Channel Analysis tab

The channel analysis tab provides various visualisations to complement the information you can find in the spectrum tab. In this tab you find three types of widget, all of which can be toggled on and off using the checkboxes in the toolbar at the top of the tab:

• Energy Density plot. This is a visualisation of the energy density of the 2.4 GHz spectrum. A probability density plot can also be toggled on, as can a WiFi interference overlay if WiFi capture was enabled in the capture setting.
• Channel Utilisation and Throughput histograms
• Channel Map visualisations

Please note that as these graphs are designed to complement the spectrum tab, the spectrum tab must be open and selected for the information in the channel analysis tab to update. All of the graphs in the channel analysis tab will show you information based on the time interval currently selected in the spectrum tab's throughput plot, and any filters that you have applied.

Navigating the tab

To open the tab, navigate to "View" and select "Channel Analysis."

All plots in the tab can be toggled on or off using the checkboxes in the toolbar at the top of the tab. This includes any subplots, like the Signal Distribution and WiFi Interference options which are part of the energy density widget.

Any individual widget (except the channel map widgets which are fixed size) can be resized vertically by clicking and dragging the grey separator at its base. They may also be reordered, either by clicking anywhere in the widget and dragging it above or below another widget, or by right-clicking and selecting either "Move to Top" or "Move to Bottom."

Energy density plot

This graph relies on spectrum data, so will only appear in the channel analysis tab in captures where the spectrum has been enabled in the capture settings.

The plot is divided into the same 79 channels of the 2.4 GHz spectrum used in Bluetooth Classic, and shows the noise heard by the sniffer in the currently selected spectrum time frame. Hovering over any of the channels shows a tooltip which gives the minimum, maximum, mean, 25th percentile, and 75th percentile signal seen in that channel. The blue region represents the floor to the 25th percentile, the grey region represents the 25th to the 75th percentile, and the red region represents the 75th percentile to the peak signal. The solid red line is the signal mean.

In the top left of the plot is shown the min-max range of attenuation applied during the selected time window.

Signal distribution plot

Toggling on the signal distribution checkbox shows a probability density graph which shares the y axis with the energy density graph. Hovering the cursor over this plot will show a tooltip that gives the percentage of observations at that noise level. This percentage is simply 100x times the probability shown on the x axis.

WiFi interference

If WiFi was selected in the capture settings, then the option to overlay a WiFi interference visualisation on the energy density plot will be available.

This shows the distribution of WiFi packets in the spectrum, and the percentage airtime taken up by WiFi per channel. Note the separate y axis on the right hand side of the plot.

Channel utilisation and throughput histograms

The channel utilisation and throughput plots show histograms for each PHY channel (79 for Classic, 40 for LE).

The channel utilisation plot shows the number of packets seen per channel, and shows in different colours the state of those packets; whether they were transmitted correctly, retransmitted, CRC fail etc. The channel health statistic is simply the percentage of OK packets for that channel. It is displayed as green for channel health above 90%, and red for below 50%.

The channel throughput graph shows the throughput in bytes per channel.

Channel map visualisations

Each box represents a channel in the 2.4 GHz range, 79 for Classic and 40 for LE. The various colours indicate the current state of the channel map, with each permutation of central/peripheral report accounted for. For LE, the primary advertising channels are greyed out. Hovering over a particular channel will show a tooltip with extra information, including the addresses of the central and peripheral, and the start time and packet number of the channel map update packet.

Hashed boxes indicate a change of state for that channel from the previous update. This information, if applicable, will also appear in the tooltip for relevant channels.

The visualisations show the latest channel map updates seen for that connection/broadcast in the spectrum time frame currently selected. If there is no channel map update information available in the time frame selected, then no information will be shown.

You are able to select up to four connections/broadcasts to view simultaneously, if they are available, by selecting them in the Select Connections/Select Broadcasts dropdown menu. If there are more than 5 available connections with your current filters applied, then a MAC address search box will be available.