Comtech EF Data CDM-625A - Manual (Page 75)

CDM-625A Advanced Satellite Modem MN-CDM625A
Introduction Revision 3
1–31
1.4.8.2 VersaFEC-2 ACM
System type
Adaptive Coding and Modulation, using BPSK, QPSK, 8-ARY, 16-ARY, 32-ARY and
VersaFEC-2 Short-block and Long Block LDPC coding - total of 74 ModCods
Symbol Rate Range 37 ksps to 12.5 Msps (Long)
Interface 10/100 Base T Ethernet, with auto-negotiated Congestion Control
Remote SNR reporting
Automatically reported from remote modem – built in function at the physical
layer – requires no additional overhead
Max span of data rate 9:1 over range of adaptation
Switch point (decreasing SNR) Corresponds to SNR (Es/No) that gives BER = 1 x 10 -8 (margin set to 0 dB)
Switch point hysteresis 0.3 dB
Max fading rate Approximately 1 dB/second (higher if Target Eb/No margin > 1 dB)
Max ModCod update rate 1 update every 1.7 seconds
Configurable parameters
• Maximum ModCod (ModCod00 through ModCod37, Long Block)
• Maximum ModCod (ModCod00 through ModCod35, Short Block)
• Remote Demod Unlock Action: Go to minimum ModCod
• Target SNR margin (0 to 4.5 dB, 0.5 dB steps)
System latency @ 100 ksps
Long Block - 205 milliseconds max (not including WAN buffer, or satellite path)
Short Block – 40.4 milliseconds max (not including WAN buffer, or satellite path)
Monitored parameters
• Tx and Rx ModCods
• Local and Remote 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
List of ModCods See Tables 1-3 and 1-4