NB-IoT vs LTE-M vs Cat-1 bis vs Cat-4
The Cat number is not a rank. Payload, interval, mobility and destination bands decide the bearer. Compare the trade-offs before the module choice.
NB-IoT, LTE-M, Cat-1 bis and Cat-4 are four cellular bearers with different trade-offs in payload, power, mobility and reach. The category number describes peak capability, not fitness. Choose from what the device sends, how often, whether it moves and which bands the destination operators run.
Key facts
- Cat-4 carries up to 150 Mbps down and 50 Mbps up. Cat-1 bis carries 10 Mbps down and 5 Mbps up.
- NB-IoT uses a 180 kHz channel; LTE-M uses 1.4 MHz inside the LTE grid.
- NB-IoT is built for fixed devices; LTE-M, Cat-1 bis and Cat-4 support mobility.
- Power saving comes from PSM and eDRX plus the radio; the bearer alone does not set battery life.
On this page
The Cat number is not a rank
Cat-4 is not better than Cat-1 bis, and Cat-1 bis is not better than LTE-M. Each label describes a different balance of throughput, power, mobility and reach. A water meter and a camera both need cellular data, but they need opposite things from the radio. Choosing the highest number buys power drain and module size the device may not need.
Start from the traffic and the physical installation, not from a category. A device that sends 40 bytes once a day from a basement has a different profile from one that uploads a photo on motion. The first can sleep for days and needs deep reach. The second needs uplink capacity and a network that handles cell changes.
The four bearers side by side
| Item | NB-IoT | LTE-M | Cat-1 bis | Cat-4 |
|---|---|---|---|---|
| Payload | Small and infrequent | Small to moderate | Positions, logs, small images | Images, audio, bulk logs |
| Send interval | Minutes to days | Seconds to hours | Seconds to minutes | Continuous or bursty |
| Mobility | Fixed; no handover | Cell changes supported | Cell changes supported | Cell changes supported |
| Power | Lowest draw | Low draw | Moderate draw | Highest draw |
| Coverage | Deepest indoor reach | Extended LTE coverage | LTE coverage | LTE coverage |
| Peak rate (UE category, theoretical) | tens of kbps (Cat-NB1 ~26/66 kbps; Cat-NB2 ~127/159 kbps peak) | ~1 Mbps peak (Cat-M1) | 10 Mbps down / 5 Mbps up peak | 150 Mbps down / 50 Mbps up peak |
| Channel | 180 kHz | 1.4 MHz | LTE carrier | LTE carrier |
| Voice | No | Optional VoLTE | VoLTE where offered and the module supports it | VoLTE where offered |
Peak rates come from the UE category; the deployed rate depends on the operator, the band and the signal.
Choose from the traffic profile
Write down five answers before you compare modules: payload size, send frequency, whether the device moves, the power source and the required service life. A meter that sends a 40-byte reading once a day, indoors, on a ten-year battery points to NB-IoT or LTE-M. A tracker that reports every 30 seconds while moving points to LTE-M, Cat-1 bis or Cat-4. A camera that uploads a JPEG on motion points to Cat-4.
Then add the constraints a datasheet hides: the bands the module supports in each destination, whether the operator has certified that module, whether roaming is allowed and how long a power-saving sleep the application can tolerate. The band finder checks the radio side, and the EARFCN tool translates a channel number into a band. If the profile sits near a boundary, prototype on the lower-power bearer first and measure the power draw in the real enclosure.
A module does not cover every band a network uses
| Band | Relative reach | What it means |
|---|---|---|
| B28 | Yes | Network uses |
| B3 | Yes | Network uses |
| B7 | Yes | Network uses |
| B41 | No | Network uses |
| n78 | No | Network uses |
Text description
The example module supports the 700, 1800 and 2600 MHz bands and does not support the 2500 MHz or 3500 MHz bands. A destination operator may use any of them. Band support is a property of the module and the antenna design, not of the bearer label, so check the variant you will ship.
What the throughput label hides
The category is a peak-rate label negotiated between the device and the network. Cat-4's 150 Mbps assumes a wide channel, good signal and a clear network. A camera behind a wall will see less. Cat-1 bis at 10 Mbps down is still far more than a position report needs, and its single receive antenna reduces component count and power. NB-IoT and LTE-M trade rate for reach and battery; their value is that the radio can sleep for long periods and still be reachable.
