Comtech EF Data DMD1050TS, Инструкция по установке и эксплуатации

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DMD1050TS Satellite Modem Board
Revision 1
Appendix I I–1 MN-DMD1050TS
Appendix I. Information
Throughput Adaptation (ITA)
Operation
I.1 Information Throughput Adaptation (ITA) Operation
ITA, also known as Adaptive Coding and Modulation (ACM), allows the DMD1050TS to mitigate
downlink rain-fades by means of adapting the throughput of the modem effectively decreasing the
modulation and coding by fixing the symbol rate and changing data rate to keep a constant power
spectral density. When ITA is operating using the DMD1050TS partner modem indicates the
highest possible data rate constrained to a fixed symbol rate.
ITA turns fade margin into increased link capacity – gains of 100% or more are possible,
compared to traditional static Frequency Division Multiple Access (FDMA) links. This is
accomplished by automatically adapting the modulation type and FEC code rate to give highest
possible information throughput. ITA maximizes throughput regardless of link conditions (noise or
other impairments, clear sky, rain fade, etc). Initial setup is easy, and then requires no further
user intervention. With a static traditional FDMA system, severe rain fading can cause the total
loss of the link, and zero throughput. ITA keeps the link up (with lower information throughput) –
and can yield much higher system availability. ITA in the DMD1050TS used in conjunction with
the EBEM framing unit adjusting the IP traffic in either IP Only or mixed serial IP mode.
I.1.1 Properties of ITA on the DMD1050TS
•
The DMD1050TS output power remains constant before, during, and after state changes.
•
The DMD1050TS output spectral density remains constant before, during, and after state
changes.
•
When ITA is enabled, the DMD1050TS will automatically constrain the dynamic bit rate to
conform to the limitations of the terrestrial interface that is selected for use in the
DMD1050TS configuration.
•
ITA can only be enabled when the DMD1050TS is operating in the EBEM mode.
•
Operation of ITA and AUPC are mutually exclusive, both cannot be active at the same
time.
•
The code rate block size will remain fixed for the duration of the ITA operation,
independent of the bit rate.
•
When the link is set up for ITA, the symbol rate is entered by the operator, at a resolution
of 1 sps. The DMD1050TS will automatically calculate the data rate.
•
The embedded channel is used for exchanging ITA messages between DMD1050TS
modems.