LPWAN compared: LoRaWAN, Sigfox, NB-IoT and LTE-M

What LPWAN is for

Some IoT devices need to send a few bytes, a few times a day, from places with no Wi-Fi: meters in basements, sensors in fields, trackers on shipping containers. A low-power wide-area network (LPWAN) trades data rate for range and battery life. Messages are tiny and slow, but a single base station can cover kilometres and devices can last for years.

LoRaWAN

LoRa is a long-range radio modulation; LoRaWAN is the network protocol on top, maintained by the LoRa Alliance. It uses unlicensed sub-GHz bands (for example around 868 MHz in Europe and 915 MHz in the Americas), where duty-cycle rules limit how often a device may transmit. Devices do not connect to a specific gateway: every gateway in range forwards what it hears to a network server, which removes duplicates.

• Classes: Class A devices listen only briefly after sending (lowest power); Class B adds scheduled listening slots; Class C listens almost constantly (mains powered).
• Joining: Over-the-Air Activation (OTAA) derives fresh session keys at each join and is recommended. Activation by Personalisation (ABP) hard-codes session keys and is weaker.
• Security: AES-128 with separate keys for network integrity and application payload encryption, so the network operator need not see your data.

You can run your own private LoRaWAN or use a public or community network.

Sigfox, NB-IoT and LTE-M

Sigfox uses ultra-narrowband radio in unlicensed spectrum, with very small payloads (12 bytes uplink) and a strict daily message limit. It is run as an operator network; after financial difficulties in 2022 it was taken over by UnaBiz. Check local coverage and long-term availability before choosing it.

NB-IoT and LTE-M (also called LTE Cat-M1) are standards from the mobile industry body 3GPP that run on operators' licensed networks and use SIM-based authentication. Both support Power Saving Mode (PSM), where the device is unreachable for long periods, and extended Discontinuous Reception (eDRX), which stretches the gap between checks for incoming messages.

Security considerations

1. Prefer OTAA over ABP for LoRaWAN, and store root keys in a secure element.
2. Protect your network and join servers like any critical server; they hold or derive the keys.
3. Remember tiny payloads limit room for extra security headers, so design compact, authenticated message formats.
4. For cellular, use private APNs or operator VPN services so devices are not exposed on the public internet.
5. Firmware updates over LPWAN are slow or impractical on LoRaWAN and Sigfox; plan how devices will be patched.

Tip: LPWAN is for small data. If a design needs regular firmware updates or images, LTE-M or another cellular option is usually more realistic than LoRaWAN or Sigfox.