Comtech EF Data CDM-625A - Page 702

CDM-625A Advanced Satellite Modem MN-CDM625A
Appendix M Revision 4
M–22
M.12 Summary of Specifications
M.12.1 VersaFEC ACM
System type
Adaptive Coding and Modulation, using BPSK, QPSK, 8-QAM , 16-QAM and
VersaFEC short-block LDPC coding - total of 12 ModCods
Symbol Rate Range 37 ksps to 4100 ksps
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 7:1 over range of adaptation
Switch point (decreasing SNR) Corresponds to SNR (Es/No) that gives BER = 5 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 2 seconds
Configurable parameters
•
Minimum and Maximum ModCod (ModCod0 through ModCod11)
• Remote Demod Unlock Action: Maintain current ModCod
Go to minimum ModCod
•
Target SNR margin (0 to 4.5 dB, 0.5 dB steps)
System latency 34 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
Modulation Code Rate
Spectral
Efficiency, bps/Hz
Typical
Eb/No, for
BER = 5 x 10
-8
Min. Data Rate,
ACM mode
Max. Data Rate,
ACM mode
BPSK 0.488 0.49 2.4 dB 18.1 kbps 2.00 Mbps
QPSK 0.533 1.07 2.2 dB 39.6 kbps 4.38 Mbps
QPSK 0.631 1.26 2.7 dB 46.7 kbps 5.16 Mbps
QPSK 0.706 1.41 3.4 dB 52.2 kbps 5.78 Mbps
QPSK 0.803 1.61 3.8 dB 59.6 kbps 6.60 Mbps
8-QAM 0.642 1.93 4.6 dB 71.5 kbps 7.91 Mbps
8-QAM 0.711 2.13 5.2 dB 78.8 kbps 8.73 Mbps
8-QAM 0.780 2.34 5.6 dB 86.6 kbps 9.59 Mbps
16-QAM 0.731 2.93 6.5 dB 108.5 kbps 12.01 Mbps
16-QAM 0.780 3.12 7.1 dB 115.5 kbps 12.79 Mbps
16-QAM 0.829 3.32 7.7 dB 122.8 kbps 13.61 Mbps
16-QAM 0.853 3.41 8.1 dB 126.2 kbps 14.00 Mbps