What Is LTE-M and How It Differs From NB-IoT

Choosing how a tracking tag connects isn’t a minor technical detail, it directly determines how long the battery lasts and in which areas it keeps working. LTE-M is one of the two most common cellular options for IoT, and it’s often confused with its sibling NB-IoT without it being clear when each one is the right choice.

What is LTE-M

LTE-M (LTE Cat-M1) is a cellular connectivity technology designed specifically for IoT devices, which takes advantage of the existing 4G LTE network infrastructure instead of requiring new antennas or networks. It belongs to the LPWAN family (low-power wide-area networks), designed to transmit small amounts of data with the lowest possible energy consumption.

Origin and standardization

The technology was formally standardized in 3GPP Release 13 in 2016, as part of a broader effort to adapt mobile networks to the needs of the Internet of Things, which until then had been covered inefficiently with general-purpose 2G or 3G modules that were oversized for what a sensor actually needs. The name “Cat-M1” refers to the LTE device category defined by the standard, a classification that determines the minimum capabilities a chip must support to be considered compatible with the network.

How it takes advantage of the existing 4G network

Its big advantage over building a new network from scratch is that it relies on the same antennas and the same spectrum already used by conventional 4G, the operator only needs to activate support via software on the existing base stations, without rolling out additional physical infrastructure. This explains why LTE-M coverage can expand relatively quickly wherever a good 4G network already exists, unlike technologies that do require new hardware at each site.

How it works

Unlike a conventional LTE connection, LTE-M incorporates power-saving modes that let the device “sleep” between transmissions and wake up only to send data, in exchange for a limited data rate, up to 1 Mbit/s, enough to send position or sensor readings, but not for data-intensive applications.

PSM and eDRX: the power-saving modes

Power Saving Mode (PSM) lets the device enter a low-power state similar to being switched off, keeping its registration on the network but without actively listening for any signal, until it needs to transmit again or until a configured timer expires. eDRX (Extended Discontinuous Reception) works in a complementary way, it lengthens the intervals during which the device “listens” for possible incoming messages from the network, useful when, besides sending data, it also needs to be able to receive occasional commands from the platform, such as forcing an immediate position reading.

Half-duplex transmission

Unlike conventional LTE, which operates in full duplex (transmitting and receiving at the same time), LTE-M usually operates in half duplex, it transmits or receives at any given moment but not both at the same time. This simplifies the design of the radio chip and reduces its cost and consumption, in exchange for slightly higher latency that usually isn’t a problem for the type of data a tracking tag transmits, where an instant response isn’t needed.

Frequency bands and coverage

LTE-M doesn’t use a single frequency band worldwide, each operator deploys it on the LTE bands it already has assigned in each country. In Europe it’s usually deployed on band 20 (800 MHz) and band 3 (1800 MHz), which gives it good indoor penetration thanks to band 20’s low frequency. This means that real LTE-M coverage depends on the operator contracted and not just on the country, two operators in the same market can have very different LTE-M rollouts.

This fragmentation by bands has a practical consequence for anyone manufacturing or buying LTE-M devices, a module designed for the European market doesn’t always work equally well if that same shipment crosses into a market with different bands, such as certain countries in Latin America or Asia. Manufacturers of international tracking tags usually opt for multiband chips, capable of automatically switching between several frequencies depending on the country they’re in, precisely to avoid this problem on journeys that cross borders.

LTE-M vs. NB-IoT

Both technologies are born from the same goal, low-power cellular connectivity for IoT, but they don’t solve the same thing:

When each one makes sense in logistics

For tracking goods in transit, where the device is constantly moving between cells and may need to report its position with a certain frequency, LTE-M is usually the more suitable option. NB-IoT fits better with devices that don’t change location, such as fixed sensors in a warehouse or meters, where all that matters is minimal consumption and penetration into enclosed spaces.

A concrete example helps illustrate this, a pallet traveling by truck from a warehouse in Madrid to a distribution center in Hamburg passes through dozens of different LTE cells along the way, and needs the handover from one cell to the next to happen without noticeable interruptions. That same behavior would be unnecessary, and a waste of power, for a temperature sensor permanently installed in a cold room that never changes location, a case where NB-IoT is the more efficient option.

Other use cases for LTE-M

Although here we’re mainly interested in tracking goods, LTE-M is used in many other contexts with similar needs for low power consumption and mobility:

Wearables and medical devices: portable health monitors that need reliable connectivity without depending on the patient’s phone. Mobile point-of-sale terminals: portable card readers that need a constant connection wherever they move. Smart meters with mobility: less common than NB-IoT in this case, but used when the meter can move or needs a faster response.

Why operators are pushing the migration to LTE-M

Many European operators have announced or already completed the shutdown of their 2G and 3G networks, freeing up that spectrum for more efficient technologies. Millions of M2M devices that have been running on 2G for years, from alarms to meters and vehicle telemetry systems, need an alternative before that shutdown is completed in their country. LTE-M and NB-IoT are the two technologies operators are actively promoting as replacements, which explains why more and more coverage is becoming available and why module costs have come down in recent years, as demand rises and competition between chip manufacturers increases.

Why this choice matters

Connectivity technology isn’t a detail that stays hidden inside the device, it defines how long a tag can last without a battery change and in which geographic areas it keeps emitting data. A tag designed for long journeys with constant movement needs that balance between battery life and the ability to stay connected while it changes cells, changes country, and keeps transmitting its position to the platform without interruptions.

Frequently asked questions

Does a tag with LTE-M need a special SIM?

Yes, but not a traditional physical card in most cases. LTE-M devices usually integrate an eSIM soldered onto the board itself, provisioned at the factory by the manufacturer or the operator, which avoids having to insert or swap physical cards on each tag.

Does LTE-M work in every country?

It depends on the coverage each mobile operator has activated in that country. LTE-M reuses existing LTE infrastructure, but the operator has to have explicitly activated support for LTE-M devices on its network, something worth checking if the goods’ journey is going to cross several countries.

Is LTE-M connectivity more expensive than a normal data SIM?

It’s usually cheaper overall, although it’s not directly comparable. An LTE-M device transmits a very small amount of data, so the specific IoT rate plans for this technology are designed for that minimal consumption, different from a smartphone data plan.

Will LTE-M stop working when 2G or 3G is shut down?

Quite the opposite, LTE-M is one of the technologies designed precisely to replace the M2M devices that today depend on 2G or 3G before operators shut down those networks, so it isn’t affected by that shutdown, it’s their long-term alternative.

What data rate does a tracking tag actually need?

Very little, a few kilobytes per transmission to send GPS coordinates and sensor readings. LTE-M’s maximum speed of 1 Mbit/s is far more than this use case needs, the extra margin mainly helps keep the connection stable while in motion.

Can you switch operators without changing the tag?

It depends on the type of eSIM built into it. Multi-operator profile eSIMs, often through permanent roaming agreements, allow connecting to different networks without replacing hardware, while an eSIM locked to a single operator limits that flexibility.