Figure P-2. Versafec Codes Vs. Constrained Capacity - Comtech EF Data CDM-570A Installation And Operation Manual

CDM-570A/570A Satellite Modem with Optional Packet Processor
Appendix P
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 P-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 P-1. The VersaFEC ModCod Set
Spectral
Code Rate efficiency,
bps/Hz
0.488 0.49
0.533 1.07
0.631 1.26
0.706 1.41
0.803 1.61
0.642 1.93
0.711 2.13
0.780 2.34
0.731 2.93
0.780 3.12
0.829 3.32
0.853 3.41

Figure P-2. VersaFEC Codes vs. Constrained Capacity

Block size, bits
2k
4.1k
4.1k
4.1k
4.1k
6.1k
6.1k
6.1k
8.2k
8.2k
8.2k
8.2k
P–7
MN-CDM570A
Revision 3
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