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DFS
DFS in RAP
RAP performs the following steps as a response to radar detection:
1.
2.
3.
4.
5.
6.
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8.
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10.
DFS in MAP
MAP performs the following steps as a response to radar detection:
1.
2.
3.
4.
5.
6.
Cisco Aironet 1520, 1130, 1240 Series Wireless Mesh Access Points, Design and Deployment Guide, Release 6.0
OL-20213-01
RAP sends a message to the controller that the channel is infected with Radar. Channel is marked
as infected channel on the RAP and on the controller.
RAP blocks the channel for 30 minutes. This 30 minutes period is called non-occupancy period.
Controller sends the TRAP, indicating that the radar has been detected on the channel. TRAP
remains until the non-occupancy period expires.
RAP has 10 seconds to move away from the channel. This is called channel move time. This is
defined as the time for the system to clear the channel and is measured from the end of the radar
burst to the end of the final transmission on the channel.
RAP enters the quiet mode. In the quiet mode, RAP stops data transmissions. Beacons are still
generated and probe responses are still delivered. Quite mode exists until the channel move time is
over (10 seconds).
Controller picks up a new random channel and sends the channel information to the RAP.
RAP receives the new channel information and sends channel change frames. (unicast, encrypted)
to MAPs, and each MAP sends the same information to its lower children down the sector. Each
mesh access point sends the channel change frames once every 100 msecs for a total of five times.
RAP tunes to the new channel and enters into the silent mode. During the silent mode, only the
receiver is ON. RAP keeps scanning the new channel for any radar presence for 60 seconds. This is
called channel availability check (CAC).
MAPs tune to the new channel and enter into the silent mode. During the silent mode, only the
receiver is ON. MAPs keeps scanning the new channel for any radar presence for 60 seconds.
If radar is not detected, RAP resumes full functionality on this new channel and the whole sector
tunes to this new channel.
MAP sends a radar seen indication to the parent and ultimately to the RAP indicating that the
channel is infected. RAP sends this message to the controller. The message will look like it is
coming from the RAP. MAP, RAP and controller mark the channel as infected for 30 minutes.
MAP blocks the channel for 30 minutes. This 30 minutes period is called non-occupancy period.
Controller sends the TRAP, indicating that the radar has been detected on the channel. TRAP
remains until the non-occupancy period expires.
MAP has 10 seconds to move away from the channel. This is called channel move time. This is
defined as the time for the system to clear the channel and is measured from the end of the radar
burst to the end of the final transmission on the channel.
MAP enters the quiet mode. In the quiet mode, MAP stops data transmissions. Beacons are still
generated and probe responses are still delivered. Quite mode exists until the channel move time is
over (10 seconds).
Controller picks up a new random channel and sends the channel to the RAP.
Troubleshooting
141
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