User guide

45 Mbps Backhaul User Guide
Issue 3, December 2004 Page 56 of 113
Mean of Means is the arithmetic mean
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of the measured means during a quantization period. The mean of
means is a coarse measure of signal interference and gives an indication of the average interference level
measured during the quantization period. The metric is not very good and predicting intermittent interference
and is included to show the spread between the mean of means, the 99.9% percentile and the peak of means.
Important Note. f DFS uses the 99.9% percentile as the prime interference measurement. All subsequent
references to interference level refer to this percentile measurement.
The display of statistical measurement on the spectrum management page always shows a statistical summary
of all channel measurement. The statistical summary is controlled by the Statistics Window attribute. This
attribute defaults to a value of twenty minutes, which means that the mean and percentile values displayed for
each channel are calculated over the 20 minute period. All channel decisions are made using the values
computed over the statistics window period.
6.3.5.4 The Spectrum Management Master / Slave Relationship
By default Spectrum Management operates in a master / slave relationship. The master is assumed to be the link
master configured during installation. All Spectrum Management configuration changes MUST be performed
from the master, to enforce this the Spectrum Management webpage has a different appearance depending if
you are viewing the data from the master or slave.
All configuration changes are applied at the master only. All configuration changes are messaged from the
master to the slave. Any Spectrum Management configuration messages received at the slave are stored in non-
volatile memory. This enables both master and slave to keep identical copies of Spectrum Management
configuration data in their non-volatile memories. It is therefore possible to swap master and slave roles on an
active Point-to-Point link without modifying Spectrum Management configuration.
Figure 26 shows an example Spectrum Management webpage as seen from the master. Figure 27 shows an
example Spectrum Management webpage as seen from the slave. It should be noted that not all the key
Spectrum Management configuration attributes are available on the slave webpage.
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The arithmetic mean is the true power mean and not the mean of the values expressed in dBm.