Comtech EF Data CDM-425, Installation And Operation Manual

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CDM-425 Advanced Satellite Modem
Revision 0
Appendix G G–2 MN-CDM-425
Figure G-1. (Co+No)/No Measured Example
G.1.1 (Co+No)/No Example
In Figure G-1, the (Co+No)/No measured is 4.6 dB. If Rate 1/2 QPSK is used, this corresponds to
an E
b
/N
0
of approximately 2.6 dB. The exact relationship used to derive the table values is as
follows:
E
b
/N
0
=10log
10
(10
(Co+No/No)/10)
-1)-10log
10
(FEC Code Rate)-10log
10
(bits/symbol)
Where:
•
E
b
/N
0
and
(Co+No)/ No
are expressed in dB;
•
bits/symbol
= 1 for BPSK;
•
bits/symbol
= 2 for QPSK;
•
bits/symbol
= 3 for 8-PSK/8-QAM;
•
bits/symbol
= 4 for 16-QAM;
•
FEC Code Rate
for ‘uncoded’ = 1.
Pay close attention to the sign of the middle term.
See Figure G-2 for the Eb/No Table.