CWNA V1.0 4 — Questions and Answers
Question 1: Which 802.11 QoS amendment introduced Wi-Fi Multimedia (WMM) to prioritize traffic by access category?
- 802.11e (Correct answer)
- 802.11i
- 802.11r
- 802.11k
Correct answer: 802.11e
802.11e defined EDCA (Enhanced Distributed Channel Access) and is the foundation for WMM, which prioritizes voice, video, best-effort, and background traffic.
Question 2: A technician measures a received signal of -67 dBm and a noise floor of -90 dBm. What is the SNR?
- 157 dB
- 23 dB (Correct answer)
- -23 dB
- 67 dB
Correct answer: 23 dB
SNR = Signal − Noise = −67 dBm − (−90 dBm) = 23 dB, indicating a clean signal well above the noise floor.
Question 3: Which 802.11 amendment enables fast BSS transition (fast roaming) to reduce handoff latency for voice and real-time applications?
- 802.11k
- 802.11r (Correct answer)
- 802.11v
- 802.11s
Correct answer: 802.11r
802.11r (Fast BSS Transition) pre-caches PMK security keys at neighboring APs to drastically reduce re-association time during roaming.
Question 4: What is the primary function of MU-MIMO in 802.11ac Wave 2 and 802.11ax access points?
- Encrypting data streams independently for each client
- Transmitting simultaneously to multiple clients using spatial streams (Correct answer)
- Increasing channel width to 160 MHz
- Reducing transmit power to minimize interference
Correct answer: Transmitting simultaneously to multiple clients using spatial streams
MU-MIMO (Multi-User MIMO) allows an AP to transmit unique spatial streams to multiple clients at the same time, increasing aggregate throughput.
Question 5: In WLAN design, what does the term 'cell overlap' refer to and what is the recommended minimum percentage?
- AP coverage areas should overlap 10–15% to prevent dead zones during roaming
- AP coverage areas should overlap 15–20% to ensure seamless roaming (Correct answer)
- AP coverage areas should overlap 50% to double signal strength
- AP coverage areas must never overlap to avoid co-channel interference
Correct answer: AP coverage areas should overlap 15–20% to ensure seamless roaming
A 15–20% cell overlap ensures clients maintain association while roaming between APs without experiencing coverage gaps.
Question 6: Which protocol is used in 802.1X enterprise WLAN authentication to encapsulate EAP over the wired network between the authenticator and authentication server?
- PEAP
- RADIUS (Correct answer)
- TACACS+
- Kerberos
Correct answer: RADIUS
RADIUS (Remote Authentication Dial-In User Service) is the protocol that carries EAP messages between the AP (authenticator) and the authentication server.
Question 7: What RF phenomenon occurs when a wireless signal reflects off surfaces and arrives at the receiver via multiple paths, potentially causing signal cancellation?
- Refraction
- Diffraction
- Multipath (Correct answer)
- Absorption
Correct answer: Multipath
Multipath occurs when reflected copies of the same signal arrive at different times and phases, which can cause destructive interference and reduced signal quality.
CWNA V1.0 4
Which 802.11 QoS amendment introduced Wi-Fi Multimedia (WMM) to prioritize traffic by access category?