Digital Signal Processing Reference
In-Depth Information
modulation, the more sensitive the transmission system. Fig. 16.5. shows
the variation of the bit error ratio with respect to the S/N ratio for QPSK,
16QAM, 64QAM and 256QAM.
BER for 4 / 16 / 64 / 256 QAM
BER for 4 / 16 / 64 / 256 QAM
0
0
1
1
10
10
BER
BER
1
1
1
1
10
10
2
2
1
1
10
10
ACTUAL C/N
ACTUAL C/N
3
3
1
1
10
10
END
END
NOISE MARGIN
NOISE MARGIN
4
4
1
1
10
10
5
5
1
1
10
10
6
6
1
1
10
10
7
7
1
1
10
10
8
8
1
1
10
10
9
9
1
1
10
10
256QAM
110
10
110
10
64QAM
11
11
1
1
10
10
16QAM
QPSK
12
12
1
1
10
10
4
4
6
6
8
8
10
10
12
12
14
14
16
16
18
18
20
20
22
22
24
24
26
26
28
28
30
30
32
32
34
34
36
36
38
38
40
40
C/N in dB
C/N in dB
S/N [dB]
S/N [dB]
Fig. 16.5.
Bit error ratio as a function of S/N in DVB-C [EFA]
Currently, the most widely used signals in coax networks are 64QAM-
modulated signals. These require a S/N ratio of more than 26 dB which
then corresponds to operation close to the “brick wall” (or “fall off the
cliff”).
Search WWH ::
Custom Search