ViaSat ArcLight, User Manual, Page: 282 / 368

ArcLight Hub User’s Guide
Component Operating Procedures
5-30 1081006 Rev. 001
5.10 Multi-Channel Demodulator II (MCD II)
5.10.1 Overview
The ArcLight Multi-Channel Demodulator II (MCD II) terminates the
spread return links at the hub of an ArcLight satellite network as
shown in Figure 1-3. It is installed as a series of blade servers within
the ArcLight Blade System. Figure 5-21 shows the server layout on the
front of the ABS chassis and Figure 5-22 shows the rear server layout
of the ABS chassis.
The MCD resides as blades within the ABS.
The MCD II performs the following functions:
1. Receives multiple Gaussian Minimum Shift Keying (GMSK)
modulated waveforms on a 70 MHz IF carrier on the RX IF input
2. Detects, Demodulates, and decodes frames of modulated data
3. Reassembles the data frames into IP packets
4. Forwards reassembled IP packets to the hub data router
5. Collects link statistics for each IP packet received, and forwards
them to the Real-Time Network Management System (RtNMS)
The MCD is configured and monitored by the NMS using SNMP.
Reassembled IP data packets are sent to the hub data router over
MCD’s 100BaseT Ethernet port (LAN 1). For each reassembled IP
packet, a Link Status packet is sent to the RtNMS over a separate
dedicated 100BaseT Ethernet MCD port (LAN 2).
An MCD II as shown in Figure 5-21 consists of:
1. One 10U 19-inch rack-mountable chassis.
2. Three compactPCI (cPCI) hot-swappable N+1 redundant power
supplies.
3. Two (2) Monitor and Control (M&C) system cards in physical
chassis slots 8 and 9. The cards perform IP packet reassembly
and forwarding and also provide configuration and management
for the entire chassis.
4. One Watchdog Alarm Module (WAM) card in physical chassis
slot 10. This card controls chassis LEDs and provides
environmental data.
5. Two Utility Cards (UCs) in physical chassis slots 1 and 2. Each
Utility Card is paired with corresponding M&C card to make a
cold redundant pair. The UCs provide the 93Mhz reference clock
to the Correlator-Demodulator Cards.
6. Up to ten (10) Correlator-Demodulator cards (CDCs) providing
return channel demodulation. Each card can provide a single
return channel or multiple cards can be chained together to add
capacity to a return channel.
The Ethernet ports connect through the backplane of the ABS. The
Ethernet ports on the front of the M&C cards are not used (?? Still
true??).