Cellular IoT and 5G: NB-IoT, LTE-M, eSIM and private networks
In short: Cellular IoT uses mobile networks to connect devices that are far from Wi-Fi. NB-IoT and LTE-M suit small, battery-powered sensors, 5G RedCap fills the middle ground, and eSIM makes it easier to change operator. Private networks and private APNs keep device traffic off the public internet.
Why use cellular for IoT
Wi-Fi and Bluetooth work well inside a building you control. Many IoT devices live elsewhere: water meters under pavements, trackers on shipping containers, sensors on wind turbines, payment terminals in taxis. For these, a mobile network is attractive because the coverage already exists, the spectrum is licensed (so interference is managed) and the SIM gives every device a strong, operator-backed identity.
The trade-off is cost and power. A normal 4G modem draws too much current for a sensor that must run for years on a battery, and a monthly data plan per device adds up across thousands of units. That is why the mobile industry created low-power options specifically for machines.
NB-IoT, LTE-M and 5G for machines
| Technology | Good for | Limits |
|---|---|---|
| NB-IoT (Narrowband IoT) | Static meters and sensors sending a few bytes a day; reaches basements and deep indoor spots | Low data rate, high latency, poor support for moving devices |
| LTE-M (LTE Cat-M1) | Trackers, wearables, alarms; supports handover while moving and is fast enough for firmware updates | Slightly more power than NB-IoT |
| 5G RedCap (Reduced Capability) | Industrial sensors, cameras, wearables that need more speed than LTE-M but less cost than full 5G | Newer, so module choice and coverage are still growing |
| 4G / 5G broadband | Gateways, CCTV, vehicles, routers that aggregate many devices | Highest power and data cost |
The 5G standards describe three service families: eMBB (enhanced mobile broadband) for speed, URLLC (ultra-reliable low-latency communication) for control systems, and mMTC (massive machine-type communication) for huge numbers of cheap sensors. In practice, NB-IoT and LTE-M are the technologies that deliver massive IoT on 5G networks, so a device using them today is not a dead end.
Two power-saving features matter for battery life. PSM (Power Saving Mode) lets a device sleep for hours while staying registered, and eDRX (extended Discontinuous Reception) stretches the gap between checks for incoming messages. The catch is that a sleeping device cannot be reached instantly, so your cloud side must queue commands.
eSIM and iSIM
A traditional plastic SIM ties a device to one operator. Swapping SIMs in 10,000 sealed sensors is not realistic. An eSIM (embedded SIM, technically an eUICC) is soldered to the board and can hold operator profiles that are downloaded and switched remotely. The GSMA publishes the remote provisioning specifications, including a variant designed for IoT devices that have no screen or user. An iSIM goes further and builds the SIM function into the modem chip itself, saving space and cost.
From a security view, the SIM is a tamper-resistant secure element. It stores the subscriber key used in the network's mutual authentication, and 5G adds concealment of the permanent subscriber identity over the air. Protect the remote profile management process carefully: whoever controls profile switching controls connectivity for the whole fleet.
Private networks and private APNs
By default, a cellular IoT device gets internet access like a phone, which means it can be reached from, or talk to, anywhere. Two options shrink that exposure:
- Private APN (Access Point Name): the operator routes your SIMs into a dedicated gateway that connects only to your data centre or cloud, usually over an IPsec VPN or a direct link. Devices get private IP addresses and no route to the internet.
- Private 4G/5G network: you run your own radio network and core (or buy it as a managed service) on a factory site, port or campus, using local licences or shared spectrum that regulators make available in many countries. You control coverage, capacity and who joins.
Tip: even on a private APN, still use TLS from device to platform. The APN protects the path; TLS protects the data and proves you are talking to the right server.
Security checklist for cellular IoT
- Choose a private APN or a fixed set of allowed destinations; block inbound connections from the internet.
- Lock SIMs to the device (IMEI lock) so a stolen SIM cannot be used in a phone to run up charges.
- Use the operator portal to alert on unusual data use, which is a common sign of a compromised or misused device.
- Encrypt application traffic end to end and use per-device credentials, not one shared password.
- Plan for network sunsets: 2G and 3G shutdowns have already stranded devices, so pick LTE-M, NB-IoT or 5G for new designs.
Practice
A water company needs meters in basements that send one reading a day for ten years. Which technology fits best?
Why does a device using PSM not respond immediately to a command from the cloud?
What does a private APN protect against?
Key takeaways
- NB-IoT suits tiny, static, low-power sensors; LTE-M suits moving devices and updates.
- 5G RedCap covers mid-rate devices; NB-IoT and LTE-M deliver massive IoT on 5G.
- eSIM and iSIM let you change operator profiles remotely without touching the device.
- A private APN or private 5G network keeps devices off the public internet.
- Still use TLS and per-device credentials, and watch data usage for misuse.
Original content written by Mohamed Fayas for FM TecHub. © 2026 FM TecHub. You're welcome to share a link to this page; please don't copy the text elsewhere without permission.