User guide

45 Mbps Backhaul User Guide
Issue 3, December 2004 Page 59 of 113
Statistics Window. DFS uses statistical analysis to process the received peak and mean measurement. The
statistical analysis is based around a fixed measurement quantization period. The default quantization period is
one minute. DFS collects data for the specified quantization period and only at the end of that period is the
statistical analysis performed. Increasing the measurement quantization period will reduce the dynamic response
time of the algorithm but increase the statistical significance of the metrics. (Default 1 minute). Displaying and
making decisions based on one minutes worth of data would make DFS very dynamic. Therefore the Statistics
Window attribute allows the user to concatenate quantization periods before making the assessment of the
prevailing interference environment. This allows the algorithms to bias away from any channel that has
detected interference during the period of the statistics window and slow the channel hopping dynamics down.
It also has the effect of biasing away from localized impulsive interference sources.
Interference Threshold. DFS uses the interference threshold to perform instantaneous channel hops. If the
measured interference on a channel exceeds the specified threshold then DFS will instruct wireless immediately
search for a better channel. If a better channel cannot be found then 45 Mbps Backhaul will continue to use the
current active channel. (Default –85 dBm)
6.3.5.6 Barring Channels
Channels can only be barred!/!unbarred by the system administrator from the master DFS webpage. The
barring!/!unbarring operations are disabled on the slave webpage. If an attempt to bar!/!unbar a channel is made
at the slave a warning dialog is generated.
Barring!/!Unbarring of channels is performed by clicking the appropriate channel on the local or peer channel
spectrum plots on the master webpage. Each bar!/!unbar attempt will be proceeded by a conformation dialog. It
should be noted that the channel bar will take effect immediately and is not related to the measurement
quantization period.
6.3.5.7 Local and Peer Channel Spectrum Graphics
Spectrum Management presents its computed statistical measurements in a graphical display on both the master
and slave DFS webpage.
Figure 28 Example Spectrum Management Graphic
The X-axis shows a stylized view of the 19 selectable wireless channels. It is important to note that adjacent
channels on the display have a 5 MHz overlap. The display separates the display of channels to help the clarity
of the resultant display. The axis is labeled using the channel center frequencies in MHz.
The Y-axis shows the interference power levels from –100 to –40 dBm.
The active channel (channel 1 in Figure 28) is always marked using hatched green and white lines. The width of
the hatching is directly proportional the 11 MHz spectral occupancy of the channel.
The individual channel metrics are displayed using a colored bar, an ‘I’ bar and a peak symbol.
The colored bar represents the following channel state: