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CDM-625A Advanced Satellite Modem
Introduction
1.4.8
VersaFEC Adaptive Coding and Modulation (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
Modulation
Code Rate
BPSK
0.488
QPSK
0.533
QPSK
0.631
QPSK
0.706
QPSK
0.803
8-QAM
0.642
8-QAM
0.711
8-QAM
0.780
16-QAM
0.731
16-QAM
0.780
16-QAM
0.829
16-QAM
0.853
Adaptive Coding and Modulation, using BPSK, QPSK, 8-QAM , 16-QAM and
VersaFEC short-block LDPC coding - 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 (ModCod0 through ModCod11)
Remote Demod Unlock Action: Maintain current ModCod
Target Eb/No margin (0 to 4.5 dB, 0.5 dB steps)
54 milliseconds max (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 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
Typical
Spectral efficiency,
Eb/No, for
bps/Hz
BER = 5 x 10
0.49
2.4 dB
1.07
2.2 dB
1.26
2.7 dB
1.41
3.4 dB
1.61
3.8 dB
1.93
4.6 dB
2.13
5.2 dB
2.34
5.6 dB
2.93
6.5 dB
3.12
7.1 dB
3.32
7.7 dB
3.41
8.1 dB
1–29
-8
Go to minimum ModCod
Min. Data
Rate,
ACM mode
-8
18.1 kbps
39.6 kbps
46.7 kbps
52.2 kbps
59.6 kbps
71.5 kbps
78.8 kbps
86.6 kbps
108.5 kbps
115.5 kbps
122.8 kbps
126.2 kbps
Revision 0
MN-CDM625A
Max. Data
Rate,
ACM mode
2.00 Mbps
4.38 Mbps
5.16 Mbps
5.78 Mbps
6.60 Mbps
7.91 Mbps
8.73 Mbps
9.59 Mbps
12.01 Mbps
12.79 Mbps
13.61 Mbps
14.00 Mbps
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