User's Manual

Parameter Description
X-Axis Select either Channel or Frequency to show FFT power for a range of channels or
frequencies. If you select Frequency, you must select the radio frequency on which this chart
should center, and determine the span of frequencies for the graph.
Channel
Range
If you selected Channel in the X-Axis parameter, you must also specify a channel range to
determine which channels appear in the X-axis of this chart. Click the first drop-down list to
select the lowest channel in the range, then click the second drop-down list to select the
highest channel to appear in the chart.
NOTE: This parameter is not configurable for graphs created by hybrid APs.
Center
Frequency
If you selected Frequency in the X-Axis parameter, enter the frequency, in MHz, that you
want to appear in the center of the x-axis of this chart.
Span If you selected Frequency in the X-Axis parameter, specify the size of the range of
frequencies around the selected center frequency. If you set a frequency span of 100 MHz,
for example, the chart shows the FFT duty cycle for a range of frequencies from 50MHz lower
to 50 MHz higher than the selected center.
Y-axis Select the range of power levels, in -dBm, to appear in the y-axis of this chart. Enter the lower
value in the right field, and the higher value in the left field.
Show Select the checkbox by the following items to display that information on the FFT Power chart.
l Average: the average power level of all samples recorded during the last 10 sweeps.
l Maxthe The highest power recorded during the last 10 channel sweeps.
l Max Hold: the highest maximum power level recorded since the chart data was reset. To
clear this setting, click the down arrow at the end of the title bar for this graph and select
Clear Max Hold.
Swept Spectrogram
A spectrogram is a chart that shows how the density of the quantity being plotted varies with time. The
spectrum analysis Swept Spectrogram chart plots real-time FFT Maximums, real-time FFT Averages, or the FFT
Duty Cycle. In this swept spectrogram, the x-axis represents frequency or channel and the y-axis represents
time. Each line in the swept spectrogram corresponds to the data displayed in the Real-Time FFT or FFT Duty
Cycle chart.
This chart is not available for W-AP68 access points. A hybrid AP on a 20 MHz channel will see 40 MHz Wi-Fi data as
non-Wi-Fi data.
The power or duty cycle values recorded in each sweep are mapped to a range of colors. In the average or
maximum FFT power Swept Spectrogram charts, the signal strength levels are indicated by a range of colors
between dark blue, which represents -90 dBm, and red, which represents a higher -50 dBm. The duty cycle
Swept Spectrogram chart shows the percentage of the time tick interval that the selected channel or frequency
was broadcasting a signal. These percentages are indicated by a range of colors between dark blue, which
represents a duty cycle of 0% percent, and red, which represents a duty cycle of 100%.
A spectrogram plot is a complex chart that can display a lot of information. If you are not familiar with these
types of charts, they may be difficult to interpret. The following illustrations can help explain how FFT power
data is rendered in a spectrogram format.
The example in Figure 121 shows how an FFT Power chart could appear if a single data measurement was
plotted as a simple line graph.
Dell Networking W-Series ArubaOS 6.4.x | User Guide Spectrum Analysis | 736