MN.00356.E - 003 23
• InBand/OutOfBand management
• Power over Ethernet or dedicated power feeders
• full featured future proof CE switch
• future proofs unified architecture and OS software platform.
5.7.1 ACM
SIAE MICROELETTRONICA implements MSE based Adaptive Coding and Modulation in all channel band-
widths.
Multiple ACM profiles are available for automatic changes in accordance with the link conditions and select-
ed parameters (highest modulation, lowest modulation, masks, power mode etc.). ACM together with QoS
fits perfectly with modern networks requirements in order to ensure the high priority traffic to be never
dropped even in the worst conditions.
ACM includes modulation schemes starting from 4QAM to 4096QAM. Additional sets of ACM profile are in-
cluded differentiating between two different FEC rate codes maximizing throughput, system gain and link
availability with the same constellation type, just changing on-fly the ratio between payload bits and pro-
tection bits in the FEC ratios. This unique set of profiles allows achieve –at the same time– higher capacity
in good propagation conditions and really higher signal strength in tough propagation conditions.
ACM feature is available in all the configurations (1+0/1+1/2+0/4+0 and XPIC). Note that ACM works in-
dependently for uplink and downlink and it is able to protect against fading up to 100dB per second.
In order to configure properly the radio link using ACM facility, an optimization must be found between
max traffic during good propagation conditions and max availability during bad propagation conditions. To
obtain this purpose the ACM can be configured via software.
ACM setting
The ACM can vary modulation profiles between two extremes defined by the operator through software
configuration: Upper modulation and Lower Modulation.
• Upper modulation - When propagation into the given radio channel is in the better condition (high
RX S/N), the radio link is working at the maximum throughput defined at Upper Modulation: the
highest modulation profile that ACM can employ
• Lower modulation - When propagation into the given radio channel is the worst channel in the worst
condition (low Rx S/N), the radio link is working at the minimum throughput, defined at Lower Mod-
ulation: the lowest modulation profile that ACM can employ.
ATPC and ACM interaction
The Automatic Transmission Power Control (ATPC) regulates the RF output power of the local transmitter
depending on the value of the RF level at the remote terminal. This value has to be preset from the local
terminal as threshold high and low. The difference between the two thresholds must be equal or higher
than 3 dB.
As soon as the received level crosses the preset Low Level threshold due to the increase of the hop atten-
uation, a microprocessor (μP) sends back to the local terminal a control to increase the transmitted power.
A good set of the thresholds is to put the ATPC Low Level threshold higher than the downshift threshold of
the highest modulation scheme of the ACM; this way, the ATPC start to work before than the downshift.
The behaviour of the system is to try to increase the PTx and so the System Gain, before than being forced
to reduce capacity due to modulation downgrade.
Resuming, the correct setting of the thresholds is when the two windows, the ATPC one and the ACM one,
are not overlapped.
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