L3 Communications MPM-1000A Operator's Manual page 93

MPM-1000A Operator Manual
Terminal usage and Satellite resources by using a large set of adaptive data-rates (in
approximately 1.5 dB steps), code-rates, modulation types, spread factors, adaptive
power-control (in 0.25 dBW increments) and the use of multiple simultaneous
transmitters and receivers at each Terminal.
The NC schedules within the constraints of the total available power and spectrum at
the Satellite BW-segments of operation and the total available power and power-control
dynamic range at each Terminal. The NC accounts for all transmissions in the network,
and ascertains at any instance in time that the total power out of the Satellite does not
exceed the Satellite Effective Isotropic Radiated Power (EIRP) allocation and the
occupied spectrum does not exceed the allocated BW. The NC also ensures that the
total Terminal power is not exceeded across multiple modulators and that the Terminal
can implement the assigned Terminal EIRP. The NC schedules based on data priority,
jitter and the following:
Bit Error Rate (BER) requirement – each burst must achieve the required Carrier
to Noise Ratio (C/No) at the receiving Terminal‟s Modem for the given burst
mode.
Effective Isotropic Radiated Power (EIRP) density requirement – each burst must
be spread to meet the power-density Decibels Watts per Hertz (dBW/Hz)
requirement for the given Terminal aperture size when operating over densely
spaced Satellites.
The NC predicts the total C/No at the destination for each link (NC to NM, NM to NC,
NM to NM), given the EIRP at the transmitting Terminal, the uplink path loss, the
transfer gain and G/T of the Satellite BW segment, the downlink path loss, and the G/T
at the receiving Terminal. The NC selects adaptive burst parameters based on the
predicted C/No at the destination; the uplink and downlink spread requirements and
Satellite/Terminal resource constraints.
The NC computes and maintains uplink and downlink path loss values for each
Terminal, including itself. The NC computes its own path loss values by first computing
the clear-sky path losses based on Terminal and Satellite position and its BW segment
uplink and downlink frequencies. The NC then computes a predicted clear-sky C/No
based on the clear-sky path losses, the Terminal EIRP value, the Satellite parameters
and the Terminal G/T. The NC compares the actual C/No (as reported by the Modem
based on the FOW reception) with the predicted clear-sky C/No to compute the actual
path loss values.
The NC computes downlink path loss values for NMs using the actual FOW C/No
values measured by the NM (reported in the AROW to the NC) along with the NC FOW
EIRP, the NC uplink path loss, the Satellite parameters (G/T and SFD), and the NM
receive G/T. The NC computes uplink path loss values for NMs using the actual AROW
C/No measured by the NC along with the NM AROW EIRP, the Satellite parameters
(G/T and SFD), the NC downlink path loss, and the NC receive G/T.
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