Bird Technologies 7022-Manual - Manual (Page 19)

7
Statistical Power
Most modern wireless communication systems employ com-
plex modulation methods like orthogonal frequency division
multiplexing (OFDM) or Quadrature Amplitude Modulation
(QAM). These methods use a combination amplitude, fre-
quency, or phase to create symbol based multichannel or
multi-carrier systems that result in pseudorandom or noise-
like power envelops. The peak-to-average power ratio of such
a waveform can be a complex function of the data stream
content rather than just amplitude. Since digitally modulated
signals often appear noise-like, statistical analysis may be
used in order to characterize them.
The Statistical Power Sensor collects samples of the envelope
of a carrier and accumulates them in a series of bins. This
information is useful for qualitative assessment of complex
waveforms that have a finite number of discrete amplitude
levels, like QAM.
A more useful measurement is one that shows how often var-
ious power levels occur as a percentage of data ensemble
length. This is done by calculating the cumulative distribution
function (CDF) from the PDF.

CDF - Shows the probability in percent that the mea-
sured power is less than or equal to a specified
power level.

Complementary CDF (CCDF) - The probability that
the measured power is greater than a specified
power level.

Crest Factor - Peak-to-average ratio, or Crest Factor,
displays the number of samples analyzed, elapsed
time, and confidence band.