Product specifications

CDM-710 Broadcast Satellite Modem Revision 11
Forward Error Correction Options MN/CDM710.IOM
7–3
Another useful parameter is the occupied bandwidth is the bandwidth between -10 dB
points of the power spectral density, which are approximately:
Occupied Bandwidth = 1.19
x Symbol Rate, for 35% Rolloff
= 1.15
x Symbol Rate, for 25% Rolloff
= 1.12 x Symbol Rate, for 20% Rolloff
Table 7-1 provides the Eb/No, spectral efficiency a
nd occupied bandwidth for the CDM-710.
Table 7-2 and Table 7-3 outline these pa
rameters per the modem’s DVB schemes.
Figure 7-1 through Figure 7-7 illustrate the error performance characteristics. To convert
Es/No to Eb/No:
Eb/No = Es/No - 10xLog(Spectral Efficiency)
Table 7-1. Eb/No, Spectral Efficiency and Occupied Bandwidth*
Mode Type FEC Code
Inner
Code
Rate
Eb/No
at QEF
Spectral
Efficiency
(bps/Hz)
Normalized
S
y
mbol Rate
(
=
Bit Rate x)
Occupied *
Bandwidth for
10 Mbps (35%
Rolloff)
DVB-S QPSK Conv+RS 1/2 4.5 0.921569 1.085 12.913
QPSK Conv+RS 2/3 5.0 1.228758 0.814 9.685
QPSK Conv+RS 3/4 5.5 1.382353 0.723 8.609
QPSK Conv+RS 5/6 6.0 1.535948 0.651 7.748
QPSK Conv+RS 7/8 6.4 1.612745 0.620 7.379
DVB-DSNG 8-PSK Conv+RS 2/3 6.9 1.843137 0.543 6.456
8-PSK Conv+RS 5/6 8.9 2.303922 0.434 5.165
8-PSK Conv+RS 8/9 9.4 2.457516 0.407 4.842
16-QAM Conv+RS 3/4 9.0 2.764706 0.362 4.304
16-QAM Conv+RS 7/8 10.7 3.225490 0.310 3.689
* Taken at the -10 dB points on the plot of power spectral density, the occupied bandwidth is 1.19 x
Symbol Rate for 35%, and 1.15 x Symbol Rate for 25%.