Comtech EF Data SLM-5650B, Installation And Operation Manual

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SLM-5650B Satellite Modem
Revision 2
Appendix E E–4 MN-SLM-5650B
E.3 Sources of Overhead
E.3.1 Framing Overhead
Several modes of operation add framing overhead to the satellite channel.
IBS and IDR framing are also technically supported in the SLM-5650B, in that
these framing modes can be enabled. However, the overhead channel
information associated with these framing modes is not available external to the
modem in either transmit or receive directions. These framing modes therefore
are of limited use in the SLM-5650B, and are not included for consideration in
this appendix.
E.3.1.1 Reed–Solomon/Outside FEC Codec Framing Factor
The overhead factor of this feature is referred to as “Operand 3” in Section E.2:
•
Reed–Solomon can be appended with the Viterbi FEC, but it is only supported in
the MIL-165A and IESS modem type configurations. The Reed–Solomon error
correction is user selectable to operate within a set of predefined legacy formats.
E.3.1.2 AUPC/ASYNC (ESC) and ACPC Channel Framing
AUPC/ASYNC overhead channel
and the ACPC framing factor are referred to as
“Operand 4” in Section E.2:
•
The AUPC/ASYNC overhead channel supports an EIA-232 or EIA-422 overhead
channel that is asynchronous to the main traffic channel. This legacy communications
channel also supports modem-to-modem receiver signal Eb/No status used to
automatically adjust the Tx uplink power when (AUPC Power Control) is enabled. If the
AUPC framing mode is enabled, 16 framed output bits are created for every 15 input bits
of the transport stream regardless if the features are being used. The AUPC/ASYNC
overhead factor is a function of the programmed Data Rate.
•
The Automatic CnC Power Control (ACPC) overhead frame provides modem-to-
modem receiver CnC signal status required to implement the CnC ratio balancing ACPC
algorithm. When this feature is enabled, 32769 framed output bits are generated for
every 32605 input bits of the transport stream.
ASYNC/AUPC and ACPC communications framing are mutually
exclusive features. You may not enable these features simultaneously.