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CDM-625 Advanced Satellite Modem
Adaptive Coding and Modulation (ACM)
Modulation
BPSK
QPSK
QPSK
QPSK
QPSK
8-QAM
8-QAM
8-QAM
16-QAM
16-QAM
16-QAM
16-QAM
The VersaFEC codes compared with the Shannon bound are shown below in Figure 17-2. It can be
seen that the performance of VersaFEC at or near the DVB-S2 performance with 16 kbit blocks.
Note that SNR is used in place of Eb/No, a convention for comparing ACM ModCods. SNR is
defined as Eb/No + 10log (Spectral Efficiency).
Table 17-1. The VersaFEC ModCod set
Spectral
Code
Block
efficiency,
Rate
size, bits
bps/Hz
0.488
0.49
2k
0.533
1.07
4.1k
0.631
1.26
4.1k
0.706
1.41
4.1k
0.803
1.61
4.1k
0.642
1.93
6.1k
0.711
2.13
6.1k
0.780
2.34
6.1k
0.731
2.93
8.2k
0.780
3.12
8.2k
0.829
3.32
8.2k
0.853
3.41
8.2k
Figure 17-2. VersaFEC Codes vs. Constrained Capacity
Typical
Latency at
Eb/No, for
64 kbps, in
BER = 5 x 10
milliseconds
-8
2.4 dB
26
2.2 dB
53
2.7 dB
59
3.4 dB
62
3.8 dB
66
4.6 dB
89
5.2 dB
93
5.6 dB
97
6.3 dB
125
7.0 dB
129
7.5 dB
131
8.0 dB
132
17–7
Revision 13
MN-CDM625
Min.
Max.
Data Rate,
Data Rate,
CCM mode
CCM mode
18 kbps
5.7 Mbps
20 kbps
10 Mbps
23 kbps
10 Mbps
26 kbps
10 Mbps
28 kbps
12 Mbps
35 kbps
12 Mbps
39 kbps
12 Mbps
43 kbps
12 Mbps
53 kbps
12 Mbps
57 kbps
14 Mbps
60 kbps
14 Mbps
62 kbps
16 Mbps
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