The AP has been configured property for a VoWLAN survey The RF environment contains a noise of -87 to -90 dBm. What is the target value for the cell edge reading?
A. -62 dBm
B. -67 dBm
C. -60 dBm
D. -70 dBm
What is the target value for the cell edge reading?
It is correct. A.
X- (-85 Actual SNR)= 25 (ideal SNR)
x= -62
https://www.cisco.com/c/en/us/td/docs/wireless/technology/vowlan/troubleshooting/vowlan_troubleshoot/8_Site_Survey_RF_Design_Valid.html
The problem is that Cisco documentation states -67dBm, an SNR of 25 but also that the noise floor should not exceed -92dBM, so mathematically the answer should be -62dBm when subtracting the noise level from -67dBm, but I’m afraid in this case, the answer should be -67dBm and the source of the high noise floor be investigated. This question example of a horrible question used to trip up even folks that fully understand the subject matter.
Correction when subtracting the noise I floor from the SNR.
@Benoit: Kudos!
Noting to add
@john: you can not understand Benoit at all
It should be A
I fully understand what you are saying Benoit, but I think the magic answer is B.
Answer is B
My opinion: The required RSSI is indeed -67 dBm, however, there is a second requirement of having minimum 25 db SNR.
from this document: https://www.cisco.com/c/en/us/support/docs/wireless/5500-series-wireless-controllers/116057-site-survey-guidelines-wlan-00.html
“To accommodate the requirement to support wireless Voice over IP (VoIP), refer to the RF guidelines specified in the Cisco 7925G Wireless IP Phone Deployment Guide. The minimum recommended wireless signal strength for voice applications is -67 dBm and the minimum SNR is 25 dB.”
so, If the noise level goes up to -87dBm, the signal should be no weaker than 87-25 = 62dBm to have an SNR of 25 dB, or am I wrong here?
so, my guess would be answer A
comments are welcome 😉
The correct answer is “B”