CWS Site Survey Fundamentals Flashcards

A company is planning a Wi-Fi deployment in a new office building that is currently an empty shell with no physical infrastructure installed. They want to create an initial AP placement plan and get a budgetary quote for hardware. Which type of site survey is most appropriate at this stage?

Answer: Predictive survey

A predictive survey is the correct choice because it uses software to model the RF environment based on floor plans and building material properties. This allows for initial planning and estimation without needing physical access or active hardware, which is ideal for a building that is not yet built out.

During a validation survey, a technician measures a consistent RSSI of -67 dBm in a conference room. The noise floor in the same area is measured at -92 dBm. What is the Signal-to-Noise Ratio (SNR) for this location?

Answer: 25 dB

The Signal-to-Noise Ratio (SNR) is calculated by subtracting the noise floor from the Received Signal Strength Indication (RSSI). In this case, the calculation is (-67 dBm) - (-92 dBm) = 25 dB. A higher SNR value indicates a cleaner, more reliable signal.

A technician performing a site survey in an office breakroom notices significant, wideband RF interference across the entire 2.4 GHz band every day around lunchtime. This interference is not present on the 5 GHz band. Which of the following is the MOST likely source of this non-Wi-Fi interference?

Answer: Microwave oven

Microwave ovens are a well-known source of powerful, broadband interference in the 2.4 GHz frequency band. The timing of the interference around lunchtime is a strong indicator that this is the cause. Bluetooth is typically low-power and frequency-hopping, while adjacent and co-channel interference are Wi-Fi specific issues.

A network engineer needs to troubleshoot a Wi-Fi performance issue in a manufacturing facility. It is suspected that machinery is emitting RF energy that disrupts the wireless network. What is the best tool to visualize ALL RF activity, including Wi-Fi and non-Wi-Fi sources, across the frequency spectrum?

Answer: A spectrum analyzer

A spectrum analyzer is specifically designed to measure and display the magnitude of RF energy across a range of frequencies. This allows it to visualize signals from both Wi-Fi (802.11) and non-Wi-Fi sources like machinery, providing a complete picture of the RF environment essential for troubleshooting interference.

Before starting a physical walk-through with site survey software, what is the most critical first step to ensure the accuracy of the collected data points on the floor plan?

Answer: Calibrate the map by defining the distance between two known points.

Calibrating the map is a fundamental step that sets the scale of the floor plan within the survey software. By measuring a real-world distance (like a long hallway) and inputting that value between two points on the map, the software can accurately place the collected RF data. Without proper calibration, the resulting heatmaps will be distorted and useless for AP placement decisions.

A post-deployment survey in a high-density office reveals an area where two APs, both configured on channel 36 in the 5 GHz band, provide coverage with a strong RSSI of -60 dBm each. Users in this overlap area report poor performance and frequent connection issues. This issue is an example of what?

Answer: Co-Channel Interference (CCI)

Co-Channel Interference (CCI), also known as co-channel contention, occurs when multiple access points on the same channel are close enough to hear each other's transmissions. This forces them and their clients to contend for the same airtime, increasing wait times and degrading performance, even with strong signal strength.