On Monday, October 24, 2016 4:16:02 PM CEST Johannes Berg wrote: > On Mon, 2016-10-24 at 15:42 +0200, Simon Wunderlich wrote: > > Otherwise, it would be pretty much impossible to perform CSAs to > > another DFS channel. > > I was told that to do that you'd need another NIC that's pre-CAC'ing > another channel.
Here is the portion from ETSI 301 893 v1.8.1 [1] (the most recent one to my
knowledege), section 4.7.1.4 which describes operation from master devices
(Access Points):
<snip>
b) A master device shall only start operations on Available Channels. At
installation (or reinstallation) of the equipment, the RLAN is assumed to have
no Available Channels within the band 5 250 MHz to 5 350 MHz and/or 5 470 MHz
to 5 725 MHz. In such a case, before starting operations on one or more of
these channels, the master device shall perform either a Channel Availability
Check or an Off-Channel CAC to ensure that there are no radars operating on
any selected channel. If no radar has been detected, the channel(s) becomes an
Available Channel(s) and remains as such until a radar signal is detected
during the In-Service Monitoring.
The Channel Availability Check or the Off-Channel CAC may be performed over a
wider bandwidth such that all channels within the tested bandwidth become
Available Channels.
NOTE 1:The initial Channel Availability Check may be activated manually at
installation or reinstallation of the equipment.
c) Once the RLAN has started operations on an Available Channel, then that
channel becomes an Operating Channel. During normal operation, the master
device shall monitor all Operating Channels (In-Service Monitoring) to ensure
that there is no radar operating within these channel(s). If no radar was
detected on an Operating Channel but the RLAN stops operating on that channel,
then the channel becomes an Available Channel.
NOTE 2:An RLAN is allowed to start transmissions on multiple (adjacent or non-
adjacent) Available Channels. In this case all these channels become Operating
Channels.
<snap>
As I interpret this, (b) states explicitly that we can have many available
channels. We only need to mark channels where we detect a radar.
BTW, there was also something like a 24h disconnect previously, which was
removed in 2009 [2].
Cheers,
Simon
[1] http://www.etsi.org/deliver/etsi_en/301800_301899/301893/01.08.01_60/
en_301893v010801p.pdf
[2] http://www.wlan-skynet.de/docs/rechtliches/etsi_301_893.shtml (german
only)
>
> johannes
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