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CDM-625 Advanced Satellite Modem
Adaptive Coding and Modulation (ACM)
•
Latency for 16k block DVB-S2 ACM at 100 ksps = 349 milliseconds
•
Latency for VersaFEC ACM at 100 ksps = 54 milliseconds
•
•
17.8 Configuring VersaFEC ACM in the CDM-625
VersaFEC ACM requires the correct hardware module (PL-0000264) to be installed
in the CDM-625, Version 1.4.0 (or higher) firmware, and the appropriate FAST code
for the maximum operating symbol rate.
Configuration is very straightforward from the CDM-625 front panel. For a detailed overview of
modem operations via the front panel, refer to Chapter 5. FRONT PANEL OPERATION.
Follow these steps to configure the CDM-625 for VersaFEC ACM operation:
Step
Task
1
(SELECT) CONFIG: MODE
Set the Tx and Rx modes as IP-ACM.
(SELECT) CONFIG: TX SYMB
2
Enter the desired transmit symbol rate. Note that
this is a fundamental departure from the way in
which the modem is typically configured.
(SELECT) CONFIG: TX POWER
3
Enter the desired transmit output level.
(SELECT) CONFIG: RX SYMB
4
Enter the desired receive symbol rate.
Note that asymmetric operation is supported -
transmit and receive symbol rates do not have to be
equal.
(SELECT) CONFIG: ACM
5
Configure the desired ACM operating parameters,
by selecting the ACM submenu from the CONFIG:
menu branch.
Proceeding from the CONFIG: ACM submenu:
For the example shown, the latency for a 16k block DVB-S2 ACM scheme is
approximately 7 times higher than VersaFEC ACM.
The latency for a 64k block DVB-S2 ACM scheme is approximately 25 times
higher than VersaFEC ACM.
The Transmit symbol rate is limited by the FAST code installed.
There are three options:
• 37 ksps to 300 ksps
Front Panel VFD Mnemonic
Mode:Tx=IP-ACM:None Rx=IP-ACM:None
(422,V35,G703s,Audio,LVDS,HSSI,IP,ASI)
Tx-IF Freq Power FEC Mod Symb Scrambler
(Data 00192.000kbps, 00131.657ksps)()
TxSymbolRate = 01000.000 ksps (ACM Mode)
Data Invert=Off Clock Invert=Off
Output Power: Mode= Manual (Fixed)
Level= –20.0 dBm
• 37 ksps to 1200 ksps
RxIF Freq FEC Demod Symb Descram Eq EbNo
(Data 02048.000kbps,02184.533ksps)()
RxSymbolRate = 01000.000 ksps (ACM Mode)
Data Invert=Off Clock Invert=Off
CONFIG: All
Mode Tx
CnC
EDMAC
Misc Mask
ACM Config: Min/Max-ModCod
Target-EbNo-Margin
17–9
Revision 13
MN-CDM625
()
()
• 37 ksps to 4100 ksps
()
Rx
Clocks
ACM
Remote
IP ()
Unlock-Action
()
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