Digital Video Broadcasting (DVB); User guidelines for Digital ...

Clear sky margin (dB)
18
16
14
12
10
8
6
4
2
0
QPSK
1/2
Figure 6.- Clear sky margin for fixed contribution links considering different
receiving earth stations (8.1 m, 4.5 m and 2.4 m) located at beam
centre.Transponder operated in "Nominal Gain-3 dB".
QPSK
2/3
QPSK
3/4
QPSK
5/6
QPSK
7/8
8PSK
2/3
Modulation scheme
8PSK
5/6
20
8PSK
8/9
2.4.4. Interfacing with terrestrial telecommunications networks
There is the possibility within the specified system to allow interworking between satellite and
terrestrial digital networks.
The connection of the system with the terrestrial telecommunications networks is illustrated in Figure
5. Table 4 shows the symbol rates and their corresponding bandwidth that would be suitable for
connection to a PDH terrestrial networks at 34368 Kb/s, where the transmission capacity of 29140
Kb/s after Reed Solomon coding.
Table 4.- Examples of Symbol rates using QPSK, 8PSK and 16QAM for 29.140 Mb/s bit rate after RS.
QPSK 8PSK (Optional) 16QAM
(Optional)
1/2 2/3 3/4 5/6 7/8 2/3 5/6 8/9 3/4 7/8
Rs
(Mbaud) 29.14 21.86 19.93 17.48 16.65 10.93 8.74 8.20 4.86 4.16
BW=Rsx1.35
(Rsx1.25
Optional)
(MHz)
39.34 29.50 26.23
23.60 22.48 14.75
(13.66)
16QAM
3/4
16QAM
7/8
11.80
(10.93)
11.06
(10.25)
6.56
(6.08)
8,1 m
4,5 m
2,4 m
5.62
(5.20)
In order to provide an example of the system for connection to a PDH terrestrial networks, it is
considered a 72 MHz transponder splitted in 4 equals 18 MHz slots. The following configuration is
suitable for this application:
• Ru + Rs = 29.140 Mb/s
• 8PSK FEC 2/3
• Rs = 10.928 Mbaud
• Rs x 1.35 = 14.8 MHz (compatible with 18 MHz bandwidth slot)
• Fixed contribution link between 8.1 m earth stations, located at beam center for 99.9% availability
(zone K).
Figure 5.- Example of Connection of the System with Terrestrial PDH Network following ETS
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