Cisco Model D-PCG1000 PowerKEY CAS Gateway Installation Guide
Theory of Operation
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7
Programs Entering a Switch/Router on Three GbE Interfaces
The following figure shows a switch/router with three GbE interfaces. Note that
each interface is bi-directional and some of the streams are flowing into the switch/
router and some out on the same interfaces (TSIDs). Also note that, in this example,
there is a mix of SPTSs and one MPTS (shown as TSID 5). All of the transport
streams are individually switchable to other interfaces, regardless of whether they
contain SPTSs or MPTSs. As long as all of the programs on the MPTS travel together,
no re-multiplexing is required. No PN or PID remapping is required, and no PSI
reconstruction is required.
Support for Table-Based QAMs
QAM modulators can generally be divided into two types based on how streams are
mapped from input to output of the modulator.
Session-based QAM modulators. In session-based QAM modulators (SB-
QAMs), such as our Gigabit QAM (GQAM) modulator, the mapping of input
streams to output carrier, MPEG PN, and PIDs is dynamically controlled and
assigned at session-setup time. SB-QAMs allow the ultimate flexibility and
mapping control for SPTSs and MPTSs over GbE. Session-based mapping more
easily accommodates both IP unicasts and multicasts.
Table-based QAM modulators. In table-based QAM modulators (TB-QAMs),
such as our eXtra Dense QAM Array (xDQA), the destination UDP port number
of an input stream is mapped to an output carrier, MPEG PN, and PIDs based on
a table or formula. This mapping is not dynamically altered in anticipation of
individual streams. TB-QAMs do not require communications with a controller
for input to output mapping to occur just prior to the arrival of each new stream.