daily check-in, or when an alarm/alert is activated. This means batteries can last much longer. But IoT batteries need to last even longer.

LTE-M introduced two features: Power Saving Mode (PSM), which lets IoT devices go to sleep for extended periods of time; and extended Discontinuous Reception (eDRX), which further extends the timespan for the device waking up and checking for updates via radio.

These features dramatically reduce power consumption, and make it possible for LTE-M IoT devices to have a 10-year battery life on a 5WH (watt-hour) battery.

Radio access

LTE-M uses a modified version of the LTE radio protocols and operates in licensed spectrum bandwidth as low as 1.4 MHz, which is much narrower than the 20 MHz for regular LTE, but is sufficient for the small amount of data transfer needed by IoT devices.

LTE-M has a Maximum Coupling Loss (MCL) of around 156 decibels (dB), which is higher than LTE, and slightly lower than NB-IoT. There are a lot of variables to consider, but this typically means LTE-M networks offer greater coverage and better indoor penetration than LTE, overcoming reflection and absorption interference from buildings and other structures in its path, and is almost on a par with NB-IoT.

MCL is defined as the maximum loss of signal power between two antennas that can still establish a reliable connection, with the power of a radio signal decreasing with distance (free-space loss) as well as reflection, diffraction, and absorption from obstacles. A higher MCL value indicates better signal penetration. Coverage enhancement modes repeat the transmission of data, which ensures data can be reliably transmitted even in difficult-to-reach areas.

When compared to the consumer handset bandwidths of LTE, LTE-M doesn’t seem particularly impressive with around 1Mbps for both uplink and downlink. But this compares very favorably to other LPWANs and for low power IoT use cases is often more than adequate.

Downlink bandwidth for LTE-M is also enough for a device to comfortably receive Over-the-Air (OTA) updates, while consuming less power, meaning the device can update itself and get back to sleep mode quickly.

LTE-M devices often use frequency-division duplex (FDD) or time-division duplex (TDD), which means they can transmit and receive but not at the same time. The setup is largely dependent on variables specific to the deployment, but FDD uses a different swathe of spectrum for uplink and downlink (frequency division), while TDD alternates the spectrum usage based on slices of time (time division).

The decision on which duplexing to use will be dictated by the spectrum available, but in general, the available capabilities reduce the complexity of the radio frequency (RF) front-end and save power.

LTE-M devices also benefit from being able to use a single antenna, making devices less complex than standard LTE units which require Multiple Input Multiple Output (MIMO) antennas. This can reduce design costs. A good quality antenna is still important with LTE-M devices especially in rural areas.

Furthermore, LTE-M can support voice communication using Voice over LTE (VoLTE), which is an important factor to consider for certain IoT applications such as alarm systems or emergency services.

Security

LTE-M is suitable for TCP/TLS end-to-end secure connections, making it compatible with familiar and standard security capabilities as well as network-based authentication.

Mobility and roaming

With LTE-M, full mobility is supported, using the same cell handover features as in regular LTE. But where LTE is designed for high-speed mobility, LTE-M supports lower mobility speeds more suitable for low-speed-mobility IoT devices, which is most IoT applications.

LTE-M is well-designed for a wide range of applications and supports a backchannel as well as SMS for device setup and updating eUICC SIMs, including switching of profiles.

For roaming, wherever LTE is deployed, LTE-M is also a possibility, meaning high support for roaming in regions where LTE is deployed. Full roaming is supported, meaning it is suitable for IoT applications that will operate internationally and across multiple regions.

However, not all carriers with LTE 4G coverage have LTE-M networks, so accessibility may well depend on the regions you intend to target. The GSMA maintains a deployment map for IoT technologies here.

The current map shows that LTE-M is widely deployed within the Americas, Europe, and Australia, while NB-IoT is more prevalent in Russia, APAC, and Saudi Arabia, while Africa, parts of South America, and the Middle East are largely devoid of these IoT networks.

Overall however, the above adaptations make LTE-M attractive for IoT use cases where devices need to send small amounts of data over long periods, in a wide range of environments, while conserving battery life and reducing hardware costs.

LTE-M also benefits from being part of the LTE standard, ensuring good scalability, security, and compatibility with existing cellular network infrastructure.

Limitations of LTE-M

The main consideration that applies to all IoT and M2M deployments is the use case, followed closely by the region(s) the application is to be deployed in. Answering these two questions will help narrow down the options in terms of connectivity and in some cases may even eliminate all but one technology.

The intended device or deployment may well dictate the best connectivity solution, based on bandwidth constraints, where LTE-M may be inadequate for high data rate applications or high-speed data transfer needs.

LTE-M may not be available in certain countries, as shown on the map above.

LTE-M IoT use cases

With a latency of just 10-15 milliseconds and its ability to support handovers and mobility, LTE-M is an excellent choice for IoT applications that need to be mobile, such as asset tracking, fleet management devices, and wearables.

Asset tracking, shipping and logistics

LTE-M has long-range coverage, handover, roaming, and low power consumption making it ideal for real-time tracking and monitoring of assets without frequent battery replacements. It’s suitable for tracking assets by road, rail, or sea (even air if you consider that tracking can resume at the destination) and has some penetration into buildings.

This makes it suitable for shipping containers, pallets, fleet vehicles, machinery and equipment, and even human (or animal) worn devices.

Agriculture

As well as applications for tracking and securing farm vehicles and machinery, LTE-M is useful for cost-effective monitoring of crops and soil conditions.

Farming applications include the remote monitoring and control of irrigation systems, environmental sensors for weather, and other real-time alerts about equipment malfunctions.

Remote monitoring, sensors, alarms

LTE-M’s high reliability, wide-range coverage, and in-building penetration makes it suitable for monitoring essential infrastructure, such as utilities, pipelines for the energy or water sector, and other industrial applications.

Healthcare

LTE-M’s low power consumption and long battery life, coupled with its coverage, mobility, and reliable connectivity, makes it ideal for IoT healthcare applications in telecare and telehealth.

Real-time transmission of critical health data and remote monitoring are possibilities, allowing delivery of personalized healthcare.

Wearable devices

While wearable devices from smartwatches and fitness trackers to augmented reality headsets are becoming more and more common in our daily lives, IoT wearables have a range of applications in the enterprise sector.

Use cases include environmental and biometric sensors that measure environmental factors, like temperature and air quality, or body temperature and stress levels. Other augmentation devices could provide real-time updates or instructions, including data visualization for workers in manufacturing, healthcare, and logistics, or other services such as geofencing and location-sharing.

Smart cities

LTE-M is suitable for a wide range of applications in the smart city sector both publicly and privately. This includes IoT-based building management and monitoring, vending machines, essential infrastructure control and a whole host of safety, security, and convenience features for cities. 

Is LTE-M right for my IoT deployment?

LTE-M is designed for low-power applications requiring medium throughput – so more than NB-IoT. It has a narrower bandwidth than LTE, but it does give you a longer range, although with less throughput. 

In its favor, LTE-M has more roaming networks available than other technologies, and it supports and future-proofs more use cases, with a configuration that lends itself to power saving and better cost saving for large-scale deployments. Ultimately however, the decision to use LTE-M will be dictated by the IoT or M2M application or use case.

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Eseye

IoT Hardware and Connectivity Specialists

LinkedIn

Eseye brings decades of end-to-end expertise to integrate and optimise IoT connectivity delivering near 100% uptime. From idea to implementation and beyond, we deliver lasting value from IoT. Nobody does IoT better.

In this article

• LTE-M explained
• Technology breakdown
• Use cases
• Is LTE-M right for your project?