Versafec Adaptive Coding And Modulation (Acm); Versafec Acm - Comtech EF Data CDM-425 Installation And Operation Manual

1.4.7

VersaFEC Adaptive Coding and Modulation (ACM)

1.4.7.1

VersaFEC ACM

System type
Symbol Rate Range
Interface
Remote SNR reporting
Max span of data rate
Switch point
(decreasing SNR)
Switch point hysteresis
Max fading rate
Max ModCod update rate
Configurable parameters
System latency
Monitored parameters
Introduction
Adaptive Coding and Modulation, using BPSK, QPSK, 8-QAM , 16-QAM and
VersaFEC short-block LDPC coding – a total of 12 ModCods
37 ksps to 4100 ksps
10/100 Base T Ethernet, with auto-negotiated Congestion Control
Automatically reported from remote modem – built in function at the physical
layer – requires no additional overhead
7:1 over range of adaptation
Corresponds to SNR (Eb/No) that gives BER = 5 x 10
0.3 dB
Approximately 1 dB/second (higher if Target Eb/No margin > 1 dB)
1 update every 2 seconds
Minimum and Maximum ModCod (ModCods 00-11)
Remote Demod Unlock Action: Maintain current ModCod
Target Eb/No margin (0 to 4.5 dB, 0.5 dB steps)
54 milliseconds maximum (for a system operating at 100 ksps, and assuming a WAN
buffer of 20 milliseconds, not including satellite path)
Tx and Rx ModCods
Local and Remote signal to noise ratio (SNR)
(-3.0 dB to +22.0dB, 0.1dB resolution, +/- 0.5 dB accuracy)
Config and monitor menus displaying data rate, modulation and code rate update
dynamically with ModCod
1–29
CDM-425 Advanced Satellite Modem
-8
Go to minimum ModCod
Revision 0
MN-CDM-425