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CDM-Qx Satellite Modem
CnCPerformance Characterization
The following CDM-Qx configurations were tested for Eb/No degradation as a function
of CnC ratio:
Modulation
The Eb/No degradation is the difference between the reference Eb/No with no interfering
carrier present and the Eb/No reported by the modem at a given CnC ratio.
Figure D-7 plots the impact of CnC ratio on QPSK and 8-PSK constellations, while
Figure D-8 shows 16-QAM. In general, the higher the operating C/N of a carrier, the
more sensitive it is to degradation. QPSK is the least sensitive to CnC ratio followed by
8-PSK and 16-QAM.
Eb/No Degradation vs CnC Ratio (QPSK)
0.0
-0.1
-0.2
-0.3
QPSK 17/18 Turbo
QPSK 3/4 Turbo
-0.4
QPSK 21/44 Turbo
QPSK 7/8 Turbo
-0.5
-10
-5
Forward Error
Correction
21/44 Turbo
3/4 Turbo
QPSK
7/8 Turbo
17/18 Turbo
2/3 TCM
3/4 Turbo
8-PSK
7/8 Turbo
17/18 Turbo
3/4 Turbo
16-QAM
7/8 Turbo
0
5
CnC Ratio (dB)
Figure D-7. CnC Ratio For QPSK and 8-PSK
Reference Eb/No
-6
At BER ≈ 10
2.6 dB
3.7 dB
4.3 dB
6.5 dB
5.3 dB
6.1 dB
7.1 dB
9.0 dB
7.2 dB
8.1 dB
Eb/No Degradation vs CnC Ratio (8-PSK)
0.0
-0.2
-0.4
-0.6
8-PSK 2/3 TCM
-0.8
8-PSK 7/8 Turbo
8-PSK 3/4 Turbo
-1.0
8-PSK 17/18 Turbo
-1.2
10
-10
D–7
Revision 6
MN/CDMQx.IOM
C/N
2.4 dB
5.5 dB
6.7 dB
9.3 dB
7.9 dB
9.6 dB
11.3 dB
13.5 dB
12.0 dB
13.5 dB
-5
0
CnC Ratio (dB)
5
10
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