# Duty Cycle - Time on Air

**URL:** <https://www.thethingsnetwork.org/forum/t/duty-cycle-time-on-air/122>\
**Category:** TTN Network and Services\
**Created:** [September 24, 2015, 11:20am UTC](https://www.thethingsnetwork.org/forum/t/duty-cycle-time-on-air/122 "2015-09-24T11:20:20Z")\
**Posts on this page:** 1\
**Showing post:** 23

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**Author:** ![arjanvanb](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/arjanvanb/32/46626_2.png) [@arjanvanb](https://www.thethingsnetwork.org/forum/u/arjanvanb)\
**Post date:** [May 9, 2017, 6:27pm UTC](https://www.thethingsnetwork.org/forum/t/duty-cycle-time-on-air/122/23 "2017-05-09T18:27:11Z")

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> [@hieubk](#):
>
> ductycycle=1% means:
> 
> 1. Sub-band available on 36s/1h.

You’d wish, but no:

1. The duty cycle should be taken into account each time you send. It’s not some hourly or daily total, so you cannot send 36 seconds and then be quiet for the remaining hour. Instead, [from the specifications](https://www.lora-alliance.org/portals/0/specs/LoRaWAN%20Specification%201R0.pdf#page=34):

2. The duty cycle is meant to lower the chances that two nodes send simultaneously. (Which would cause collisions and data loss if that happens.) However, if each node would use the maximum 1% duty cycle (assuming they would never send simultaneously with some other nodes, and would do perfect channel-hopping using 8 channels), then a gateway could only support 800 nodes! (Okay, a bit more if nodes happen to use different spreading factors, but far less as nodes send randomly.)

3. The [TTN Fair Access Policy](https://www.thethingsnetwork.org/forum/t/limitations-data-rate-packet-size-30-seconds-uplink-and-10-messages-downlink-per-day-fair-access-policy/1300) nicely summarizes 1. and 2. by limiting air time to 30 seconds per node **per day**.

  

> [@hieubk](#):
>
> All nodes can use it or each node can use this time ?

It is per node. Nodes do not know what other nodes did.

  

> [@hieubk](#):
>
> A node1 sent one frame on x second in sub-band A. Sub-band will off with only node1 on x\*99 second ?

I don’t understand. Seems like this is answered above.

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