Comtech EF Data CDM-625 - Manual (Page 62)

CDM-625 Advanced Satellite Modem Revision 15
Introduction MN-CDM625
1–26
VersaFEC (ANY MODE) Lower Limit (kbps) Upper Limit (kbps)
VersaFEC BPSK Rate 0.488 18.0 5700.0
VersaFEC QPSK Rate 0.533 20.0 10000.0
VersaFEC QPSK Rate 0.631 23.0 10000.0
VersaFEC QPSK Rate 0.706 26.0 10000.0
VersaFEC QPSK Rate 0.803 28.0 12000.0
VersaFEC 8-QAM Rate 0.576 (ECCM) 32.0 11000.0
VersaFEC 8-QAM Rate 0.642 35.0 12000.0
VersaFEC 8-QAM Rate 0.711 39.0 12000.0
VersaFEC 8-QAM Rate 0.780 43.0 12000.0
VersaFEC 16-QAM Rate 0.644 (ECCM) 47.0 11000.0
VersaFEC 16-QAM Rate 0.731 53.0 12000.0
VersaFEC 16-QAM Rate 0.780 57.0 14000.0
VersaFEC 16-QAM Rate 0.829 60.0 14000.0
VersaFEC 16-QAM Rate 0.853 62.0 16000.0
ULL BPSK Rate 0.493 18.0 5700.0
ULL QPSK Rate 0.493 18.0 6000.0
ULL QPSK Rate 0.654 24.0 9000.0
ULL QPSK Rate 0.734 27.0 9000.0
VersaFEC Adaptive Coding and Modulation (ACM): See Specifications that follow (Sect.1.4.8)
1.4.8 VersaFEC Adaptive Coding and Modulation (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 Teporting
Automatically reported from remote modem – built in function at the physical
layer – requires no additional overhead
Maximum Span of Data Rate 7:1 over range of adaptation
Switch Point (Decreasing
SNR)
Corresponds to SNR (Eb/No) that gives BER=5 x 10 -8
Switch Point Hysteresis 0.3 dB
Maximum Fading Rate Approximately 1 dB/second (higher if Target Eb/No margin >1 dB)
Maximum ModCod Update
Rate
One update every two seconds (no restriction on distance between ModCods)
Configurable Parameters
MIN and MAX ModCod (ModCod0 through ModCod11)
Remote Demod Unlock Action: Maintain current ModCod, Go to MIN ModCod
Target Eb/No margin (0-4.5 dB, 0.5 dB steps)
System Latency
54 ms max. (for a system operating at 100 ksps, and assuming a WAN
buffer of 20 ms, not including satellite path)
Monitored Parameters
Tx and Rx ModCods
Local and Remote SNR
(–3.0 to +22.0dB, 0.1dB resolution, ±0.5 dB accuracy)
Configuration and monitor menus displaying data rate, modulation and code rate update
dynamically with ModCod