Comtech EF Data CDD-880, Installation And Operation Manual

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CDD-880 Multi Receiver Router MN-CDD880
Appendix G Revision 2
G–12
•
Further, as C/N increases, MODCOD is adjusted, first leaving power at maximum until quality
indicates reduction in power. Such reduction represents the terminal power control
operating without hub backoff information, preventing power from increasing beyond
margin.
Figure G-5 depicts Dynamic Power Control operating with ACM.
Figure G-5. DPC with ACM at Rate Max Power
G.3.2.1 Terminal Maximum Power
Terminal Maximum Power is achievable only if the remote terminal has information on the hub
end environmental conditions, and the remote end’s gain compression point (P1dB) is
determined. If the hub can relay downlink information for clear-sky or degraded signal quality,
the remote terminals are allowed to increase their power beyond the Rate Maximum Power
setting.
Terminal Maximum Power Control operates using a hub-generated outbound Universal
Announcement (UA) message, which is broadcast to all listening remotes on timed intervals. The
UA message that is generated and sent by the CTOG-250 contains an attenuation value and
other network routing information. This attenuation value is a number is from 0 to 799, with the
CDM-805 indicating invalid/”no attenuation” information. Each remote operating in DPC mode
cannot increase power greater than Rate Maximum Power unless the hub’s attenuation
message represents a value less than or equal to the Terminal Maximum Power setting.
For example, see
Figure G-6
. If the remote Rate Maximum Power is –15 dBm with a Terminal
Maximum Power setting of -5 dBm and the hub attenuation is 0 dB, then the remote may
increase its power up to +10 dB without violating its PEB or link budget Service Level Agreement
(SLA). This is possible because, if the hub is indicating clear-sky (UA=0 dB), the only contribution
of reported low E
s
/N
0
is Attenuation ‘A’ (between the remote transmit uplink and the satellite).
If the UA were to indicate a value other than 0 dB, then for Attenuation ‘B’ at the downlink, the
terminal would add this value to the GCP backoff, reducing the terminal maximum power.
Note
that terminal maximum power is with MODCOD backoff applied.