WavePhore Networks IDR V1000, Руководство пользователя

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Functional Overview
5– 4 MS-4900, Rev. A
The Receiver:
Input and
Output Input to the IDR V1000 comes from the satellite dish. The downlinked data stream
is amplified and shifted to a lower frequency by the
LNB on the satellite dish and
passed through the coaxial cable to the IDR V1000. The receiver demodulates the
data, converting the analog signal to digital data, and tries to correct reception errors
before moving the digitized data stream to the
time-division demultiplexer , or TDD .
The TDD decodes the aggregate data stream into partitions that correspond to the
TDM input channels. Some of the data stream can pass directly from the TDD to an
output port. Other streams are routed through the CPU for additional processing.
For example, the data originally statistically multiplexed at the NCC—must be
processed through a
statistical demultiplexer in the CPU.
The statistical demultiplexer , or stat demux reads the data in the channel, applies a
second level of error correction, and reads packets in the resulting data stream. It
strips the packets of control information, and processes the message accordingly,
applying any necessary decrypting, decompressing, or routing to a specific output
device.
The IDR V1000 processor also interfaces with the front panel. The processor
updates the LCD screens and processes the user input from the front panel buttons
to change tuner settings, port configurations, logging, etc. Network operators can
update receiver settings, individually or as groups, by downloading new
configuration parameters to the receiver or receivers.
Modes of
Moving
Data
The data being moved throughout the network originate in multiple locations, each
of which might be subject to different economic, environmental, and speed
requirements. These requirements translate into a variety of modes of moving data
from one place to another.
Data in a WavePhore network are transmitted and received in one of three modes: as
transparent synchronous, transparent asynchronous, or statistically-multiplexed
data.
Transparent
Sync and
Async Data Transparent synchronous and asynchronous modes refer to the data link protocol by
which the originating source sent the data to the TDM. The time-division multiplexer
at the NCC
head-end assembles those data into the aggregate data stream without
applying additional processing or overhead to the message. Likewise, on the receiver
side, the transparent synchronous and asynchronous data move through an output
port without additional processing. These modes of data transmission either require
no processing to display coherently, or assume that any processing required is
handled by a computer application at the end-user’s site.
If the CPU partition of the aggregate data stream coming from the TDD is
transparent asynchronous, only Serial 1 can be used as an output (see Figure 5-2
and Table 5-1.)