CWS CWS Wireless Client Devices 5 — Questions and Answers
Question 1: A client connected at 802.11n HT40 on 2.4 GHz is experiencing frequent retransmissions. What is the most likely root cause?
- The AP does not support MIMO
- HT40 on 2.4 GHz overlaps with adjacent-channel BSSs causing heavy co-channel interference (Correct answer)
- The client's MCS index is too high
- WMM is not enabled on the AP
Correct answer: HT40 on 2.4 GHz overlaps with adjacent-channel BSSs causing heavy co-channel interference
40 MHz channels on 2.4 GHz consume most of the available spectrum, causing severe interference with neighboring networks.
Question 2: Which driver or OS-level setting on a Windows laptop most directly controls whether the Wi-Fi adapter scans for better APs while connected?
- Preferred Band setting
- Roaming Aggressiveness (Correct answer)
- 802.11n/ac mode
- Transmit Power setting
Correct answer: Roaming Aggressiveness
The Roaming Aggressiveness setting in the Windows Wi-Fi adapter advanced properties controls how often and at what signal threshold the client scans for better APs.
Question 3: What is the purpose of the 802.11v BSS Transition Management feature from a client perspective?
- It forces the client to use WPA3
- It allows the AP to suggest that the client roam to a different AP (Correct answer)
- It enables multi-band operation
- It reduces the association time
Correct answer: It allows the AP to suggest that the client roam to a different AP
802.11v BSS Transition Management lets the AP send requests/suggestions for a client to roam, enabling load balancing and steering.
Question 4: A wireless VoIP client experiences choppy audio only when roaming between APs. Which combination of 802.11 amendments best addresses this issue?
- 802.11a and 802.11b
- 802.11k, 802.11r, and 802.11v (Correct answer)
- 802.11ac and 802.11n
- 802.11i and 802.11e
Correct answer: 802.11k, 802.11r, and 802.11v
802.11k (neighbor reports), 802.11r (fast roaming), and 802.11v (BSS transition) together minimize roam latency for real-time applications.
Question 5: Which value in a client's received frame indicates the modulation and coding scheme used, directly affecting the data rate?
- RSSI
- MCS index (Correct answer)
- TSF timer
- NAV duration
Correct answer: MCS index
The MCS index defines the combination of modulation order, coding rate, and guard interval that determines the PHY data rate.
Question 6: When a client uses OKC (Opportunistic Key Caching), what is being reused during a roam?
- The client's MAC address
- The PMK cached from a previous association to speed up re-authentication (Correct answer)
- The AP's beacon interval
- The DHCP lease from the previous subnet
Correct answer: The PMK cached from a previous association to speed up re-authentication
OKC allows a client to reuse a cached PMK at a new AP without re-running full EAP authentication, reducing roam latency in WPA2-Enterprise networks.
Question 7: A client NIC reports a Receive Sensitivity of -95 dBm at MCS 0. What does this value represent?
- The maximum transmit power of the NIC
- The weakest signal level at which the NIC can reliably decode frames at that MCS (Correct answer)
- The noise floor of the environment
- The minimum RSSI required for WPA3 association
Correct answer: The weakest signal level at which the NIC can reliably decode frames at that MCS
Receive sensitivity is the minimum signal power level at which the receiver can correctly decode packets at a given MCS with an acceptable error rate.
CWS CWS Wireless Client Devices 5
A client connected at 802.11n HT40 on 2.4 GHz is experiencing frequent retransmissions.
What is the most likely root cause?