Adaptive Coding & Modulation (Acm); Introduction - Teledyne QMultiFlex-400 Installation And Operating Handbook

QMultiFlex-400™ Installation and Operating Handbook
5. Record the remote Eb/No under clear-sky conditions and then set the AUPC mode
to maintain the remote Eb/No.
6. Set a target Eb/No and set the maximum power level.
7. Review the remote Eb/No to confirm that it is being maintained correctly under
different atmospheric conditions. The web user interface remote Eb/No and power
graphs can be used to review AUPC performance.
Note: AUPC is limited to a single QMultiFlex-400™ unit i.e. up to 16 remotes. Cascaded
units are not currently supported. There are other limitations with this feature in a Point to
Multipoint system. Contact support for more information.
8.2 Adaptive Coding & Modulation (ACM)
8.2.1

Introduction

As an alternative to AUPC, ACM can be used to dynamically adapt the MODCOD of the
link to better suit changing conditions. A standard DVBS2X link would have a rain-fade
margin built into the link budget (typically around 3dB above QEF point of MODCOD used).
Instead of running high rain-fade margins 100% of the time, ACM can be used with a
minimal rain-fade margin with a larger throughput. More efficient higher order MODCODS
can be used in clear sky conditions and if conditions change, the MODCOD will adjust to a
lower order one to maintain link continuity.
ACM can be used in a star topology one-way (Outbound or Inbound) or in bidirectional
VCM mode.
One-Way: Outbound ACM
HUB Modem
ACM setting: On
Transmit MODCOD changes
based on worst remote
Es/No (Remote stream IDs
the same value)
HUB only displays worst
Es/No in ACM Status screen.
Degradation position 1: Hub transmit MODCOD changes and reduces throughput for all
remote modems, which ensures system continuity. Return carriers are degraded, hopefully
within a rain fade margin.
Degradation position 2: Hub transmit MODCOD changes and reduces throughput for whole
system based on one remote location. A return carrier gets degraded, hopefully within a
rain fade margin.
Note: The receiving MODCOD with maximum possible throughput information can be seen
on the Status (ACM) screen of the modem.
1
Figure 8-1 ACM One-Way - Outbound
8-2
Remote Modems
ACM setting: Monitor Mode.
All Stream IDs set to the
same number.
Remote modems reporting
back Es/No information, but
not adjusting
MODCOD.
2
Transmit