In radio communications, especially in unlicensed bands like those used by LoRaWAN®, spectrum sharing is essential. Since many devices coexist on the same frequencies, regulators impose limits on how often each device can transmit. This is where the concept of duty cycle comes into play.
Duty cycle refers to the percentage of time a device is allowed to transmit on a given frequency during a defined period. For example, a 1% duty cycle means a device can transmit for 1 second out of every 100 seconds.
In LoRaWAN networks, duty cycle compliance affects:
“This article clarifies what duty cycle is, how it works at different levels (device, channel, sub-band), and how to design your LoRaWAN applications to remain compliant while optimizing network performance.“
At its simplest, duty cycle is the fraction of time a device spends transmitting within a given period.
Example: If a device transmits for 2 seconds every 10 seconds, it has a duty cycle of 20%.
This mechanism is crucial in shared radio environments, where devices must cooperate to avoid congesting the frequency band. Regulators enforce duty cycle limits to prevent spectrum abuse.
In LoRaWAN, we distinguish between:
Each level affects how often and how much data a device can send.
Let’s take a basic example:
A device transmits for 2 seconds and then must remain silent for 8 seconds to respect a 20% duty cycle on a single channel. This leads to transmission pauses, or “off-air” periods, that are mandatory to remain compliant.
Application Implications
LoRaWAN devices can use several channels simultaneously. This opens the possibility of increasing total transmission time without violating per-channel duty cycles.
Example : A device using three channels, each limited to 20% duty cycle, can transmit 2 seconds every 10 seconds per channel — meaning up to 6 seconds total in that 10-second window, or an effective device duty cycle of 60%.
Trade-Off
In the EU868 MHz LoRaWAN band, the spectrum is divided into sub-bands (K, L, M, N, P, Q), each with specific duty cycle limits. Channels are assigned to these sub-bands based on their frequency.
Example Imagine 3 channels:
The device must track and respect the duty cycle limit for each sub-band independently.
Impact on Network Design
In the EU, duty cycle limits for the 868 MHz ISM band are defined by the ETSI EN300.220-2 V3.2.1 standard. These limits vary by sub-band, as shown below:
| Sub-band | Frequency Range | Max Duty Cycle |
|---|---|---|
| K | 863 – 865 MHz | 0.1% |
| L | 865 – 868 MHz | 1% |
| M | 868 – 868.6 MHz | 1% |
| N | 868.7 – 869.2 MHz | 0.1% |
| P | 869.4 – 869.65 MHz | 10% |
| Q | 869.7 – 870 MHz | 1% |
These limits are legally binding and apply regardless of the network type (public or private). Additionally, frequencies used for OTAA joins are also subject to regulation — typically limited to 1%.
Why It Matters ? If a device exceeds these limits, it is non-compliant, which can lead to:
Even though LoRaWAN is designed for flexibility, fair use policies help ensure equitable access, especially in public networks.
On Actility’s public or community networks (e.g., ThingPark Community), fair use guidelines typically recommend:
These limits help ensure reliable service across all users. On private networks using ThingPark Enterprise, there are no such limits, but regulatory duty cycle rules still apply.
Designers and developers must proactively manage their devices’ airtime to stay compliant.
Tools & Strategies
Staying within limits also helps preserve battery life, another key consideration in LoRaWAN deployments.
Some LoRa radio modules enforce duty cycle limits at the firmware level.
Example: Microchip RN2483
Developer Strategy
To avoid blocking:
About Actility
Actility, one of the co-inventors of LoRaWAN® technology and a founding member of the LoRa Alliance, is the leader in industrial-grade low-power wide-area network (LPWAN) connectivity and IoT tracking solutions. Actility’s ThingPark™ platform, which supports multi-radio connectivity (LoRaWAN®, NB-IoT, LTE-M), powers the majority of public networks and numerous private and enterprise networks worldwide. Through its subsidiary Abeeway, Actility offers patented ultra-low power, multi-radio trackers and comprehensive indoor and outdoor geolocation services. Additionally, the ThingPark Market boast the largest catalog of LoRaWAN® devices, gateways, and solutions available.
Media contact : marketing@actility.com – https://www.actility.com/contact/
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