Promax US TV EXPLORER 2 User Manual página 68

In a digital reception system for satellite signals (DVB-S2), after the QPSK
decoder other two different correction methods are applied (see following Figure). In
this case, as the previous one, each time we apply an error corrector to a digital signal,
the error rate changes, therefore if we measure in a digital satellite television system, for
example, the error rate at the output of the QPSK/8PSK demodulator, at the output of
the Low Density Parity Check (LDPC) decoder, and at the output of the BCH decoder,
we obtain nothing more than different error rates. This is the reason because the BER
measurement is provided after LDPC (LBER). Also stating the Packet Error Ratio
(PER) as packets non-correctable received by the demodulator during the
measurement elapsed time.
Figure 38.- Digital reception system via satellite. (DVB-S2)
PER: 0
FREC:
DL-Ku:
CAN:
MPEG-2 TS
Figure 39.- DVB-S2 (QPSK/8PSK) signals LBER measurement screen.
The DSS (Direct Satellite System) is a video and audio distribution system to
broadcast digital TV over Ku-Band and C-Band. The DSS utilizes QPSK modulation,
with 127-byte packets and the Viterbi and Reed-Solomon algorithms for error detection
and correction, with variable FEC rate to squeeze the maximum available bandwidth out
of each satellite transponder. The DSS systems typically utilize a video encoding
scheme very similar to, but not compatible with, the final MPEG-2 standard.
The DSS is a type of DBS (Direct Broadcast Satellite) system, which are also
referred to as mini-dish systems, because they use smaller (18") dishes than the
previous generation of C Band systems.
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USER'S MANUAL. US TV EXPLORER II
ELAPSED TIME: 00:00:05
2121.97 MHz C/N: 16.1
-1657 kHz POTEN.: 69.8
12722.0 MHz MER: 12.6
119 CBER: 1.1E-1
» L BER: 2.7E-7
dB
dBµV
dB
10/2007