CWNA WLAN Design & Site Survey 1 — Questions and Answers
Question 1: What type of site survey involves walking through a facility to assess RF coverage without associating to any access point?
- Active survey
- Passive survey (Correct answer)
- Predictive survey
- Validation survey
Correct answer: Passive survey
A passive survey captures existing RF signals by listening only, without associating to an AP, making it ideal for assessing the existing RF environment.
Question 2: What is the primary purpose of a predictive site survey?
- To measure actual RF coverage after AP deployment
- To model WLAN coverage using floor plan software before deployment (Correct answer)
- To test client roaming between APs
- To measure co-channel interference in a live network
Correct answer: To model WLAN coverage using floor plan software before deployment
Predictive surveys use specialized software to model expected RF coverage from proposed AP placements on a floor plan before any hardware is installed.
Question 3: Which tool is best suited for identifying non-802.11 RF interference sources such as microwave ovens or DECT phones during a site survey?
- Wi-Fi protocol analyzer
- Spectrum analyzer (Correct answer)
- Network management system
- Packet sniffer
Correct answer: Spectrum analyzer
A spectrum analyzer can detect and identify non-802.11 RF energy sources across a frequency range, which protocol analyzers cannot do since they only decode 802.11 frames.
Question 4: What is the recommended minimum RSSI for supporting Voice over Wi-Fi (VoWiFi) applications?
- -50 dBm
- -67 dBm (Correct answer)
- -75 dBm
- -85 dBm
Correct answer: -67 dBm
Voice over Wi-Fi applications typically require a minimum RSSI of -67 dBm to maintain the consistent signal quality needed for real-time voice communications.
Question 5: In WLAN design, what does 'cell overlap' refer to?
- The dead zone between two APs where neither signal is usable
- The area where the coverage zones of two or more APs intersect (Correct answer)
- The region beyond an AP's maximum coverage boundary
- The interference zone directly around an AP antenna
Correct answer: The area where the coverage zones of two or more APs intersect
Cell overlap is the intentional area where signals from adjacent APs intersect, which is required so that roaming clients can detect the next AP before losing the current one.
Question 6: What percentage of cell overlap is generally recommended between adjacent APs to support seamless roaming for data applications?
- 5-10%
- 15-20% (Correct answer)
- 35-45%
- 55-65%
Correct answer: 15-20%
A 15-20% cell overlap provides sufficient coverage continuity for clients to detect and initiate roaming to the next AP before the current signal becomes unusable.
Question 7: What is the purpose of measuring the 'noise floor' during a site survey?
- To determine the maximum AP transmit power allowed by regulation
- To establish the baseline RF interference level present in the environment (Correct answer)
- To measure the AP antenna gain at various angles
- To calculate the maximum number of clients per AP
Correct answer: To establish the baseline RF interference level present in the environment
Measuring the noise floor establishes the baseline level of ambient RF interference in the environment, which is essential for calculating signal-to-noise ratio requirements.
CWNA WLAN Design & Site Survey 1
What type of site survey involves walking through a facility to assess RF coverage without associating to any access point?