The wireless air interface is a virtual logical interface on an AP or terminal. Many factors affect the performance of the wireless air interface, but which of the following factors is not included?

Question

Options

• AInterference from non-WLAN devices
• BDifferences in terminal capabilities
• CSwitch forwarding capability
• DInterference from WLAN equipment

• A
  16% (11)
• B
  3% (2)
• C
  76% (53)
• D
  6% (4)

Explanation

C (Switch forwarding capability) is correct because a network switch operates at Layer 2 of the wired infrastructure - it has no direct involvement in the wireless air interface, which is purely a radio-frequency medium between APs and wireless terminals. Switch performance affects wired throughput downstream of the AP, not the air interface itself.

Why the distractors are wrong:

• A (Interference from non-WLAN devices) - microwave ovens, Bluetooth devices, and cordless phones all operate in overlapping frequency bands (e.g., 2.4 GHz) and directly degrade wireless signal quality.
• B (Differences in terminal capabilities) - a client with an older Wi-Fi standard (e.g., 802.11n) or weaker antenna forces the AP to negotiate lower data rates, directly impacting air interface performance.
• D (Interference from WLAN equipment) - neighboring APs on the same or overlapping channels cause co-channel or adjacent-channel interference, one of the most common air interface issues.

Memory tip: Think "air interface = everything that touches the radio signal." If it's wired (switch, router forwarding) it doesn't touch the air - if it touches or competes with the radio waves (interference, client hardware), it does.

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