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CWLS: CWLS Exam Domain: Wireless LAN Fundamentals, Security, and Deployment

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

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CWLS Exam Domain: Wireless LAN Fundamentals, Security, and Deployment

The CWLS domain tests whether you can reason from RF behavior through 802.11 configuration to a secure, survey-verified WLAN. Questions are scenario-based: you are given constraints such as band, channel width, EIRP limit, authentication method, or client density, and must select the design or diagnose the symptom. Expect terminology such as RSSI, SNR, EIRP, co-channel interference, 802.1X/EAP, WPA3-SAE, CAPWAP, DFS, and PoE.

Core rules and concepts

  • RF units matter: dBm is absolute power, dBi is antenna gain relative to isotropic, and dB expresses loss or gain. EIRP = radio power (dBm) − cable loss (dB) + antenna gain (dBi). A 3 dB change doubles or halves power; 10 dB is a tenfold change.
  • SNR is signal minus noise, while RSSI is a vendor-specific received-strength indicator. A strong RSSI with high noise can still yield a poor link.
  • In 2.4 GHz, the non-overlapping 20 MHz channels are 1, 6, and 11. In 5 GHz, favor 20/40 MHz for reuse and account for DFS/TPC channels; wider channels raise throughput but consume spectrum and increase co-channel interference.
  • 802.11ac introduced MU-MIMO and wider 5 GHz channels; 802.11ax adds OFDMA, uplink MU-MIMO, and BSS coloring. Match client capabilities rather than assuming the newest AP feature is always used.
  • WPA2-PSK is personal; WPA2-Enterprise uses 802.1X/EAP. WPA3-SAE replaces the PSK handshake and PMF protects management frames. Avoid WEP/TKIP and isolate guest traffic with VLANs.
  • Deployment requires a site survey, AP placement for coverage and capacity, PoE budget checks, and CAPWAP control/data path awareness.

Worked example

An AP radio transmits at 20 dBm. The cable loses 2 dB, and the antenna has 5 dBi gain. EIRP = 20 − 2 + 5 = 23 dBm. If the regulatory limit for that band and mode is 20 dBm EIRP, the design is 3 dB over. Reduce the radio to 17 dBm (17 − 2 + 5 = 20 dBm) or use a lower-gain antenna. Next, a client reports RSSI −68 dBm and noise −92 dBm: SNR = −68 − (−92) = 24 dB. That is workable for many MCS rates but not automatically “excellent”; verify retries, channel utilization, and client capability.

Traps that cost marks

Do not mix dBm and dBi, ignore cable loss, or assume maximum EIRP is always best-it increases co-channel interference. Do not treat RSSI as SNR. Do not use 40 MHz in 2.4 GHz for reuse. Do not forget DFS behavior or PoE class limits. Do not call WPA2-PSK “enterprise” or overlook management-frame protection.