End-To-End Processing Delay; Table 7-5. Comparison Of All Comtech Ef Data Tpc And Ldpc Modes (Cdm-625 With Ldpc/Tpc Codec) - Comtech EF Data CDM-625 Installation And Operation Manual

CDM-625 Advanced Satellite Modem
Forward Error Correction Options
Table 7-5. Comparison of all Comtech EF Data TPC and LDPC Modes (CDM-625 with
Mode
QPSK Rate 1/2 Viterbi *
BPSK Rate 1/2 LDPC
BPSK Rate 21/44 TPC
BPSK Rate 5/16 TPC
QPSK/OQPSK Rate 1/2 LDPC
QPSK/OQPSK Rate 21/44 TPC
QPSK/OQPSK Rate 2/3 LDPC
QPSK/OQPSK Rate 3/4 LDPC
QPSK/OQPSK Rate 3/4 TPC
QPSK/OQSK Rate 7/8 TPC
QPSK/OQPSK Rate 0.95 TPC
8-PSK Rate 2/3 TCM **
and RS (IESS-310)
8-QAM Rate 2/3 LDPC
8-QAM Rate 3/4 LDPC
8-PSK/8-QAM Rate 3/4 TPC
8-PSK/8-QAM Rate 7/8 TPC
8-PSK/8-QAM Rate 0.95 TPC
16-QAM Rate 3/4 LDPC
16-QAM Rate 3/4 TPC
16-QAM Rate 7/8 TPC
16-QAM Rate 3/4 **
Viterbi/Reed-Solomon
16-QAM Rate 7/8 **
Viterbi/Reed-Solomon
* The occupied bandwidth is defined at the width of the transmitted spectrum taken at the –10 dB
points on the plot of power spectral density. This equates to 1.19 x symbol rate for the CDM-625
transmit filtering.
** Included for comparative purposes

7.6.3 End-to-End Processing Delay

In many cases, FEC methods that provide increased coding gain do so at the expense of increased
processing delay. However, with TPC, this increase in delay is very modest. Table 7-6 shows, for
the CDM-625, the processing delays for the major FEC types, including the three TPC modes:
LDPC/TPC Codec)
Eb/No at Eb/No at
-6
BER = 10 BER = 10
(typical) (typical)
5.5 dB 6.8 dB
1.7 dB 1.9 dB
2.8 dB 3.0 dB
2.4 dB 3.0 dB
1.7 dB 1.9 dB
2.8 dB 3.3 dB
2.1 dB 2.4 dB
2.7 dB 2.9 dB
3.4 dB 4.0 dB
4.2 dB 4.3 dB
6.0 dB 6.5 dB
5.6 dB 6.2 dB
4.3 dB 4.6 dB
4.7 dB 5.0 dB
6.1 dB 6.7 dB
6.7 dB 6.9 dB
9.2 dB 10.2 dB
6.7 dB 6.8 dB
7.4 dB 8.1 dB
7.9 dB 8.1 dB
7.5 dB 8.0 dB
9.0 dB 9.5 dB
7–8
MN-0000036 (Ref MN/CDM625.IOM)
Spectral
Efficiency
-8
Symbol Rate
(bps per
Hertz)
1.00 bps/Hz 1.0 x bit rate
0.50 bps/Hz 2.0 x bit rate
0.48 bps/Hz 2.1 x bit rate
0.31 bps/Hz 3.2 x bit rate
1.00 bps/Hz 1.0 x bit rate
0.96 bps/Hz 1.05 x bit rate
1.33 bps/Hz 0.75 x bit rate
1.50 bps/Hz 0.67 x bit rate
1.50 bps/Hz 0.67 x bit rate
1.75 bps/Hz 0.57 x bit rate
1.90 bps/Hz 0.53 x bit rate
1.82 bps/Hz 0.56 x bit rate
2.00 bps/Hz 0.50 x bit rate
2.25 bps/Hz 0.44 x bit rate
2.25 bps/Hz 0.44 x bit rate
2.62 bps/Hz 0.38 x bit rate
2.85 bps/Hz 0.35 x bit rate
3.00 bps/Hz 0.33 x bit rate
3.00 bps/Hz 0.33 x bit rate
3.50 bps/Hz 0.28 x bit rate
2.73 bps/Hz 0.37 x bit rate
3.18 bps/Hz 0.31 x bit rate
Revision 1
Occupied *
Bandwidth
for 1 Mbps
Carrier
1190 kHz
2380 kHz
2493 kHz
3808 kHz
1190 kHz
1246 kHz
892 kHz
793 kHz
793 kHz
678 kHz
626 kHz
666 kHz
595 kHz
529 kHz
529 kHz
453 kHz
377 kHz
396 kHz
396 kHz
340 kHz
435 kHz
374 kHz