Information About Spectrum Analysis
Cisco DNA Center receives a spectrogram stream from access points and visualizes spectrum analysis as a real-time spectrogram view. Network administrators receive RF violation issues from end users or radio frequency issue from the Cisco DNA Center. To analyze a violation, you should select the corresponding AP and analyze the spectrogram stream.
Based on whether a setting is global or is meant for a specific channel, every AP uses a specific channel to communicate with clients.
When a lot of clients join on the same AP, there is a high possibility of frames getting dropped off. When there is an issue of clients dropping quickly, or not getting onboarded, you should perform the spectrum analysis to check if the channels are clogged.
You can enable spectrum analysis on every AP listed in the web UI and view the graphs based on the corresponding AP. When enabled, the APs send spectrum data to Cisco DNA Centre which then aggregates it into 3 distinct charts.
You can view the following charts while performing a spectrum analysis:
Persistance Charts: Plot the amplitude-to-power ratio of each signal at each channel for a period of five minutes. The chart is color coded with blue color representing one signal and red representing many signals. This chart also plots the opacity that represents the age of the signal data within the five minute interval, with older data being more transparent.
Waterfall Charts: Plot all the signals that are analyzed in the channel for a period of five minutes with intensity on X axis, and with time represented in the Y axis. The chart is color coded, with blue color representing a low value and red representing a high value.
Interference and Duty Charts: Plot the severity of detected interference for each channel band, and list the interference type. Interference is plotted as a circle, where the center represents the severity, and the radius represents the section of the channel band that is affected. The impact of the interference is measured as severity, with values ranging from 0 to 100. The interference type is determined from RF signature identified by Cisco CleanAir technology of the interference.