ACMA WLAN Design 3 — Questions and Answers
Question 1: What is the recommended minimum Received Signal Strength Indicator (RSSI) for a voice over WLAN deployment?
- -80 dBm
- -70 dBm
- -67 dBm (Correct answer)
- -55 dBm
Correct answer: -67 dBm
-67 dBm is the generally accepted minimum RSSI for voice-grade WLAN performance to ensure reliable roaming and call quality.
Question 2: In an Aruba network, what does the term 'cell breathing' refer to in WLAN design?
- APs automatically increasing power when clients connect
- Reducing AP transmit power to shrink coverage cells and reduce co-channel interference (Correct answer)
- The process of APs switching between 2.4 GHz and 5 GHz bands
- APs rebooting on a scheduled cycle to refresh RF state
Correct answer: Reducing AP transmit power to shrink coverage cells and reduce co-channel interference
Cell breathing refers to reducing AP transmit power to create smaller, non-overlapping coverage cells that minimize co-channel interference.
Question 3: Which deployment model is recommended when APs must be installed in locations without Ethernet cabling?
- Controller-based APs with PoE switches
- Mesh APs using wireless backhaul (Correct answer)
- Cloud-managed APs with fiber uplinks
- Autonomous APs with USB power
Correct answer: Mesh APs using wireless backhaul
Mesh APs use a wireless backhaul link to connect to the network where Ethernet cabling is unavailable or impractical.
Question 4: A university wants to support 150 concurrent users per AP in a lecture hall. Which design approach best addresses this high-density scenario?
- Use a single high-power AP mounted at the ceiling center
- Deploy multiple APs with reduced transmit power and use 802.11ac/ax MU-MIMO (Correct answer)
- Install directional antennas pointing outward from the hall
- Use only 2.4 GHz to maximize client compatibility
Correct answer: Deploy multiple APs with reduced transmit power and use 802.11ac/ax MU-MIMO
High-density venues require multiple APs with lower power and technologies like MU-MIMO to serve many simultaneous clients efficiently.
Question 5: What is the primary advantage of using 80 MHz channel width in 802.11ac compared to 40 MHz?
- Better range due to lower frequency
- Higher throughput due to more available spectrum (Correct answer)
- Fewer co-channel interference issues
- Improved battery life for client devices
Correct answer: Higher throughput due to more available spectrum
80 MHz channel width doubles the available spectrum compared to 40 MHz, enabling significantly higher throughput in 802.11ac.
Question 6: During a post-deployment site survey, a technician notices dead zones near elevator shafts. What is the most likely cause?
- Elevator shafts act as RF amplifiers creating interference
- Metal elevator shafts cause significant RF signal attenuation (Correct answer)
- Elevators generate Bluetooth interference that disrupts WLAN
- The APs near elevators are configured on DFS channels
Correct answer: Metal elevator shafts cause significant RF signal attenuation
Metal elevator shafts are highly effective RF shields, absorbing and blocking Wi-Fi signals and creating coverage dead zones nearby.
Question 7: In Aruba's ARM feature, what happens when an AP detects high interference on its current channel?
- The AP disables its radio until interference clears
- ARM automatically switches the AP to a less congested channel (Correct answer)
- The AP increases its transmit power to overcome interference
- ARM notifies the administrator and waits for manual intervention
Correct answer: ARM automatically switches the AP to a less congested channel
Aruba's ARM dynamically reassigns channels when interference is detected, automatically moving APs to cleaner spectrum.
ACMA WLAN Design 3
What is the recommended minimum Received Signal Strength Indicator (RSSI) for a voice over WLAN deployment?