Rf Detection Scans; Dynamic Frequency Selection (Dfs) - D-Link DWS-1008 - AirPremier MobileLAN Switch Product Manual

All radios continually scan for other RF transmitters. Radios perform passive scans and active scans:
• Passive scans—The radio listens for beacons and probe responses.
• Active scans—The radio sends probe any requests (probe requests with a null SSID name)
to solicit probe responses from other access points.
Passive scans are always enabled and cannot be disabled. Active scans are enabled by default but can
be disabled on a radio-profile basis.
Radios perform both types of scans on all channels allowed for the country of operation. (This is the
regulatory domain set by the set system countrycode command.) 802.11b/g radios scan in the 2.4 GHz
to 2.4835 GHz spectrum. 802.11a radios scan in the 5.15 GHz to 5.85 GHz spectrum.
Both enabled radios and disabled radios perform these scans.
The active-scan algorithm is sensitive to high-priority (voice or video) traffic or heavy data traffic. Active-
scan scans for 30 msec once every second, unless either of the following conditions is true:
• High-priority traffic (voice or video) is present at 64 Kbps or higher. In this case, active-
scan scans for 30 msec every 60 seconds.
• Heavy data traffic is present at 4 Mbps or higher. In this case, active-scan scans for 30
msec every 5 seconds.
On a disabled radio, the radio is dedicated to rogue detection and scans on each channel in round-robin
fashion.
Some regulatory domains require conformance to ETSI document EN 301 893. Section 4.6 of that
document specifies requirements for Dynamic Frequency Selection (DFS). These requirements apply
to radios operating in the 5 GHz band (802.11a radios).
In countries where Dynamic Frequency Selection (DFS) is required, MSS performs the appropriate
check for radar. If radar is detected on a channel, the AP radio stops performing active scans on that
channel in accordance with DFS.
However, the radio continues to passively scan for beacons from rogue devices.
When an AP radio detects radar on a channel, the radio switches to another channel and does not attempt
to use the channel where the radar was detected for 30 minutes. MSS also generates a message.
Note: The RF Auto-tuning feature must be enabled. Otherwise MSS cannot change the channel.
D-Link DWS-1008 User Manual

RF Detection Scans

Dynamic Frequency Selection (DFS)