Comtech EF Data CDM-625, Инструкция по установке и эксплуатации

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CDM-625 Advanced Satellite Modem Revision 1
Forward Error Correction Options MN-0000036 (Ref MN/CDM625.IOM)
Table 7-5. Comparison of all Comtech EF Data TPC and LDPC Modes (CDM-625 with
LDPC/TPC Codec)
Mode
Eb/No at
BER = 10
-6
(typical)
Eb/No at
BER = 10
-8
(typical)
Spectral
Efficiency
(bps per
Hertz)
Symbol Rate
Occupied *
Bandwidth
for 1 Mbps
Carrier
QPSK Rate 1/2 Viterbi * 5.5 dB 6.8 dB 1.00 bps/Hz 1.0 x bit rate 1190 kHz
BPSK Rate 1/2 LDPC 1.7 dB 1.9 dB 0.50 bps/Hz 2.0 x bit rate 2380 kHz
BPSK Rate 21/44 TPC 2.8 dB 3.0 dB 0.48 bps/Hz 2.1 x bit rate 2493 kHz
BPSK Rate 5/16 TPC 2.4 dB 3.0 dB 0.31 bps/Hz 3.2 x bit rate 3808 kHz
QPSK/OQPSK Rate 1/2 LDPC 1.7 dB 1.9 dB 1.00 bps/Hz 1.0 x bit rate 1190 kHz
QPSK/OQPSK Rate 21/44 TPC 2.8 dB 3.3 dB 0.96 bps/Hz 1.05 x bit rate 1246 kHz
QPSK/OQPSK Rate 2/3 LDPC 2.1 dB 2.4 dB 1.33 bps/Hz 0.75 x bit rate 892 kHz
QPSK/OQPSK Rate 3/4 LDPC 2.7 dB 2.9 dB 1.50 bps/Hz 0.67 x bit rate 793 kHz
QPSK/OQPSK Rate 3/4 TPC 3.4 dB 4.0 dB 1.50 bps/Hz 0.67 x bit rate 793 kHz
QPSK/OQSK Rate 7/8 TPC 4.2 dB 4.3 dB 1.75 bps/Hz 0.57 x bit rate 678 kHz
QPSK/OQPSK Rate 0.95 TPC 6.0 dB 6.5 dB 1.90 bps/Hz 0.53 x bit rate 626 kHz
8-PSK Rate 2/3 TCM **
and RS (IESS-310)
5.6 dB 6.2 dB 1.82 bps/Hz 0.56 x bit rate 666 kHz
8-QAM Rate 2/3 LDPC 4.3 dB 4.6 dB 2.00 bps/Hz 0.50 x bit rate 595 kHz
8-QAM Rate 3/4 LDPC 4.7 dB 5.0 dB 2.25 bps/Hz 0.44 x bit rate 529 kHz
8-PSK/8-QAM Rate 3/4 TPC 6.1 dB 6.7 dB 2.25 bps/Hz 0.44 x bit rate 529 kHz
8-PSK/8-QAM Rate 7/8 TPC 6.7 dB 6.9 dB 2.62 bps/Hz 0.38 x bit rate 453 kHz
8-PSK/8-QAM Rate 0.95 TPC 9.2 dB 10.2 dB 2.85 bps/Hz 0.35 x bit rate 377 kHz
16-QAM Rate 3/4 LDPC 6.7 dB 6.8 dB 3.00 bps/Hz 0.33 x bit rate 396 kHz
16-QAM Rate 3/4 TPC 7.4 dB 8.1 dB 3.00 bps/Hz 0.33 x bit rate 396 kHz
16-QAM Rate 7/8 TPC 7.9 dB 8.1 dB 3.50 bps/Hz 0.28 x bit rate 340 kHz
16-QAM Rate 3/4 **
Viterbi/Reed-Solomon
7.5 dB 8.0 dB 2.73 bps/Hz 0.37 x bit rate 435 kHz
16-QAM Rate 7/8 **
Viterbi/Reed-Solomon
9.0 dB 9.5 dB 3.18 bps/Hz 0.31 x bit rate 374 kHz
* 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:
7–8