We aren’t talking about the DFS requirement for certain 5GHz bands for outdoor use. CAPsMAN is for deploying, configuring, and maintaining APs for indoor use in an 802.11 LAN.
The CAPsMAN auto frequency basically just instructs the CAP to use “frequency=auto” on the wireless interface. And “frequency=auto” is equivalent to “dfs-mode=no-radar-detect”, as Normis clarifies for us here: http://forum.mikrotik.com/t/v6-11-released/75450/22 – so, yeah, it isn’t listening for radar on the current channel.
I wasn’t talking about having the device in scanning mode to find interference on the current channel. I was talking about having the device in scanning mode in order to find other channels to switch to if interference is detected on the current one, or to actively look for a better channel to switch to even if no other distinct system is detected on the current one or if local RF conditions change since the last time it picked a channel.
RADAR detect is only looking for a specific type of wireless transmission, in order to avoid channels where RADAR transmission is taking place. As far as I know, it does not look for general noise, or for other 802.11 systems (except by accident, if a transmission from a neighboring 802.11 system on the same channel happens to match what it would interpret to be a RADAR pattern). The purpose of RADAR detect is not to have automatic channel co-ordination between 802.11 APs.
If radar-detect is enabled and RADAR is detected, my understanding is that the AP has to vacate the channel as soon as possible. This means that either the AP shuts down for a while while it performs another lengthy scan of the entire spectrum in order to pick a new channel, or that in order to avoid downtime, it picks a different channel at random and hopes there is no other system running on it. Neither is ideal. If there was a second radio in listen-only mode, then the AP would always have an up-to-date list of the possible good channels in the local vicinity that it could immediately hop to.
– Nathan