Dvb And Dvb-S2 Modulators - Hughes HX System System Overview

DVB and DVB-S2
modulators
• Timing unit (TU)
• Conditional access controller
Satellite gateways can receive encapsulated traffic using multicast
addressing.
The maximum length of the packets is configurable for each IP
gateway. A maximum expected frame length is also configured
into each satellite gateway and must be at least as large as the
largest corresponding value configured in the IP gateways feeding
that satellite gateway. The UDP frames are all destined to a single
IP multicast address. The frames contain sequence numbers and
other header information and one or more user traffic frames.
Multicast traffic is received over the satellite gateway multicast
address. This multicast address is unique across transponders.
The conditional access (CA) key traffic is received over the CAC
multicast address. This address is common to all satellite
gateways configured in the NOC. The common CAC address and
the unique satellite gateway address allow a single LAN
configuration to support multiple transponders. All traffic to the
satellite gateway is sent via multicast. The satellite gateway can
receive traffic on multiple (a maximum of 8) multicast addresses.
Each satellite gateway connects to a DVB or DVB-S2 modulator.
The modulators are paired to satellite gateways and are designed
to switch together as a chain in the event of a failure. The DVB
modulators provide a 70 MHz IF output that is fed into an
outroute redundancy module and then onto the uplink system of
the RF terminal.
Two standards are supported, DVB-S and DVB-S2. Modulators
can be configured to support DVB-S only or both standards.
• DVB-S supports Reed-Solomon coding and QPSK
modulation
• DVB-S2 supports LDPC coding in both QPSK and 8PSK
modulation.
The modulator supports the following symbol rates:
• In DVB-S mode, the DVB modulator supports the following
symbol rates: 1.25, 2.5, 5, and 10 - 45 Msps, using FEC rates
up to 7/8.
• In DVB-S2 mode, the DVB modulator supports symbol rates
of 1–45 Msps in 1 Msps increments. The supported FEC rates
depend upon the frame length (short codeblock or normal
codeblock) and type of modulation:
– Short, QPSK modulation: 1/2, 3/5, 2/3, 3/4, 4/5, 5/6, 8/9
– Short, 8PSK modulation: 3/5, 2/3, 3/4, 5/6, 8/9
(
CAC) server
Chapter 2 • Subsystems
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