In the WLAN backhaul scenario, due to the complex environment and high bandwidth requirements of the business, reasonable planning is required when designing and installing APs. Which of the…

Question

Options

• AIt is necessary to confirm in advance whether there are obvious obstacles on the propagation
• BCheck in advance whether there is interference in the Wi-Fi frequency band near the site
• CThe antenna installation height must be within the radius r of the building's high Fresnel zone
• DWhen selecting a directional antenna, the main lobe coverage of the MPP antenna should cover

• A
  10% (5)
• B
  6% (3)
• C
  82% (40)
• D
  2% (1)

Explanation

Option C states that antenna installation height must be within the Fresnel zone radius, which reverses the actual rule. Correct Fresnel zone practice requires that antennas be positioned high enough so that obstacles fall outside (specifically, at least 60% of the first Fresnel zone must remain clear). Placing antennas within that radius means obstacles are intruding into the propagation zone, which directly degrades signal quality - the opposite of good deployment.

Options A, B, and D are all valid, correct deployment practices:

• A (checking for obstacles) is essential because WLAN backhaul often relies on near-line-of-sight paths, and physical obstructions cause significant attenuation and multipath interference.
• B (checking for Wi-Fi band interference) is standard site survey practice, since 2.4 GHz and 5 GHz bands can be congested with neighboring networks and other RF sources.
• D (ensuring the MPP antenna's main lobe covers the target) is fundamental to directional antenna alignment - misalignment would simply waste the gain advantage of a directional antenna.

Memory tip: Think of the Fresnel zone as a "clearance bubble" around your signal path - you want obstacles out, not in. The word "within" in option C is the red flag; in Fresnel zone planning, "within" always means trouble.

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