Comtech EF Data CDM-600/600L - Manual (Page 188)

CDM-600/600L Open Network Satellite Modem Revision 3
Appendix B MN/CDM600L.IOM
B–2
Example: In the diagram that follows, the (Co+No)/No measured is 4.6 dB. If Rate 1/2 QPSK is
being used, this would correspond to an Eb/No of approximately 2.6 dB.
The exact relationship used to derive the table values is as follows:
E
b
/N
0
= 10 log
10
(10
(Co+No/No )/10)
-1) - 10 log
10
(FEC Code Rate) - 10 log
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
• Code Rate for ‘uncoded’ = 1
• Pay close attention to the sign of the middle term