SHAPING THE FUTURE OF SATELLITE COMMUNICATIONS
9.4.6 Data EsNo clipping info
Data EsNo clipping info indicates a clipped link margin.
When reading saturated values for the Es/No estimation, the clipping info will
identify the direction of saturation or return equal if the value is within range.
An asterisk indicates the readout of the Es/No value is about to saturate and may
be not very accurate. "<" or ">" indicates when the EsNo is too low or too high to
be accurately determined.
9.4.7 Data EsNo est
Data EsNo est: Signal to noise estimation.
9.4.8 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.
9.4.9 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.
9.4.10 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.
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