Comtech EF Data CDM-750 - Manual (Page 249)

CDM-750 Advanced High-Speed Trunking Modem Revision 2
Appendix C MN-CDM750
C–13
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0
Sp
e
ct
ra
l E
ff
ici
e
n
cy
(B
p
s/
H
z)
Es/No (dB)
32APSK
16APSK
8PSK
QPSK
Pruned ModCods Appear On Baseline
Figure C‐6 presents a practical set of ModCods based on ModCod selection. The pruned or
inactive ModCods are shown along the baseline of the plot. The transition to the next higher
ModCod is the Es/No (spec) + Es/No Target Margin (user selected) + hysteresis (0.5 dB) +
modulation impairment (user selected), while a step down is the Es/No (spec) + Es/No Target
Margin + modulation impairment. In the example, the Target Es/No Margin and Modulation
Impairment are zero.
Figure C-6. Spectral Efficiency vs. Modem Es/No @ QEF (Pruned ModCods)