CWNA WLAN Design & Site Survey 2 — Questions and Answers
Question 1: What is 'throughput testing' in the context of a WLAN site survey?
- Testing physical cable connections between APs and switches
- Measuring actual data transfer rates at various locations throughout the facility (Correct answer)
- Analyzing the total number of APs visible from each location
- Measuring signal strength with a handheld RSSI meter
Correct answer: Measuring actual data transfer rates at various locations throughout the facility
Throughput testing measures real data transfer rates at various locations to verify that the WLAN meets the bandwidth requirements of the intended applications.
Question 2: Which best describes the key difference between coverage-based and capacity-based WLAN design?
- Coverage-based focuses on geographic area coverage; capacity-based focuses on number of concurrent users and bandwidth (Correct answer)
- Coverage-based uses fewer, more powerful APs; capacity-based uses cheaper, lower-power APs
- Coverage-based is for indoor deployments; capacity-based is for outdoor deployments
- Coverage-based uses omnidirectional antennas; capacity-based uses only directional antennas
Correct answer: Coverage-based focuses on geographic area coverage; capacity-based focuses on number of concurrent users and bandwidth
Coverage-based design ensures RF signals reach all areas, while capacity-based design accounts for the density of concurrent users and their collective bandwidth demands.
Question 3: In a high-density WLAN deployment, what technique is most effective at reducing co-channel interference?
- Increasing AP transmit power to maximum
- Reducing AP transmit power and deploying more APs with smaller cells (Correct answer)
- Using only the 2.4 GHz band for all clients
- Increasing antenna gain on each AP
Correct answer: Reducing AP transmit power and deploying more APs with smaller cells
Reducing transmit power and deploying more APs creates smaller cells, allowing the same channels to be reused at shorter distances and reducing co-channel interference.
Question 4: Why is Signal-to-Noise Ratio (SNR) more meaningful than RSSI alone when evaluating WLAN performance?
- SNR determines the number of APs required per floor
- SNR indicates the difference between the signal and the noise floor, directly affecting achievable data rates (Correct answer)
- SNR measures the AP's maximum output power in dBm
- SNR defines the channel width that the AP will use
Correct answer: SNR indicates the difference between the signal and the noise floor, directly affecting achievable data rates
SNR measures how much stronger the desired signal is compared to ambient noise; a high SNR enables higher modulation rates and throughput, regardless of the absolute RSSI value.
Question 5: Which set of elements should be included in a thorough site survey report?
- AP placement locations only
- AP placement, channel assignments, transmit power levels, coverage maps, and identified interference sources (Correct answer)
- Coverage maps and interference sources only
- AP serial numbers and firmware versions only
Correct answer: AP placement, channel assignments, transmit power levels, coverage maps, and identified interference sources
A comprehensive site survey report must document AP placement, channel plan, transmit power settings, coverage heat maps, and all identified RF interference sources to provide a complete picture.
Question 6: What is 'adjacent channel interference' in the 2.4 GHz band?
- Interference between APs using channels that are far apart in frequency
- Interference between APs using channels that share overlapping frequency spectrum (Correct answer)
- Interference originating from non-Wi-Fi devices such as Bluetooth
- Interference caused by multipath signal reflections indoors
Correct answer: Interference between APs using channels that share overlapping frequency spectrum
Adjacent channel interference occurs when APs use channels that overlap in frequency; in 2.4 GHz, only channels 1, 6, and 11 are truly non-overlapping in the US.
Question 7: What factor primarily drives the number of APs required in a capacity-based WLAN design?
- The total physical square footage of the building
- The number of concurrent users and their aggregate bandwidth requirements (Correct answer)
- The type and gain of antennas selected for the deployment
- The maximum EIRP permitted by FCC regulations
Correct answer: The number of concurrent users and their aggregate bandwidth requirements
Capacity-based design is driven by how many devices must be supported simultaneously and what bandwidth each requires, which dictates how many APs are needed to avoid overloading any single radio.
CWNA WLAN Design & Site Survey 2
What is 'throughput testing' in the context of a WLAN site survey?