LPWAN and IoT
Low-power wide-area networks for sensors and meters. LoRa and LoRaWAN, the 3GPP options NB-IoT and LTE-M, the state of Sigfox, regional duty-cycle limits and how to reason about battery life.
Overview
A low-power wide-area network (LPWAN) trades data rate for range and battery life. A soil sensor or water meter sends a few bytes a few times an hour and must run for years on one cell. The radios that serve it fall into two camps. Unlicensed systems such as LoRaWAN run in sub-GHz bands shared under rules on power and duty cycle. Cellular systems, NB-IoT and LTE-M, run in operators’ licensed LTE spectrum. This hub is for engineers who choose between them, plan coverage, or estimate battery life.
Key ideas
LoRa and LoRaWAN
LoRa is Semtech’s spread spectrum modulation, derived from chirp spread spectrum, according to Semtech. LoRaWAN is the MAC layer and system architecture above it, maintained by the LoRa Alliance. According to the LoRa Alliance, a network has end devices, gateways, network servers and application servers in a star-of-stars topology. End devices reach gateways over single-hop radio links. Gateways convert between radio packets and IP packets and relay them to a central network server. The Alliance also states that LoRaWAN has been approved as an international standard by ITU.
A typical LoRa radio is the Semtech SX1262. Semtech’s product page lists continuous coverage from 150 MHz to 960 MHz, up to +22 dBm output, sensitivity down to −148 dBm, and LoRa plus (G)FSK modulation. Sensitivity improves as the data rate drops, so the best figure comes with the longest airtime. Every step down in data rate buys link budget and costs energy and channel time.
NB-IoT and LTE-M
3GPP added three cellular IoT technologies in Release 13, according to its cellular IoT article. NB-IoT is a largely new radio that can operate in a system bandwidth as small as 200 kHz. It can be deployed stand-alone, inside an LTE carrier or in an LTE carrier’s guard band. LTE-M builds on LTE with low-cost device categories such as Cat-M1 and Cat-M2, and supports FDD, half-duplex FDD and TDD. EC-GSM-IoT extends GPRS coverage. The cellular options bring operator coverage, licensed spectrum and mobility, at the price of a subscription and a more complex modem. They also appear in 3GPP’s non-terrestrial work from Release 17, covered in the satellite and NTN hub.
Sigfox at the time of writing
Sigfox ran an ultra-narrowband network of its own. In February 2022 the company was in receivership, according to RCR Wireless. On 21 April 2022 the Commercial Court of Toulouse confirmed UnaBiz as the new owner, as RCR Wireless reported. The Sigfox site now presents Sigfox 0G as a technology run by UnaBiz, and its newest news item is from January 2025. We could not confirm current coverage or operator figures, so check with the network operator in your country before designing for it.
Duty cycle and battery life
In Europe, the harmonised standard for short range devices in the 863 to 870 MHz band is ETSI EN 300 220-2 (V3.2.1). In the 868.0 to 868.6 MHz sub-band it allows 25 mW e.r.p. with a duty cycle of at most 1% or polite spectrum access. A 1% duty cycle means 36 s of transmission per hour. Some neighbouring sub-bands allow only 0.1%. Network operators can add their own limits. The Things Network’s duty cycle page sets a fair-use policy of 30 s of uplink airtime and 10 downlinks per device per day on its public sandbox.
Battery life is a budget, not a datasheet line. Add up the charge for each transmission, each receive window, sensor reads and sleep current, then divide the cell’s usable capacity by the daily total. Sleep current and the receive windows after each uplink can dominate. Multi-year figures such as the LoRa Alliance’s “10+ years” are the vendor’s claims under favourable assumptions. Raza and co-authors compare the main LPWAN technologies in Low Power Wide Area Networks: An Overview (2017). Adelantado and co-authors show how duty cycle limits capacity in Understanding the Limits of LoRaWAN (2017).
Where to start
Begin with Decibels and link budgets and Noise, SNR and capacity, since LPWAN design is link budget arithmetic. The LoRaWAN link budget and coverage project applies it to a real deployment question. The link budgets and noise hub and the decibels and link budget reference hold the formulas. Field robots that report over long-range links are covered on Robotics Field Guide’s aerial and field robots hub.
Tools and platforms
| Tool | What for | Licence or terms |
|---|---|---|
| USP | Semtech’s maintained radio and LoRaWAN software platform, successor to LoRaMac-node (archived 2 November 2026) | Clear BSD |
| The Things Stack | LoRaWAN network server behind The Things Network’s public sandbox | See the vendor’s terms |
| ChirpStack | Open-source LoRaWAN network server | MIT |
| LoRa Alliance resource hub | LoRaWAN and regional parameters specifications | LoRa Alliance terms |
Platform hubs: open-source tools, Nordic Semiconductor and Qualcomm.
Common mistakes
- Planning on the best-case sensitivity while also assuming the highest data rate.
- Forgetting the duty cycle when sizing message rates. It limits each device and, through gateway downlinks, the whole network.
- Treating an unlicensed network as guaranteed service. Interference and other users share the band.
- Quoting battery life without the current profile and message rate behind it.
- Assuming an NB-IoT or LTE-M module works on every network. Check which bands and features the local operator supports.
- Using a frequency plan from one region in another. The LoRa Alliance regional parameters differ by country.
Going deeper
- Raza, Kulkarni and Sooriyabandara, Low Power Wide Area Networks: An Overview, IEEE Communications Surveys and Tutorials, 2017.
- Adelantado and co-authors, Understanding the Limits of LoRaWAN, IEEE Communications Magazine, 2017.
- ETSI EN 300 220-2 V3.2.1, short range devices from 25 MHz to 1000 MHz.
- 3GPP, The Cellular Internet of Things.