Versafec Acm Latency; Table H-2. Example Case - Versafec Implementation Of Acm (100 Ksymbols/Sec; Figure H-1. Versafec Codes Vs. Constrained Capacity - Comtech EF Data CDD-880 Installation And Operation Manual

CDD-880 Multi Receiver Router
Appendix H

VersaFEC ACM Latency

H.3.1
Examining the data in Table H-2, latency for each MODCOD is shown for the example of
VersaFEC ACM at a fixed 100 ksymbols/second rate. Of particular note is that even though the
MODCODs span a 7:1 variation in throughput, the latency is only varying between 25 and 34
milliseconds. In the example shown the worst-case latency for this ACM scheme is 34
milliseconds.
Table H-2. Example Case – VersaFEC Implementation of ACM (100 ksymbols/sec)
Modulation
(MODCOD No.)
BPSK (00)
QPSK (01)
QPSK (02)
QPSK (03)
QPSK (04)
8-QAM (05)
8-QAM (06)
8-QAM (07)
16-QAM (08)
16-QAM (09)
16-QAM (10)
16-QAM (11)

Figure H-1. VersaFEC Codes vs. Constrained Capacity

Code Rate
0.488
0.533
0.631
0.706
0.803
0.642
0.711
0.780
0.731
0.780
0.829
0.853
OVERALL SYSTEM LATENCY = Worst-case MODCOD (MODCOD 00)
Latency = 34 milliseconds, NOT INCLUDING WAN BUFFER OR SATELLITE PATH
Spectral Efficiency Bit Rate (Throughput)
(bps/Hz)
0.49
1.07
1.26
1.41
1.61
1.93
2.13
2.34
2.93
3.12
3.32
3.41
H–4
MN-CDD880
Minimum Latency
(in kbps) (in milliseconds)
49 34
107 32
126 30
141 28
161 26
193 30
213 28
234 27
293 27
312 26
332 25
341 25
Revision 2