Comtech EF Data CDM-570A Installation And Operation Manual page 655

Remembering that, for the ACM case, the system latency is equal to the latency of the worst-case
ModCod, DVB-S2 shows a severe penalty. For 16k short blocks, this calculates to be 329
milliseconds (+ WAN Buffer delay) versus 34 milliseconds (+ WAN Buffer delay) for VersaFEC
ACM. For 64k block DVB-S2, the core latency is 4 times higher. Assuming a WAN Buffer of 20
milliseconds:
•
Latency for 64k block DVB-S2 ACM at 100 ksps = 1336 milliseconds
•
Latency for 16k block DVB-S2 ACM at 100 ksps = 349 milliseconds
•
Latency for VersaFEC ACM at 100 ksps = 54 milliseconds
•
For the example shown, the latency for a 16k block DVB-S2 ACM scheme is
approximately 7 times higher than VersaFEC ACM.
•
The latency for a 64k block DVB-S2 ACM scheme is approximately 25 times
higher than VersaFEC ACM.
Adaptive Coding and Modulation (ACM) Option
CDM-570A/570AL Satellite Modem with Optional Packet Processor
P–9
Revision 5
MN-CDM570A