Comtech EF Data cdm-570a - Configuring Versafec ACM

CDM-570A/570AL Satellite Modem with Optional Packet Processor
Revision 5
Adaptive Coding and Modulation (ACM) Option P–10 MN-CDM570A
P.6.2 Configuring VersaFEC ACM
Chapter 6. FRONT PANEL OPERATION
VersaFEC ACM requires the appropriate FAST code for the maximum
operating symbol rate.
The ACM system is designed to switch based on thresholds that correspond to a
BER of 5 x 10
-8
for each ModCod. However, in order to prevent oscillation around
two ModCods at this exact value, 0.3 dB of hysteresis has been added.
Do these steps to configure the CDM-570A/570AL for VersaFEC ACM operation from the
CDM-570A/570AL front panel:
Step
Task
Front Panel VFD Mnemonic
1
(SELECT) CONFIG: TI
Use the ◄ ► arrow keys to select a parameter. Press
ENTER to set the mode as IP-ACM.
Data Intf: RS422 IP V.35
RS232 G703 IP-ACM V2-ACM
2
(SELECT) CONFIG: TI  IP-ACM  ACM
Use the ◄ ► arrow keys to select a parameter. Press
ENTER to set the mode as
• ModCod
• Unlock-Action
• Target-SNR-Margin
ACM:ModCod Unlock-Action
Target-SNR-Margin
2a.
(SELECT) CONFIG: TI  IP-ACM  ModCod
Use the ◄ ►arrow keys to select the Min(imum) (on the
top line) or Max(imum) ModCod range setting (on the
bottom line). Then, use the ▲▼ arrow keys to define
the range of ModCods (00-11) over which the system will
operate. Press ENTER.
ModCod 00 is BPSK Rate 0.488 (0.49 bps/Hz), while
ModCod 11 is 16-QAM Rate 0.853 (3.41bps/Hz).
Min Modcod: 00 BPSK .488
Max Modcod: 11 16QAM .853
To constrain the system to run at a fixed ModCod, set the Min and Max ModCod values to
be equal.
The value of Max ModCod may be limited by other FAST codes installed. For example,
suppose the 4100 ksps FAST option is installed, and the symbol rate set to 4100 ksps,
the theoretical maximum data rate would be 14 Mbps at ModCod 11. However, if CnC is
being used, with a 10 Mbps FAST limit the ACM Max ModCod will be limited to ModCod
7, or 9.6 Mbps.
2b.
(SELECT) CONFIG: TI  IP-ACM  Unlock-Action
Use this submenu to establish the desired action when
the remote demod loses lock. This is important, as the
ACM system depends on the feedback of the SNR metric
from the remote demod to determine the optimum
ModCod. Use the ▲▼ arrow keys to select Go to min
Tx ModCod (recommended) or Maintain Tx ModCod.
Press ENTER.
Distant-end loses lock:
Go to min Tx ModCod(▲ ▼)