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Series 2000/3000 IDU User’s Manual
Revision P4
• The return link carries communication from SITs to the gateway and uses a multi-fre-
quency time-division multiple access (MF-TDMA) scheme carrying ATM cells.
Return link communication is normally in the Ku or Ka band.
In the figure below, dotted lines indicate forward link communication and solid lines indi-
cate return link communication.
Figure 1.1 Digital Video Broadcast-Return Channel System (DVB-RCS)
1.3.2 Satellite Interactive Terminals (SITs)
SITs are made up of two components, as shown in the figure below.
• The outdoor unit (ODU) consists of an antenna subsystem and an RF transceiver
assembly. The antenna is mainly made up of a reflector dish, a LNB that provides the
forward link signal, a transmitter (or BUC) that generates the return link signal, and
feedhorn/OMT.
• The ODU is connected via two inter-facility link (IFL) cables to the IDU. The IDU is
responsible for the network access and is the ethernet interface with the LAN or host
computers.
ISP
ISDN
B-ISDN/ATM
Terrestrial network
SIT
(e.g., SMATV, LAN)
Hub
SIT
SIT