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A1.1.3.2 DVB-T2 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.
PLP id
It is the PLP identifier. In the case of PLP Single mode identifies the input
stream (0-255).In the case of PLP Multiple mode clients can choose the PLP
ID to view.
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)
It is the bit error rate. There are two measurements related to BER:
CBER (Channel Bit Error Rate):
BER of the signal after the COFDM demodulator and before applying the
error correction or FEC (Forward Error Correction).
LBER (LDPC Bit Error Rate):
BER after been applied the LDPC (Low-density parity-check) error
correction.
In a digital signal reception (DVB-T2), after the COFDM decoder two methods
of error correction are applied. DVB-T2 uses two codes to correct errors that
are the LDPC (Low Density Parity Check) combined with the BCH (Bose-
Chaudhuri - Hocquengham) to protect against high levels of signal noise and
interferences. Next to the measurement LBER is shown the number of
iterations LDPC, that is, the number of times the LDPC error correction
decoder has to pass through the signal and the ESR (Error Second Ratio)
after 20 seconds of the BCH decoder. This measure indicates the percentage
of time with errors after the BCH. Error correction is internal with BCH and
external with LDPC. The internal gives basic error correction with minimum
load while the external gives error correction with a correction additional
charge.
4 August 2012