CDM-Qx Satellite Modem

Revision 5

CnCPerformance Characterization

MN/CDMQx.IOM

The following CDM-Qx configurations were tested for Eb/No degradation as a function of CnC ratio:

Modulation

Forward Error

Reference Eb/No

C/N

 

Correction

At BER ≈ 10-6

 

QPSK

21/44 Turbo

2.6 dB

2.4 dB

QPSK

3/4 Turbo

3.7 dB

5.5 dB

QPSK

7/8 Turbo

4.3 dB

6.7 dB

QPSK

17/18 Turbo

6.5 dB

9.3 dB

8-PSK

2/3 TCM

5.3 dB

7.9 dB

8-PSK

3/4 Turbo

6.1 dB

9.6 dB

8-PSK

7/8 Turbo

7.1 dB

11.3 dB

8-PSK

17/18 Turbo

9.0 dB

13.5 dB

16-QAM

3/4 Turbo

7.2 dB

12.0 dB

16-QAM

7/8 Turbo

8.1 dB

13.5 dB

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- plots the impact of CnC ratio on QPSK and 8-PSK constellations, and Figure D-8shows 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)

 

 

 

Eb/No Degradation vs CnC Ratio (8-PSK)

 

 

0.0

 

 

 

 

 

0.0

 

 

 

 

Degradation(dB)

-0.1

 

 

 

 

 

-0.2

 

 

 

 

 

 

 

 

Degradation(dB)

 

 

 

 

 

-0.3

 

 

 

 

-0.4

 

 

 

 

 

-0.2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

-0.6

 

 

 

 

Eb/No

 

QPSK 17/18 Turbo

 

 

 

Eb/No

-0.8

8-PSK 2/3 TCM

 

 

 

 

QPSK 3/4 Turbo

 

 

 

8-PSK 7/8 Turbo

 

 

 

 

 

 

 

 

 

 

 

 

 

-0.4

 

 

 

 

 

 

 

 

 

QPSK 21/44 Turbo

 

 

 

 

-1.0

8-PSK 3/4 Turbo

 

 

 

 

 

QPSK 7/8 Turbo

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

8-PSK 17/18 Turbo

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

-0.5

 

 

 

 

 

-1.2

 

 

 

 

 

-10

-5

0

5

10

 

-10

-5

0

5

10

 

 

 

CnC Ratio (dB)

 

 

 

 

 

CnC Ratio (dB)

 

 

Figure D-7. CnC Ratio For QPSK and 8-PSK

D–7

Page 249
Image 249
Mocomtech CDM-QX operation manual Figure D-7. CnC Ratio For Qpsk and 8-PSK