CWDP Advanced Site Survey Techniques — Questions and Answers
Question 1: What is the primary purpose of a predictive site survey in WLAN design?
- To model RF coverage and capacity using floor plans before deploying equipment (Correct answer)
- To measure existing wireless signal strength throughout a building
- To test the speed of the current network
- To count the number of client devices on the network
Correct answer: To model RF coverage and capacity using floor plans before deploying equipment
Predictive site surveys use software tools to simulate RF propagation on imported floor plans, allowing designers to plan AP placement, channel assignments, and power levels before any equipment is physically installed.
Question 2: What information should be gathered during a pre-survey site visit?
- Building materials, ceiling heights, existing infrastructure, RF interference sources, and client requirements (Correct answer)
- Only the number of rooms in the building
- The building's electrical consumption data
- Previous tenant's network design documents only
Correct answer: Building materials, ceiling heights, existing infrastructure, RF interference sources, and client requirements
A thorough pre-survey visit documents construction materials (wall composition, glass types), ceiling types and heights, existing cabling and mounting points, potential RF interference sources, aesthetic requirements, and client needs.
Question 3: What is the difference between a passive and active site survey?
- Passive surveys listen to existing RF without associating; active surveys connect to the network and measure performance (Correct answer)
- Passive surveys are done at night; active surveys during business hours
- Passive surveys use fewer tools than active surveys
- There is no difference in the data collected
Correct answer: Passive surveys listen to existing RF without associating; active surveys connect to the network and measure performance
Passive surveys capture RF data (signal strength, noise, interference) without connecting to any network, while active surveys associate with the WLAN and measure actual throughput, latency, packet loss, and roaming behavior.
Question 4: How does RF attenuation differ between 2.4 GHz and 5 GHz when penetrating building materials?
- 5 GHz signals experience greater attenuation through most building materials than 2.4 GHz (Correct answer)
- 2.4 GHz experiences more attenuation than 5 GHz
- Both frequencies attenuate equally through all materials
- Neither frequency is affected by building materials
Correct answer: 5 GHz signals experience greater attenuation through most building materials than 2.4 GHz
Higher frequency signals (5 GHz) experience greater absorption and attenuation when passing through building materials compared to lower frequency signals (2.4 GHz), resulting in shorter effective range.
Question 5: What is a spectrum analysis and when should it be performed during WLAN design?
- An analysis of the RF environment to identify interference sources, performed during the site survey phase (Correct answer)
- A test of the color spectrum of LED indicators on APs
- An analysis performed only after network deployment
- A measurement of visible light interference on wireless signals
Correct answer: An analysis of the RF environment to identify interference sources, performed during the site survey phase
Spectrum analysis identifies sources of RF interference (microwave ovens, Bluetooth, radar, cordless phones) by analyzing the radio frequency spectrum, and should be performed during the site survey to inform AP placement and channel planning.
Question 6: What is the recommended minimum signal-to-noise ratio (SNR) for reliable VoWLAN (Voice over WLAN)?
- 25 dB or higher (Correct answer)
- 10 dB
- 5 dB
- 40 dB
Correct answer: 25 dB or higher
Voice over WLAN requires an SNR of at least 25 dB to maintain call quality, which is higher than the minimum for data applications due to voice's sensitivity to latency, jitter, and packet loss.
CWDP Advanced Site Survey Techniques
What is the primary purpose of a predictive site survey in WLAN design?