User Guide: PTP 600 Series
Managing spectrum
phn-0896_012v000
Jul 2010
7-29
Key metrics
The ‘I’ bar and top of the coloured bar represent three key metrics (
Table 7-8
). The
vertical part of the ‘I’ bar represents the statistical spread between the peak and the
mean of the statistical distribution.
Table 7-8 Key metrics represented in the spectrum management plot
Metric
Description
How
represented
Peak of Means
The largest mean interference measurement
encountered during the quantization period.
The peak of means is useful for detecting
slightly longer duration spikes in the
interference environment.
Upper horizontal
bar.
Mean of Means
The arithmetic mean 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 at predicting intermittent
interference and is included to show the
spread between the Mean of Means, the
99.9% Percentile and the Peak of Means.
Lower horizontal
bar.
99.9%
Percentile of
the Means
The value of mean interference measurement
which 99.9% of all mean measurements fall
below, during the quantization period. The
99.9% percentile metric is useful for
detecting short duration repetitive
interference that by its very nature has a
minimal effect of the mean of means.
Top of the colored
bar.
NOTE
The arithmetic mean is the true power mean and not the mean of the values
expressed in dBm.
Spectrum Management uses the 99.9% Percentile as the prime interference
measurement. All subsequent references to interference level refer to this
percentile measurement.
4Gon www.4Gon.co.uk info@4gon.co.uk Tel: +44 (0)1245 808195 Fax: +44 (0)1245 808299