SLM-3650 Satellite Modem
Revision 3
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MN/SLM3650.IOM
A–95
Table A-30.Turbo Product Coding Processing Delay Comparison
FEC Mode (64 kbps data rate)
End-to-end delay, ms
Viterbi, Rate 1/2
12
Sequential, Rate 1/2
74
Viterbi Rate 1/2 + Reed-Solomon
266
Sequential Rate 1/2 + Reed-Solomon
522
Turbo Product Coding, Rate 3/4, {O}QPSK
79
Turbo Product Coding, Rate 21/44, BPSK
64
Turbo Product Coding, Rate 5/16, BPSK
48
Note
: In all cases, the delay is inversely proportional to data rate, so for 128 kbps, the
delay values would be half of those shown above.
It can be clearly seen that the concatenated Reed-Solomon cases increase the delay very
significantly (due mainly to interleaving/de-interleaving), while the TPC cases yield
delays which are less than or equal to Sequential decoding.
A.5.3
Comparison of all TPC Modes
Mode
Eb/No at
BER = 10
-6
Eb/No at
BER = 10
-8
Spectral
Efficiency
Symbol Rate
Occupied *
Bandwidth for 1
Mbps Carrier
QPSK Rate 1/2 Viterbi
(see Note 1)
3.8 dB
7.2 dB
1.00 bits/Hz
1.0 x bit rate
1190 kHz
BPSK Rate 21/44 Turbo
2.8 dB
3.3 dB
0.48 bits/Hz
2.1 x bit rate
2493 kHz
BPSK Rate 5/16 Turbo
< 4.0
< 4.0 dB
0.31 bits/Hz
3.2 x bit rate
3808 kHz
{O}QPSK Rate 1/2 Turbo
3.0 dB
3.5 dB
1.00 bits/Hz
1.0 x bit rate
1190 kHz
{O}QPSK Rate 3/4 Turbo
3.9 dB
4.3 dB
1.50 bits/Hz
0.67 x bit rate
793 kHz
8-PSK Rate 2/3 TCM
and R-S (IESS-310)
(see Note 2)
6.1 dB
6.6 dB
1.82 bits/Hz
0.56 x bit rate
666 kHz
8-PSK Rate 3/4 Turbo
7.0 dB
8.0 dB
2.25 bits/Hz
0.44 x bit rate
529 kHz
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