300-425 · Question #322
Why is Dynamic Frequency Selection (DFS) important in WLAN design?
The correct answer is C. To enable usage of additional 5 GHz channels while avoiding radar interference. DFS allows Wi-Fi devices to access additional 5 GHz spectrum (U-NII-2 and U-NII-2e bands) that is shared with radar systems, requiring APs to detect and vacate channels when radar is present.
Question
Why is Dynamic Frequency Selection (DFS) important in WLAN design?
Options
- ATo allow use of radar-detected channels in 2.4 GHz
- BTo increase AP transmit power beyond regulations
- CTo enable usage of additional 5 GHz channels while avoiding radar interference
- DTo reduce co-channel interference on 6 GHz
How the community answered
(39 responses)- A3% (1)
- B3% (1)
- C87% (34)
- D8% (3)
Why each option
DFS allows Wi-Fi devices to access additional 5 GHz spectrum (U-NII-2 and U-NII-2e bands) that is shared with radar systems, requiring APs to detect and vacate channels when radar is present.
DFS applies exclusively to the 5 GHz band - the 2.4 GHz band has no radar-sharing requirements and does not use DFS.
DFS is a channel-switching mechanism for radar avoidance and has no relationship to transmit power levels or regulatory power limits.
DFS enables use of channels 52-144 in the 5 GHz band (U-NII-2 and U-NII-2e) which are otherwise restricted due to radar coexistence requirements. When an AP detects a radar signal on a channel, it must perform a Channel Availability Check and switch to a clear channel within the required time. This expands available spectrum while protecting radar operations from interference.
The 6 GHz band uses Automated Frequency Coordination (AFC) for incumbent protection, not DFS - and co-channel interference mitigation is handled separately by RRM mechanisms.
Concept tested: Dynamic Frequency Selection for 5 GHz radar avoidance
Source: https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/dfs.html
Topics
Community Discussion
No community discussion yet for this question.