Ultra-Low-Latency (Ull) Codes; Table B-5. Ull Codes - Comtech EF Data CDM-570A Installation And Operation Manual

CDM-570A/570AL Satellite Modem with Optional Packet Processor
Appendix B
B.6.1.2

Ultra-Low-Latency (ULL) Codes

Four additional ultra-short block LDPC codes address the needs of users with applications
requiring even lower latency than the 'standard' VersaFEC code set. These codes, limited to
BPSK and QPSK only (see Table B-5), use significantly shorter code blocks than 'standard'
VersaFEC. As a result, the coding gain is slightly reduced. However, in terms of latency, the
performance is exceptional – far lower than any other FEC method ever offered, with the
exception of Viterbi.
Modulation
BPSK
QPSK
QPSK
QPSK

Table B-5. ULL Codes

Spectral
Code
efficiency, Eb/No, for
Rate
bps/Hz BER = 5 x 10
0.493 0.49
0.493 0.99
0.654 1.30
0.734 1.47
Typical Latency at
64 kbps, in
milliseconds
-8
3.3 dB 18
3.3 dB 19
3.8 dB 21
4.3 dB 23
B–9
MN-CDM570A
Revision 3
Min. Data Rate Max. Data Rate
(kbps) (Mbps)
2.4 1.479
4.8 2.959
6.3 3.923
7.0 4.405