Promax HD RANGER 2 User Manual page 159

MER
Modulation Error ratio. MER represents the ratio between the average
power of the DVB signal and the average noise power of the signal
constellation.
Next to the MER appears the Link Margin (LM) measurement. The LM is
equivalent to the noise margin (NM) and indicates the distance to the QEF
(usually defined as a one lost packet per hour).The LM is measured in dB
and its value corresponds to the safety margin that separates from the
QEF. The greater is the LM better the quality signal. LM of negative values
implies no reception or that video errors are starting to appear in the
video or audio so clear. LM of 0 (zero) value will display a service and
occasionally some artefact.
BER (CBER/LBER)
It is the bit error rate. There are two measurements related to BER:
CBER (Channel Bit Error Rate):
BER of the signal after the QPSK/8PSK demodulator and before
applying the error correction or FEC (Forward Error Correction).
LBER (LDPC Bit Error Rate):
BER after applying LDPC error correction (Low-density parity-check).
This standard makes use of two codes to correct errors that are the LDPC
(Low Density Parity Check) codes combined with BCH (Bose-Chaudhuri -
Hocquengham) to protect against high levels of signal noise and
interference. Each time you apply an error correction to the digital signal,
the error rate changes, so if we measure the error rate at the output of
the QPSK/8PSK demodulator or after LDPC (Low Density Parity Check)
decoder or at the BCH decoder output, error rates obtained are different.
Next to the LBER measure appears ESR (Error Second Ratio).This
measures indicates the percentage of time with errors after BCH. The
error correction is internal with BCH or external with LDPC. The internal
error correction provides basic minimum load while the outer error
correction is an additional correction with load. It also measures the PER,
which is the number of erroneous packets, that is packets received during
the measurement time not correctable by the demodulator.
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June 2014