LTE, LTE-M, LTE-cat1bis, NB-IoT: a few pointers to find your way
Four technologies that share the same LTE acronym but have little in common — two of them designed for low-power connected products. Our field view, no sugar-coating.
The problem with the LTE family
When people talk about LTE for connected products, they often mix up very different things. Standard LTE is the 4G in your smartphone. LTE-M, NB-IoT and LTE-cat1bis are variants designed for devices — with very different trade-offs on data rate, power consumption, coverage and complexity.
What you are reading here is our field view. Not a catalogue of datasheets. We have opinions, based on design and integration experience — and we share them frankly.
Honestly compared
Same acronym, radically different philosophies. Here is our unfiltered analysis.
Designed for mobile broadband. Excellent for watching videos, not suited to connected products. Data rate too high (pointless), power consumption too high, SIM cost too high. If your design office proposes standard LTE for a sensor, run.
A data rate of 1 Mbit/s — enough for modern OTA mechanisms and CRA-compliant cryptographic protocols. That is its real strength.
Its reputation is mixed, and that is understandable. Many design offices have had bad experiences with LTE-M… because they used it badly. PSM (Power Saving Mode) and eDRX (Extended Discontinuous Reception) are the mechanisms that let the modem truly sleep. Those who simply "brutally cut" their LTE-M modem when they no longer needed it got a nasty surprise: on wake-up, the modem has to reconnect to the network and re-exchange encryption keys before sending its frame. Result: disappointing power consumption, and disappointed teams.
Used correctly — with properly configured PSM/eDRX — LTE-M reaches outstanding power-consumption performance. It is a technology that demands a careful implementation, but rewards those who master it.
100 kbps data rate. In theory slightly better range and penetration than LTE-M — in practice, the difference is rarely significant. Power consumption similar to LTE-M with PSM.
Its main problem: 100 kbps is too slow for serious OTA with modern cryptographic mechanisms. This makes it hard to reconcile with new regulations, notably the CRA. Little deployed in Europe compared with LTE-M.
Our bet: NB-IoT will quickly be superseded by LTE-M or LTE-cat1bis. That is our opinion, not a certainty — but we would not invest in it for new projects.
The story of LTE-cat1bis is an interesting one. When the big chipset manufacturers saw that IoT on LTE bands was going to take off, they sought to leverage their existing radio infrastructure (same frontend as standard LTE) rather than invest in a dedicated LTE-M frontend.
The result: a technology that works wherever an LTE phone gets a signal. No need to check LTE-M coverage — if you have 4G, you have LTE-cat1bis.
The first implementations performed "as well as an LTE-M modem yanked out of its socket"... which was the bar to beat. Since then, the chips have been optimised. Today: up to 10 Mbit/s, power consumption on a par with LTE-M — with properly implemented PSM/eDRX. You can do serious IP with advanced cryptographic systems on low-power devices.
At Codium: our LTE-M building block is proven and very efficient. Our LTE-cat1bis building block is under development.
The 4 technologies side by side
A quick summary to decide without drowning in datasheets.
| Criterion | Standard LTE | LTE-M (Cat-M1) | NB-IoT | LTE-cat1bis |
|---|---|---|---|---|
| Downlink data rate | 150 Mbit/s | 1 Mbit/s | 100 kbps | up to 10 Mbit/s |
| Power consumption (PSM/eDRX) | Very high | Excellent | Good | Good (if well implemented) |
| Coverage in France | Nationwide | Dedicated LTE-M | Limited | Wherever 4G reaches |
| CRA / OTA compatibility | No (cost) | Yes | Difficult | Yes |
| Typical use case | Smartphone, tablet | IoT sensors, trackers, wearables, predictive maintenance | Simple low-data-rate meters (existing projects) | Low-power IoT where wide coverage is required |
| Codium recommendation | Avoid for IoT | Main choice | Existing projects only | Promising, under development at Codium |
The right technology is good. A good antenna is essential.
Choosing LTE-M or LTE-cat1bis is pointless without a properly sized and qualified antenna. Our RF specialist designs and measures your antennas in-house.
FAQ — LTE-M, NB-IoT, LTE-cat1bis
What is the difference between LTE-M and LTE-cat1bis?
The key difference is in the radio frontend. LTE-M uses a dedicated frontend, different from standard LTE — which gives it an advantage in penetration and range in difficult environments, but means you must check LTE-M coverage with your operator. LTE-cat1bis reuses the same frontend as standard LTE: it therefore works wherever 4G reaches, with no additional checks. In return, range and penetration are slightly lower. Both technologies are CRA-compatible and allow serious OTA. At Codium, our LTE-M building block is proven; our LTE-cat1bis building block is under development.
Is NB-IoT compliant with the Cyber Resilience Act?
It is difficult, and that is one of its major problems. The CRA requires security updates (OTA) throughout the product's lifetime. With 100 kbps on NB-IoT, transferring a signed firmware with modern cryptographic mechanisms becomes either very slow or technically impossible, depending on the firmware size. LTE-M at 1 Mbit/s — and all the more so LTE-cat1bis at 10 Mbit/s — do not have this problem. This is one of the reasons we advise against NB-IoT for new projects.
How does Codium implement LTE-M PSM/eDRX?
This is precisely what makes the difference between a good LTE-M project and a bad one. We do not "cut" the modem: we correctly configure the PSM timers (T3324/T3412) and eDRX so that the modem sleeps without losing its network context. On wake-up, the device can send its frame immediately, with no reconnection sequence or key re-exchange. Result: power consumption that lives up to the promises of the technology. We validate this implementation with µA-level current measurements on the final hardware, under real conditions (Orange, SFR, Bouygues).
Is an operator subscription required for LTE-M?
Yes. Both LTE-M and LTE-cat1bis use the operators' infrastructure (Orange, SFR, Bouygues). A dedicated IoT data subscription costs around €1 to €5 per board per year for significant volumes. Multi-operator eSIM solutions exist to optimise coverage, notably in rural areas or internationally.