() . , / S/N ( 52023-2003 43 dB), , QAM (Quadrature Amplitude Modulation ). S/N BER (Bit Error Rate ) . , .
, , , (CSO ), , S/D ( / ) . QAM , , .
, .. , 4-6 , 25-35 5-7 , .
() . , MPEG-2 , . , . DVB DVB, .. . DVB-C DVB-S.
DVB-C
DVB-C ( DVB-C) DVB-S, QPSK, M - QAM 16 256 (.. 16 QAM 256 QAM).
. 9.1 , , - .
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|
. 9.1. DVB-C
MPEG-2 , : , , .. , , RS- DVB-S DVB-. ( , ) , QAM.
, , QAM . I Q. I Q , QAM , . Set - Top - Box (STB).
. -.
, QAM, .. .
. m = log2(M), M - QAM (.. 2 m×QAM).
:
8k = n×m,
: k 8 ;
n m .
M - QAM , .9.2.
9.2
m | n | k | 8k = nm | |
16QAM | ||||
32QAM | ||||
64QAM | ||||
128QAM | ||||
256QAM |
1 16QAM 256 QAM 256 QAM .
.9.3 8 .
38,1 /, 33 F = 27,5 /, CR = 3/4.