Features
User Manual for AZ430 WAN Satellite Modem
It is commonly accepted that a transmission is considered as error-free when the
PER (Packet Error Rate) at the reception side is below 10
-7
. For each DVB-S2
modcod, as shown in Figure 14, a minimum value (Es/No)
QEF
guarantees quasi
error free transmission.
Figure 15 - LME – Linear Environment
In a linear environment, as described in Figure 15, the Link Margin Estimates
(LME) provided with or without NoDE are identical. They correspond with the
difference between the channel Es/No and the (Es/no)
QEF
of the corresponding
modcod, which is the real operation margin of the transmission.
Figure 16 - LME – Non-Linear Environment
When non-linear distortion is present, the real link margin is decreased and is no
longer equal to the difference between the measured Es/No value and (Es/No)
QEF
.
NoDE calculates the amount of distortion present on the received signal, then
corrects the minimum ES/No value to obtain quasi error-free transmission by a delta
Δ
that takes into account the effect of the distortion. In a non-linear environment, as
described in Figure 16, NoDE enables the measurement of an accurate Link
Margin Estimation. By providing the operator with an accurate estimation of the
Real Link Margin, NoDE prevents the link being operated in a region where the
performance is unpredictable and only marginally stable.
version 1.0
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SHAPING THE FUTURE OF SATELLITE COMMUNICATIONS
