An Upstream Spectrum Session displays collected data in the form of a heat map. The heat map is graphical representation of your upstream spectrum data, utilizing colors to indicate the rate at which a particular frequency and power density is recorded during the session. The heat map helps visualize normal patterns or trouble spots.
The color scale on the right of the map correlates the number of occurrences (Count). Two vertical lines indicate your selected channel. In the image above, you can see five channels. In this session, the heat map indicates that the SC-QAM channel centered around 14.2 MHz, and the OFDMA channel between 28.5 and 38.5 MHz are the most active (see the red band). Analysis also indicates normal operations.
You can manipulate your data and graph display with the controls across the top of the graph.
- Download to CSV — Click this icon to export your heat map data to a CSV file.
- Switch to On-Demand — Enabled for completed sessions only, click this phrase to initiate an active capture.
- Zoom Last and Zoom icon — Use to zoom in the display of your
heat map.
The following image is zoomed in on the OFDMA channel.
- Peak Hold — Turn on or off to highlight the highest power density value at each frequency.
- Average — Turn on or off to indicate the average power
density at each frequency.
The following image shows the Peak Hold (green line) and Average (purple line).
- Create a new Upstream Spectrum Session (+) — For completed sessions, click to create a new session. The dialog box is populated with the setting of the current session.
- Stop the session — For active sessions only, click the stop icon to stop the current Upstream Spectrum Session. Once stopped, you cannot restart a session.
You can expand the bottom panel to see the session parameters, and to manipulate values for X-Axis, Y-Axis, Floor Value and Ceiling Value. You can click Reset to return to values that are automatically selected to best match the data. Altering floor and ceiling settings allows you to filter out noise and concentrate on specific power ranges.
The following image display an instance where sweeping noise is detected on an idle channel. During this session, Compatibility mode is selected, and the Service Identifier is IdleFFT.
The area highlighted indicates the presence of noise, on what should be an idle channel. Because the color is blue, it indicates that the noise is not constant.