Interference and Noise threshold for 802.11 b/g/n and 802.11 a/c interface of an AP

[Khundmir4cisco]

Dear Expert,

We have Prime and we are monitoring wireless. We are receiving a huge number of alarms from WLC regarding the interference and Noise threshold alarms. I have searched about setting up threshold and could only find an article which says that the interference threshold can be set up from 0-100. My worry is to how to chose the best value or optimum value. 

https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-1/mobility_express/b_RRM_White_Paper/b_RRM_White_Paper_chapter_010.html

In the above link there is no mention about the optimum value. is there any formulae for chosing the optimum value. On what parameters it depend and how to chose the best value using best practice. 

Thank you. 

[Andrew Khalil]

Dear Khundmir4cisco,

Greetings,

I guess, no one would answer this question for you better than you! 

But you need first to understand some definitions, then you will answer yourself! 

first, I would like to define a term "Signal to Noise Ratio" SNR, which is not actually a ratio, but in fact it is the difference between the received signal by the client and the noise floor!, data corruption and therefore re-transmissions will occur if the received signal is too close to the noise floor which is causing throughput and latency.

SNR is a better way to judge the quality of signal because it also takes the noise floor or ambient noise of the RF environment into account.  For instance, a received signal of -65 dBm can be considered good at location that has a noise floor of -90 dBm (SNR 25 dB) but not so much at a location with a noise floor of -80 dBm (SNR 15 dB).

Generally, a signal with an SNR value of 20 dB or more is recommended for data networks where as an SNR value of 25 dB or more is recommended for networks that use voice applications.

I think, you need to define your environment noise floor and your AP signal, and according to that will know what value you need to setup! 

I hope my reply is helpful enough to get a rating, also please don't forget to mark it as a solution if it helped you to solve your issue! 

Bst Rgds,

Andrew Khalil