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Chapter 1 Introducing the MQAM
Input/Output Diagram
The following diagram illustrates the stages of the input/output process for the
MQAM.
Note: The stage numbers correspond with the following table.
Input/Output Stage/Description Table
The following table describes the stages of the I/O process of the MQAM. The
numbers correspond to the above I/O diagram.
Stage
Description
1
MPEG TS packets are received. The MQAM ASI input ports receive data from
different physical layer sources and extract the MPEG TS packets.
2
Packets are routed. The digital I/O board timestamps the packets and filters
them according to their PID values.
3
Conditional Access is added. The digital I/O board implements PowerKEY
Conditional Access.
Note: The digital I/O board also inserts ECMs and Entitlement Management
Messages (EMMs) into the MPEG TS packet stream.
4
Packets are transferred to the QAM RF Board. The digital I/O board provides
a constant stream of MPEG TS packets to each modulator board. If no packets
are available for the modulator boards, the digital I/O board generates an
MPEG stuff packet.
5
Data frame is assembled. The QAM RF Board assembles the MPEG packets
into a transmission data frame. Forward Error Correction (FEC) parity bytes
are added to the data, and interleaving and scrambling are performed on the
data for the selected ITU-T specification.
6
Data frame is modulated. The modulator board modulates the data frame.
7
Signal is output through four, independent QAM Modulator output
assemblies with a QAM signal frequency between 91 and 867 MHz.
6
78-717866-01 Rev D
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Troubleshooting
