SLM-5650 Satellite Modem
Revision 2
Introduction
MN/SLM5650.IOM
1–16
1.8.4 BER Performance with Symmetrical Adjacent Carriers
Operating in the presence of two adjacent symmetrical carriers (one lower in frequency and one
higher in frequency with same modulation, data rate, and coding), the modem performance is not
degraded more than as indicated in Table 1-10, Column three, and a and b. This performance is
measured with the adjacent carriers center frequencies offset X
R
s
Hz from the center frequency of
the carrier under test, where X is the spacing factor and R
s
is the modulation symbol rate in Hz of
the symmetrical carriers.
The BER of the test carrier is measured at the specified carrier Ratio of Energy per Symbol to
Noise Power Density in a 1 Hz Bandwidth (E
s
/N
0
) Carrier to Noise Ratio (C/N) without the
adjacent carriers. The adjacent carriers are applied at the specified center frequencies and E
s
/N
0
and
the BER of the test carrier is measured. The change in BER is equal to the change in E
b
/N
0
based
on the characterization curve of the test carrier and the amount of
A
djacent
C
hannel
I
nterference
(ACI) degradation. For modulation symbol rates below 38.4 ksps, this paragraph does not apply.
Table 1-10. Acceptable ACI Degradation with Spacing Factor of 1.2
Test
Carrier
E
s
/N
0
(dB)
Adjacent
Carriers
E
s
/N
0
(dB)
E
b
/N
0
Degradation
(dB)
Symmetric Case
E
b
/N
0
Degradation
(dB)
Asymmetric Case
5.5 18.5
< 0.36
< 0.41
6.0 19.0
< 0.38
< 0.43
8.0 21.0
< 0.48
< 0.56
8.4 21.4
< 0.51
< 0.60
10.0 23.0
< 0.64
< 0.77
12.0 25.0
< 0.88
< 1.10
12.7 25.7
< 0.99
< 1.21
a. For X (spacing factor) = 1.2, the symmetric degradation shall be IAW one of the values
in Table 1-17 Column three, and corresponding test carrier E
s
/N
0
in Column one. Select a
test carrier E
s
/N
0
that will yield timely results based on modulation and coding used in the
test configuration. The adjacent carriers E
s
/N
0
shall be set to corresponding value in
Column two.
b. For the case of X (spacing factor) = 1.4, the degradation is less than 0.2 dB.
