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CDM-625A Advanced Satellite Modem
Introduction
•
It now supports a more complete range of transmit filter options (spectrum shaping).
Transmit alphas of 0.05, 0.10, 0.15 0.20, 0.25 and 0.35 are included, which in turn
permits the user to reduce channel spacing as transmit alpha (and hence occupied
bandwidth) reduces, providing potentially significant gains in transponder bandwidth
efficiency.
•
Like the CDM-625, its demod design incorporates fast acquisition, improved composite
power handling, and an integrated adaptive equalizer.
•
It includes VersaFEC Adaptive Coding and Modulation in the base hardware to increase
capacity on IP links.
•
It includes DoubleTalk
separate plug-in card. (However, FAST codes are still required to activate this option.)
•
It can be equipped with an optional IP Packet Processor card that, in addition to providing
Layer 3 functionality, incorporates a number of key features for Wide Area Network
(WAN) bandwidth optimization: very low overhead Streamline Encapsulation (SLE),
Header and Payload Compression, Advanced Quality of Service (QoS), and Advanced
Encryption Standard (AES) Encryption.
•
IEEE-1588v2 Precision Timing Protocol (PTP) and Jumbo Frame Support are available
options.
•
It has two internal expansion slots that are available for future FEC options, etc. The new
base hardware includes sufficient FPGA and memory resources to permit Comtech EF
Data to continue to update the capability of the modem as new technologies emerge.
1.2
Functional Description
The CDM-625A has two fundamentally different types of interface - IF and data:
•
The IF interface provides a bidirectional link with the satellite via the uplink and
downlink equipment.
•
The data interface is a bidirectional path that connects with the customer's equipment
(assumed to be the DTE) and the modem (assumed to be the DCE).
Transmit data is received by the terrestrial interface where line receivers convert the clock and
data signals to CMOS levels for further processing. A small FIFO follows the terrestrial interface
to facilitate the various clocking and framing options. If framing is enabled, the transmit clock
and data output from the FIFO pass through the framer, where the overhead data (IDR, IBS, D&I
or EDMAC) is added to the main data; otherwise, the clock and data are passed directly to the
Forward Error Correction encoder.
See Appendix S. TRANSMIT SPECTRUM FILTERING OPTIONS for important
information about these new options.
®
Carrier-in-Carrier
®
in the base hardware, and no longer requires a
1–2
Revision 0
MN-CDM625A
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