Comtech EF Data CDM-600/600L - Manual (Page 92)

CDM-600/600L Open Network Satellite Modem Revision 3
Front Panel Operation MN/CDM600L.IOM
5–16
5.4.4.2 CONFIG: RX
Æ DECODER
DECODER = VIT (NONE,VIT,SEQ,TCM,TPC,LDPC)
REED-SOLOMON = OFF (ON,OFF)
Select the parameter to edit – Decoder or Reed-Solomon – using the [ ←][→] arrow keys, then
press [ENT].
On the top line, select the parameter to edit using the [ ←][→] arrow keys. The available Decoder
options are shown in the parentheses. Select using the [ ↑][↓] arrow keys, then press [ENT]. The
choices are:
► None (i.e., uncoded) ► TPC (Turbo) (Hardware option)
► Vit (Viterbi) ► LDPC (Hardware option)
► Seq (Sequential)
► TCM ( Trellis Coded Modulation)
8-PSK Rate 2/3 only (FAST option)
Notes:
1. The options of TPC (Turbo) is only displayed if a Turbo Codec is installed.
2. The option of LDPC is only displayed if a TPC/LDPC Codec is installed.
If None is selected for the Decoder setting, the bottom line of the display will change from the
Reed-Solomon selection to a Differential Decoding selection, as shown:
DECODER = NONE(NONE,VIT,SEQ,TCM,TPC,LDPC)
DIFF-DECODER = OFF (ON,OFF)
IMPORTANT
If Differential Encoding=OFF is selected, there is no way for the modem to
resolve the phase ambiguities associated with PSK modulations. For BPSK
there is a 1 in 2 chance that the polarity of the data will be correct. In QPSK
there is a 1 in 4 chance the data will be correct.
When selecting Reed-Solomon On on the bottom line, proceed as follows:
CONFIG: RX
Æ DECODER Æ REED-SOLOMON ON
REED-SOLOMON DECODING = ON(200/180)
Use the [ ↑][↓] arrow keys to select one of the listed parameters, then press [ENT]. Possible
selections, depending on the Framing mode, are as follows:
► IESS-310, open or closed network 219/201
► IBS, open or closed network 126/112
► EDMAC, closed network 200/180
► IDR, open network 225/205 or 194/178
► Unframed closed network:
○ Comtech standard 220/200
○ Legacy EF Data 225/205, with V.35 scrambling