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CDM-625 Advanced Satellite Modem
Appendix B
Example: In the above diagram, the (Co+No)/No measured is 4.6 dB. If Rate 1/2 QPSK is used,
this corresponds to an E
table values is as follows:
E
/N
=10log
b
0
10
Where:
E
/N
•
b
0
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.
•
Note: Pay close attention to the sign of the middle term.
See Chapter 12. ESC++ for details of how the Eb/No performance degrades when
ESC++ is used, particularly at lower data rates, where the percentage overhead is
high.
/N
of approximately 2.6 dB. The exact relationship used to derive the
b
0
(10
-1)-10log
(Co+No/No)/10)
and (Co+No)/ No are expressed in dB;
(FEC Code Rate)-10log
10
B–2
Revision 13
MN-CDM625
(bits/symbol)
10
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