OPTICOM OPERA - V 3.5 User Manual page 153

C H A P T E R 6 : T E L E P H O N Y
T E S T I N G
Figure 6.26: Delay vs. Time diagram
Figure 6.27 shows another view of the delay measurement. The delay
histogram tells you the probability of each delay that actually occurred as the
Probability Distribution Function (PDF). On the y-axis you see the probability in
percent for each delay, whereas on the x-axis you find the delay in ms. The
integral of this function is always 100%. Although the diagram looks like a bar
chart, it is in fact the probability density function of the delay. The bar chart
effect is due to the discrete delay values occurring in the measurement and the
resolution of the algorithm. This diagram together with the Delay vs. Time
diagram defines the full dynamic characteristic of the delay of your system
under test.
Figure 6.27:
PESQ Delay Histogram
The behaviour of e.g. AGC devices can best be measured using the Gain
Variation diagram as shown in
the variable part of the gain in dB, which must be seen relative to the overall
attenuation as shown in the Final Results diagram. The x-axis is the time in ms.
Please note, that both signals must exceed the threshold in quiet by app. 7dB. A
red line will be plotted for the invalid periods. All frames that do not meet this
criterion will be set to 0dB.
B A N D V O I C E
Figure 6.28 . The y-axis of this diagram indicates
147
Q U A L I T Y
Delay Histogram
Gain Variation