Check the uplink as carefully as the downlink. Firmware updates, log uploads and images run in that direction, and a device that looks fast on paper can stall on a 5 Mbps uplink. Bandwidth is a separate constraint from peak rate: NB-IoT fits in a 180 kHz block, LTE-M needs 1.4 MHz, and the LTE categories use ordinary carriers. A multi-mode module can fall back, but only if the operator runs the fallback network and certified the module for it.
Power saving and coverage
Battery life comes from network features, not only the radio. Power Saving Mode lets a device sleep for hours or days and wake with its context retained. Extended discontinuous reception stretches the paging cycle so the receiver wakes less often. Both are negotiated with the network and must be supported by the module and the operator. A long sleep saves power but adds wake-up latency, which matters if the application needs a response on demand.
Coverage works the other way. NB-IoT has the largest link budget of the four, which is why it reaches basement meters and sealed sensors. LTE-M adds coverage enhancement but less than NB-IoT. A link budget on paper does not survive a metal cabinet, so test the real enclosure, antenna and mounting position. If the device must be reachable at any moment, measure the wake-up path, not only the sleep current.
Network life and roaming
Choose a bearer the destination operators actually run. LTE-M and NB-IoT deployments differ by operator and by market, and some operators run neither. Cat-1 bis runs on LTE and inherits the broadest footprint, in exchange for more power and a larger module. Network sunsets add time to the decision: a device designed around 2G fallback needs a plan for the day that fallback disappears, and a module certified only for 2G is a stranded asset.
Roaming support is not uniform either. LTE-M roaming is more common than NB-IoT roaming, and even where roaming exists, permanent-roaming rules may limit how long a foreign profile can stay. Ask for the operator and band list per destination, with the date it was checked. Ask which bearer the quote is for, because a multi-mode module does not mean every mode is enabled or certified.
Try it: size a tracker
A tracker reports a position every 60 seconds and runs on a 5,000 mAh battery. Open the battery estimator with the tracker preset and read the projected life. Then set the interval to 300 seconds and compare.
The expected result is a longer life at the slower interval, because the radio wakes less often. If the change is small, the report size or the wake-up path is doing more work than the interval. That is the number to bring to the module discussion.
What to check before you commit
Ask for the market and band list with the date it was checked.
Check what you learned
-
A camera uploads a JPEG on motion. Which bearer fits, and why?
Cat-4, because the uplink payload and burst need capacity. NB-IoT and LTE-M are built for small, infrequent messages.
-
Why can a five-bar NB-IoT device still be slow?
Bars show signal strength, not capacity. NB-IoT trades rate for reach, and the device may be in a long sleep cycle or sharing a narrow channel.
-
What decides whether a module can roam in a destination?
The operator pair and the roaming agreement, plus the module's band support and certification. The bearer label alone does not decide it.
Answers are revealed on request. Nothing is scored, stored or sent.
FAQ
Can one device support several bearers?
What throughput do I need?
Does NB-IoT hand over between cells?
Can these modules roam?
Do any of them carry voice?
Sources
- GSMA NB-IoT: standards-based LPWA with deep coverage
- GSMA LTE-M: LPWA on the LTE installed base (3GPP Release 13, Cat-M1)
- 3GPP TS 36.306: UE radio access capabilities
- 3GPP TS 36.101: E-UTRA user equipment radio transmission and reception (operating bands)
- 3GPP TS 38.101-1: NR user equipment radio transmission and reception, Range 1
- 3GPP TS 24.301: NAS protocol for Evolved Packet System
- 3GPP TS 23.682: architecture enhancements for communications with packet data networks and applications
- 3GPP TS 36.304: UE procedures in idle mode
Terms you'll meet
Related
- Permanent roaming, country by country
How long a foreign SIM may roam before it needs a local profile, for Brazil, Mexico and Colombia, with the decision path to the right product.
- SGP.32 for IoT devices
What SGP.32 changes for IoT fleets, which devices qualify, and why SGP.02 devices cannot be upgraded over the air.
- eUICC identifier (EID)
The eUICC identifier, separate from the subscription.
Related products
Put this to work
Tell us the traffic, the destination and the measurement you need; we reply with the next step.