CWNA General Information 4 — Questions and Answers
Question 1: What is the minimum System Operating Margin (SOM) typically recommended for a reliable outdoor wireless bridge link?
- 5 dB
- 10 dB (Correct answer)
- 25 dB
- 40 dB
Correct answer: 10 dB
A minimum SOM of 10 dB is generally recommended for outdoor links to account for environmental factors like rain fade and obstructions.
Question 2: Which 802.11 standard first defined operation in the 6 GHz frequency band?
- 802.11ax (Correct answer)
- 802.11ac
- 802.11ad
- 802.11ay
Correct answer: 802.11ax
802.11ax (Wi-Fi 6E) was amended to include operation in the 6 GHz band, providing access to up to 1.2 GHz of additional spectrum in the US.
Question 3: What is the role of the Distribution System (DS) in an 802.11 ESS?
- It is the wireless medium connecting clients to APs
- It is the wired backbone interconnecting multiple APs (Correct answer)
- It manages roaming decisions for client stations
- It encrypts traffic between the BSS and the internet
Correct answer: It is the wired backbone interconnecting multiple APs
The Distribution System is typically an Ethernet backbone that interconnects multiple APs, enabling stations to roam across the ESS.
Question 4: In 802.11 power management, what term describes the buffering of frames by an AP for sleeping client stations?
- Power Save Poll (PS-Poll)
- Traffic Indication Map (TIM) (Correct answer)
- Delivery Traffic Indication Message (DTIM)
- Unscheduled Automatic Power Save Delivery (U-APSD)
Correct answer: Traffic Indication Map (TIM)
The TIM information element in beacon frames indicates which sleeping stations have buffered unicast frames waiting at the AP.
Question 5: What does the Fresnel Zone concept determine in outdoor wireless link planning?
- The maximum transmission power allowed for a link
- The volume of space around the LOS path that must remain clear of obstructions (Correct answer)
- The minimum antenna height required by FCC regulations
- The channel width needed for a given data rate
Correct answer: The volume of space around the LOS path that must remain clear of obstructions
The Fresnel Zone is an ellipsoidal region around the line-of-sight path; obstructions within this zone (especially the first zone) cause significant signal diffraction and loss.
Question 6: Which CWNA exam topic area specifically addresses site survey methodologies and RF coverage validation?
- WLAN Troubleshooting and Design (Correct answer)
- 802.11 Protocol and Layer 2
- WLAN Network Architecture
- RF Technologies and Antenna Concepts
Correct answer: WLAN Troubleshooting and Design
WLAN Troubleshooting and Design covers passive and active site survey methods, predictive surveys, and validating RF coverage post-deployment.
Question 7: What is the key difference between a 'passive' and an 'active' wireless site survey?
- Passive surveys use APs; active surveys use spectrum analyzers only
- Passive surveys only listen to existing RF; active surveys associate to APs and measure throughput (Correct answer)
- Active surveys measure RF with the WLAN off; passive surveys require live APs
- Passive surveys are done indoors; active surveys are done outdoors only
Correct answer: Passive surveys only listen to existing RF; active surveys associate to APs and measure throughput
A passive survey captures and analyzes RF signals without associating to any network, while an active survey associates to APs and measures real throughput and latency.
CWNA General Information 4
What is the minimum System Operating Margin (SOM) typically recommended for a reliable outdoor wireless bridge link?