CWNP CWDP Wi-Fi Design CWDP-305 Question # 43 Topic 5 Discussion

To determine the minimum RSSI required for a VoWLAN deployment with a specified SNR, use the formula:

Minimum RSSI = Noise Floor + Required SNR

Given:

Required SNR = 25 dB

Noise Floor = -88 dBm

Calculation:

Minimum RSSI = -88 dBm + 25 dB = -63 dBm

Thus, the minimum RSSI needed is -63 dBm.

Explanation with Extract:

Per the *CWDP-305 Study Guide*, Voice over WLAN (VoWLAN) deployments require robust signal quality. The SNR is critical for voice performance, and the guide specifies:

"For VoWLAN, an SNR of 25 dB is typically required to ensure clear voice quality and minimal latency."

"The minimum RSSI is derived by adding the required SNR value to the measured noise floor."

This aligns with RF fundamentals where SNR is the difference between the received signal strength (RSSI) and the ambient noise floor. A higher SNR (e.g., 25 dB for voice) demands a stronger signal relative to noise. Here, a noise floor of -88 dBm plus 25 dB SNR results in -63 dBm RSSI (Option D).

Why other options fail:

A. -70 dBm: Results in 18 dB SNR (−70 − (−88) = 18 dB), insufficient for VoWLAN.

B. -67 dBm: Yields 21 dB SNR (−67 − (−88) = 21 dB), below the 25 dB requirement.

C. -65 dBm: Provides 23 dB SNR (−65 − (−88) = 23 dB), still inadequate.