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QMultiFlex-400™ Installation and Operating Handbook
6.2.22.7 ACM Mode
Off
No ACM data is sent or received.
On
ACM data is sent and received via a bi-directional IP link. The Es/No
information is inserted into the carriers with no material effect on
bandwidth. When ACM is on Es/No data is expected, which is used to
dynamically match the transmitting MODCOD to suit the current
conditions. Carrier symbol rate and power remain unchanged, but data
rate will vary with the choice of MODCOD.
With many remotes reporting their Es/No back, the QMultiFlex-400™ will
always act upon the lowest Es/No.
Monitor
ACM data is sent and received, but no action is taken to change the
transmitting MODCOD. This setting would be selected if it was desired
that ACM should only work in one direction - the modem with 'monitor'
selected would be the side of the link that does not change the MODCOD.
Note: The remote modems stream identifier needs to be the same number as the
demodulator when ACM is 'On' at the remotes. i.e. Remote modem 1 needs to have stream
ID of 1, Remote modem 2 needs to have stream identifier of 2 etc.
details on ACM system configuration.
6.2.22.8 ACM Rain Fade Margin
Range:
0dB to 9.9dB; step size: 0.1dB
Description:
This sets a margin used in the ACM control process when making
decisions on what MODCOD to select based on the current Es/No
reading of the remote modem(s). By setting the ACM rain fade margin to
a non-zero value, ACM operation will cope with a faster rate of rain fade
without losing demodulator lock than would otherwise be the case.
Note that the ACM control process has its own non-configurable
operating margin built in (which will cope with Es/No changes of up to
1dB/s) and therefore the ACM rain fade margin should be used only on
links that have the potential for particularly severe rain fades.
Setting an ACM margin that is higher than necessary will reduce the
benefits of using ACM since non-optimal MODCODs may be used due
to the need to maintain a larger margin between the actual Es/No and
the Es/No required by the dynamically selected MODCODs.
Table 6-36 ACM Control Options
Table 6-37 ACM Rain Fade Margin
6-53
See section 8.2
for more
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