Features
User Manual for AZ430 WAN Satellite Modem
6.3.6
Channel quality estimation
The channel quality estimation displays the Es/No of the modulated symbols for
each of the DVB-S2 streams in the received carrier. It differs from the total carrier
Es/No which only looks at the Physical Layer Headers (which are modulated in a
kind of BPSK modulation). Hence in a non-linear channel the total carrier Es/No
and Channel Quality Estimation will differ because symbols modulated with higher
modulation and coding than the headers will suffer more from the degradation due
to non-linearity. It is to be noted that the Es/No indication is derived from the
number of corrections the LDPC decoder had to perform. Hence it is most accurate
close to the threshold of decoding. For high Es/No values the error becomes
larger.
6.3.7 C/D
est.
Carrier-to-distortion estimation. This value (in dB) is a measure for the distortion
due to linear and non-linear degradation that is present in each of the DVB-S2
streams in the received carrier. It can be used to determine the optimal operating
point when optimising a (new) satellite link (for example input back off). The
operation point should be selected to have the highest C/D value.
6.3.8 C/D
clipping
The C/D clipping will indicate “<” or “>” when the C/D value is too low or too high to
be accurately determined. In case it is too low, the link margin might be too low in
order for the detector to operate correctly. In case it is too high, there might not be
enough distortion (for example in perfectly linear operation) in order for the detector
to display a meaningful value.
6.3.9
Link margin est.
Link margin estimation for each of the DVB-S2 streams in the received carrier. This
monitoring parameter indicates how much the Es/No is above the decoding
threshold. It is a measure for the number of dBs of fading that is possible on the
link before the demodulator is not able to decode the received signal anymore.
6.3.10 Link margin clipping
The link margin clipping will indicate “<” or “>” when the link margin value is too low
or too high to be accurately determined. In case it is too low, the link margin might
be too low in order for the detector to operate correctly. In case it is too high, there
might not be enough decoding errors (for example in channel with high link margin)
in order for the detector to display a meaningful value.
version 1.0
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SHAPING THE FUTURE OF SATELLITE COMMUNICATIONS
