Comtech EF Data CDD-562AL - Manual (Page 212)

CDD-562AL/564A/L Multi-Channel Demodulator Revision 0
Forward Error Correction MN-CDD562AL564AL
A–4
As a comparison, looking at LDPC Rate 2/3 8-QAM and VersaFEC Rate 0.642 8-QAM essentially identical
spectral efficiency and Eb/No performance. However, at 64 kbps, the latency has been reduced from 350
milliseconds to 89 milliseconds – a factor of 4 reduction.
The performance of the VersaFEC codes compared with the Shannon bound is shown in Figure A-1. This
puts the performance of VersaFEC at or near the DVB-S2 performance with 16 kbit blocks.
Figure A-1. VersaFEC Codes versus Shannon Capacity
Note that SNR is defined as Eb/No + 10
log
(Spectral Efficiency).