CDM-840 Remote Router MN-CDM840
Appendix D Revision 3
D–11
• ACM maximizes throughput not only when Eb/No varies due to atmospheric conditions, but
will also mitigate the effects of other impairments, such as antenna pointing error, excessive
phase noise and certain types of interference. However, rapidly fluctuating impairments (i.e.,
~ less than 1 second) such as scintillation at low antenna look-angles at C-band will generally
not be improved by ACM.
D.6 Summary of Specifications
System type
Adaptive Coding and Modulation, using BPSK, QPSK, 8-QAM , 16-QAM and
VersaFEC short-block LDPC coding - total of 12 ModCods
10/100 BaseT 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
7:1 over range of adaptation
Switch point (decreasing SNR)
Corresponds to SNR (Es/No) that gives BER = 5 x 10
-8
Approximately 1 dB/second (higher if Target Eb/No margin > 1 dB)
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)
34 milliseconds max (not including WAN buffer, or satellite path)
Monitored parameters
•
• Local and Remote SNR
(-3.0 dB to +22.0 dB, 0.1 dB 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
(dB)
Min. Data Rate,
ACM mode
(kbps)
Max. Data Rate,
ACM mode
(Mbsp)
BPSK 0.488 0.49 2.4 16.00 2.19
QPSK 0.533 1.07 2.2 17.07 4.80
QPSK 0.631 1.26 2.7 20.19 5.67
QPSK 0.706 1.41 3.4 22.577 6.34
QPSK 0.803 1.61 3.8 25.69 7.22
8-QAM 0.642 1.93 4.6 30.83 8.67
8-QAM 0.711 2.13 5.2 34.14 9.60
8-QAM 0.780 2.34 5.6 37.44 10.53
16-QAM 0.731 2.93 6.5 46.80 13.26
16-QAM 0.829 3.32 7.7 53.04 14.91
16-QAM 0.853 3.41 8.1 54.60 15.35
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