Comtech EF Data SDM-9000 - Manual (Page 196)

Options SDM-9000 Satellite Modem
A–10 Rev. 4
A.2 Direct Broadcast Satellite
This section describes the optional Direct Broadcast Satellite (DBS) operating mode for
the SDM-9000.
As implemented on the SDM-9000, the DBS mode supports data rates up to
44.736 Mbit/s using a single FEC (Forward Error Correction) channel. Single channel
implementation differs significantly from the INTELSAT specifications (for carriers
greater than 10 Mbit/s) for commutating the data across three channels.
In addition, DBS mode employs the following features:
•
Special framing
•
Scrambling
•
Reed-Solomon coding
•
Code rate puncturing
DBS operation with the SDM-9000 is based on the European Broadcasting Union (EBU)
DVB specifications of DVB SB 5 (94) 5 and ETS 300 421. Both of these specifications
describe channel coding, modulation, etc., for transmitting MPEG-2 (ISO/IEC 13818)
coded television over a satellite link.
Figure A-6 shows the conceptual block diagrams for the transmit and receive processes
of the SDM-9000 when configured for DBS operation.
Note: The IF physical interfaces and QPSK modulator are functionally equivalent to
those used during INTELSAT operation, and will not be described here.
The blocks shown in Figure A-6 have special functionality when operating in DBS
mode. Each block is described in the following sections.