Duty Cycle Clarification and Examples

Devices
1

I have been researching the duty cycle and implementation of duty cycle for a few days. There are some points that need to be clarified. My case only covers EU863-870 frequency plan. I hope many people benefit from this.

1. Per Sub-band or Per Channel Implementation

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How to Qualify a LoRaWAN™ Device in Europe, TN1300.01, Rev1.0, Page 7/10

While I’m not sure, I assume that duty cycle regulations are applied at the level of individual sub-bands, rather than on a per-channel basis. Band-48 (868-868.6) is mandatory for end-device implementation, resulting in the duty cycle being distributed across its channels. In this scenario, each channel is allocated a duty cycle of 1/3 of 1%. For the following examples, it is assumed that the duty cycle enforcement is applied at a per-sub-band level.

EXAMPLE TABLE
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Explanation

Example-1. 5 channels are available for Band-47 (865-868) and 3 channels are availale for Band-48 (868-868.6);

  • The first transmission within Band-47 (865-868) should follow 0.2% duty cycle rule per channel as 5 channel is allocated for this band. Following this calculation, the second transmission within this band must wait (2793.50 * 5 * 100 = 1396.75 seconds) approximately 23 minutes. Given that there is only a singular transmission during 1 hour, the duty cycle is respected.

  • The second transmission within Band-48 (868-868.6) should follow 0.333% duty cycle rule per channel as 3 channel is allocated for this band. Following the second transmission, waiting time for third transmission is (2793.5 * 3 * 100 = 838.05 seconds ) approximately 14 minutes. So, the third transmission should take place at minimum 14 minutes later. In this example, third transmission is emitted 30 minutes after the second, thereby duty cycle is respected.

Example-2. Different device, 3 channels are available for Band-47 (867.100 , 867.300 and 867.500) and 3 channels are availale for Band-48 (868-868.6);

  • No transmission for Band-47 (865-868)
  • I have 3 transmission at Band 47 (865-868). DC is 36 seconds and. Duty cycle per channel is 0.333%. After the transmission at 0+0, the minumum wait time is (2793.503100 = 838.5) approximately 14 minutes. So the next transmission should take place not before than 0+838.5. In this example, the second transmission at this band takes place at 0+600and duty cycle is not respected.

2. Duty Cycle For Gateways

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LoRaWAN™ 1.0.3 Specification

The screen shot is taken from LoRaWAN™ 1.0.3 Specification and I assume that the end-device does not cover gateways. I have seen comments suggesting that gateways, accepted as Lorawan network members, become subject to Duty Cycle limitations.
My first question is whether gateways are bound by Duty Cycle regulations. If yes, the implementation of Duty Cycle for gateways presents a more challenging case. Chirpstack does not enforce Duty Cycle, and the responsibility of implementation is delegated to the gateway.
I think, delegating this to gateways will not make it easier. When an end-device sends a “Confirmed Data Up” message, the backend server is expected to respond with an acknowledgment (ACK) message. When DC is enabled for gateways, communication sequence may be disrupted. For instance, if an end-device anticipates an ACK packet within a specific timeframe but doesn’t receive it due to Duty Cycle restrictions, it might attempt to resend the packet and this may lead to another violation of Duty Cycle.
The other issue is as the number of end-devices changes, duty cycle should be adjusted for gateways as well. This is another headache.

3. Multicast Channel Duty Cycle
Multicast channel uses 869525000 and it falls into the Band-54. Luckily duty cycle for this band is 10%.

EXAMPLE TABLE
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Explanation

Example-1. Single channel is availalbe for Band-54 (869.4-869.65)

  • The second transmission is initiated 5 seconds after the first transmission. Given a Duty Cycle of 10% for a single channel, the minimum waiting time is calculated as (1478.70 * 10 = 14780 ms), approximately 14.8 seconds. However, in this case, the second transmission does not follow DC rule as minimum wait time is 14.8 seconds, resulting in a violation of the Duty Cycle regulation.

Example-2. Single channel is availalbe for Band-54 (869.4-869.65). DR 5,4 and 3 is used.

  • After first transmission, minimum wait time is (118 * 10 = 1180 ms) 1.18 seconds. Second transmission took place 10 seconds later and DC is respected. Second transmission used DR 2 and minimum wait time after this transmission is (698.4*10 = 6.98 seconds). Duty cycle is respected for this band.

4. EC Duty Cycle Decison Change
How would field devices be impacted if there were a change in the ETSI’s technical specification. Band-47 (865-868) duty cycle is incresed to 1% from 0.1% (How to Qualify a LoRaWAN™ Device in Europe, TN1300.01, Rev1.0). If it’s about increasing, it’s not expected to result in significant result, unlike the reverse scenario could create serious trouble.

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