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CDM-600L Satellite Modem
Introduction
1.1
Standard Features
The CDM-600L provides a wealth of standard features which go far beyond the basic
requirements of the Intelsat specifications.
In Closed Network applications, to facilitate network management, the CDM-600L
incorporates EDMAC, an acronym for Embedded Distant-end Monitor And Control. In
this mode, an additional 5% overhead is combined with the traffic data, (1.5% in Turbo
BPSK modes, Turbo Rate 1/2 QPSK/Offset QPSK, and all data rates greater than 2
Mbps) which permits M&C information to be added (transparently to the user), allowing
access to the distant-end modem. This mode does not require any additional cabling at
either the local or distant-end Modems - access to EDMAC is via the standard M&C
control port. Full monitor and control is possible, and importantly, the on/off status of the
carrier at the distant-end carrier can be controlled.
The standard TX-IF port has a Type N female connector with 50Ω impedance.
1.1.1
AUPC
An important innovation in the CDM-600L is the addition of Automatic Uplink Power
Control (AUPC). This feature enables the modem to automatically adjust its output
power to maintain the Eb/No of the remote end of the satellite link constant. This
provides protection against rain fading, a particularly severe problem with Ku-band links.
To accomplish this, the framed (EDMAC) mode of operation must be used, and the
distant end modem constantly sends back information about the demodulator Eb/No
using reserved bytes in the overhead structure. Using the Eb/No, the local modem then
adjusts its output power, and hence, a closed-loop feedback system is created over the
satellite link.
A benefit of this feature is that whenever EDMAC/AUPC operation is selected, the
remote demodulator's Eb/No can be viewed from the front panel display of the local
modem. Observe that both EDMAC and AUPC can be used simultaneously.
1.1.2
Software – Flash Upgrading
The internal software is both powerful and flexible, permitting storage and retrieval of up
to 10 different modem configurations. The modem uses 'flash memory' technology
internally, and new firmware can be uploaded to the unit from an external PC. This
simplifies software upgrading, and updates can now be sent via the Internet, e-mail, or on
disk. The upgrade can be performed without opening the unit by simply connecting the
modem to the serial port of a computer.
1–2
Revision 0
MN/CDM600L.IOM
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