Comtech EF Data CDM-760, Инструкция по установке и эксплуатации

Страница: 131 / 441

Front Panel Operation Revision 4
CDM-760 Advanced High-Speed Trunking Modem MN-CDM760
6–42
6.2.2.5.2 (CONFIG: CnC) Min / Max Search Delay
To reduce the time taken for the CnC algorithm to converge, you can restrict the range of delay
the search uses. Factory default values for satellite operation are set to a minimum of 230 ms
and a maximum of 290 ms. Once CnC has found the exact delay the value can be further
reduced, but care should be taken to allow sufficient range to accommodate changes in path
delay due to Doppler.
To change the CnC Min or Max Search Delay: Use the   arrow keys to select the delay number
to edit using the arrow keys, and then edit the value of each number by using the

arrow
keys. Press ENTER .
If CnC is being bench-tested with two units in a back-to-back configuration, the
minimum delay should be set to 0 ms, and the maximum to 20 ms. This takes into
account the lack of satellite delay.
6.2.2.6 CONFIG: Comp
K4 GZip Lossless Compression and Decompression is an optional feature that requires
installation of the Compression Card in the modem.
Compression: Disabled
Decompression: Disabled (


)
Use the   arrow keys to select a parameter. Press ENTER .
6.2.2.6.1 (CONFIG: Comp) Compression
Compression enables or disables the Tx compression path (LAN to Satellite). Tx Compression
(LAN to Satellite) requires activation of this FAST Option. Tx compression rate FAST Options may
be purchased and activated by the symbol rate, so maximum data rates will depend on
modulation and coding schemes used.
The CDM-760 uses a very fast, hardware-based (FPGA and ASIC) compression engine. In
most cases you do not need to worry about any limitations of the compression engine.
If, however, you are running a very high speed link and you are running exclusively
small Ethernet Frames in non-Packet Processor mode, or small IP datagrams with the
optional High-Speed Packet Processor card, refer to this table for the maximum
limitations of the compression engine:
Ethernet Frame Size
(bytes)
Limitation
Frames/Second
Limitation
Data Rate at
Limitation (Mbps)
64 Frames/Second 293,000 150
128 Frames/Second 293,000 300
>133 Modem Data Rate N/A 314