# Kerlink downlink issue

**URL:** <https://www.thethingsnetwork.org/forum/t/kerlink-downlink-issue/3089>\
**Category:** Kerlink Gateways\
**Created:** [August 10, 2016, 7:28am UTC](https://www.thethingsnetwork.org/forum/t/kerlink-downlink-issue/3089 "2016-08-10T07:28:03Z")\
**Posts on this page:** 1\
**Showing post:** 13

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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:** [April 7, 2017, 1:36pm UTC](https://www.thethingsnetwork.org/forum/t/kerlink-downlink-issue/3089/13 "2017-04-07T13:36:09Z")

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> [@MAlen](#):
>
> we did set up 10 nodes to send at approximately the same time

Then your problem might also be the duty cycle of the gateway. TTN Console will nicely tell you when it cannot find a gateway that can handle the downlink. (Which, for example, also happens [when many nodes try to do OTAA at about the same time](https://www.thethingsnetwork.org/forum/t/activation-not-valid-no-gateways-available/5649).) I don’t know what your server does in that case. (This is one of the reasons TTN’s fair access policy [allows for only a few downlinks per day](https://www.thethingsnetwork.org/forum/t/limitations-data-rate-packet-size-30-seconds-uplink-and-10-messages-downlink-per-day-fair-access-policy/1300).)

Also beware that current gateways are half-duplex. When transmitting a downlink they cannot receive any uplinks. (Yet another reason for TTN’s fair access policy to limit the downlinks.)

> [@MAlen](#):
>
> This would be true for both @brocaar’s and TTN NS, or any for that matter that do not send a downlink in exact moment when it needs to be sent by a GW

…but TTN’s network server _is_ waiting until the very last moment, allowing for a little network delay.

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