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CWT: Wireless LAN Hardware and Installation

CWT · Work through your exam, one topic at a time.

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Wireless LAN Hardware and Installation

Wireless LAN Hardware and Installation

This domain tests the physical deployment: access points, controllers, antennas, cabling, power, mounting, and safety. Questions often ask you to select hardware or spot an installation error.

Power over Ethernet

  • 802.3af (Type 1) delivers up to 15.4 W at the PSE and 12.95 W at the PD; 802.3at (Type 2) delivers 30 W at the PSE and 25.5 W at the PD; 802.3bt (Type 3/4) provides 60 W or 90 W at the PSE.
  • A switch's total PoE budget is shared across ports; an AP that boots at one class may renegotiate to a higher class. Check both per-port class and aggregate budget.
  • PoE injectors and midspans are valid where the switch lacks PoE, but they add a failure point and may not support 802.3bt.

Antennas and RF plumbing

  • Omnidirectional antennas radiate in a doughnut pattern; semi-directional and highly directional antennas focus energy and add gain. Gain comes from narrowing the beamwidth, not from amplifying total power.
  • Polarization must match between endpoints; a 90-degree mismatch can cost 20 dB or more. Downtilt aims coverage toward the floor in high-ceiling venues.
  • Use the correct connector (N-type, RP-SMA), keep jumper runs short, and account for cable loss at the operating frequency. Weatherproof outdoor connectors and use drip loops.

Mounting, safety, and infrastructure

  • Mount APs below the ceiling, clear of metal ducts, elevator shafts, and fluorescent ballasts. Avoid mounting inside metal enclosures.
  • Ground outdoor antennas and use lightning arrestors; follow local electrical code. Use plenum-rated cable in air-handling spaces.
  • Controllers can be hardware, virtual, or cloud-managed; standalone APs suit small sites. Mesh and point-to-point bridges need line of sight and Fresnel clearance.

Worked example

A 24-port PoE switch has a 370 W budget. You plan 10 APs: eight draw 12.95 W and two draw 25.5 W. Total = (8 × 12.95) + (2 × 25.5) = 103.6 + 51 = 154.6 W, which fits. But if the switch only supports 802.3af on all ports, the two 25.5 W APs will be underpowered or refuse to enable all radios, so verify per-port standard, not just total watts.

Traps

  • Assuming any PoE switch can power any AP; check class, standard, and budget.
  • Ignoring cable loss and connector loss in the link budget.
  • Mounting antennas near metal or with incorrect polarization.
  • Forgetting grounding and surge protection outdoors.