ViaSat ArcLight, Руководство пользователя, Страница: 44 / 368

ArcLight Hub User’s Guide
General System Description
1-8 1081006 Rev. 001
Figure 1-4. Generic ArcLight Hub Interfaces.
The uplink power control algorithm implemented jointly by RtNMS and
the VMT controls the transmit power of the VMTs and provides fair
network access.
The ViaSat Forward Link Modulator (VFLM) provides for the request
and delivery of broadband IP data to a collection of subscriber terminals
within a STAR satellite network.
To recover the return channel, the ArcLight system features two ViaSat-
proprietary technologies: Code Reuse Multiple Access (CRMA) and
Asymmetric Paired Carrier Multiple Access (A-PCMA).
FLM
The FLM interfaces to the network on the hub side over a 10/100 base-
T Ethernet interface and outputs an RF signal at a 70MHz IF. The FLM
IF is connected to a PCMA Hub Canceller and simultaneously a Ku-
band upconverter or an uplink power control device.
The MCD-II receives and Demodulates the spread spectrum bursts
from the VMTs then re-assembles IP packets from the ATM cells it
has Demodulated and decoded. The MCD II has several Correlator-
Demodulator-Cards (CDC) that receive, unspread and Demodulate
incoming traffic bursts from the VMTs. Each CDC has one
correlator and twelve Demodulators. All the CDCs communicate
with the rest of the hub equipment through the System Controller
and a utility card (UC) supplies analog signal processing and clock
distribution for the MCD-II.
The UC-II performs several functions for MCD-II. It filters the IF
input and provides enough amplification to overcome the losses
incurred in the 10-way splitter. The UC-II also receives the 10 MHz