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A1.1.7.2 DVB-C2 Measurements
Power
Channel power, assuming that power spectral density is uniform over the
entire bandwidth of the channel.
C/N
(Carrier / Noise) where C is the received power of the modulated carrier
signal and N is the noise power received. To measure it correctly the channel
should be tuned at its centre frequency..
MER
Modulation Error ratio with indication of Link Margin(LM).The link margin
indicates the safety margin respect to the MER level , measured for the
degradation of the signal up to the QEF (Quasi Error Free) value. MER
represents the ratio between the average power of the DVB signal and the
average noise power of the signal constellation.
BER (CBER/LBER)
System error rate. In DVB-C2 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 interferences. On screen, under LBER measurement the number of
iterations LDPC is shown, that is, the number of times the LDPC decoder for
error correction has to pass through the signal and the ESR (Error Second
Ratio) that indicates the percentage of time with errors after the BCH. Error
correction is internal with BCH or external with LDPC. The internal error
correction provides basic minimum load while the outer error correction is a
correction with additional load. Also the PER measurement is displayed,
which is the number of erroneous packets, that is, packets received during
the measurement time and not correctable by the demodulator.
CBER (Channel Bit Error Rate)
BER of the signal after passing through the COFDM demodulator and before
applying the error correction or FEC (Forward Error Correction).
LBER (LDPC Bit Error Rate)
BER of the signal after applying the correction errors LDPC (Low-density
parity-check).
12 August 2012