Comtech EF Data SDM-300A - Manual (Page 244)

SDM-300A Satellite Modem Revision 6
Forward Error Correction (Options) MN/SDM300A.IOM
9–8
Table 9-1. 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 that 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.
9.6.3 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)
6.0 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
QPSK / OQPSK Rate 1/2
Turbo
3.0 dB
3.5 dB
1.00 bits/Hz 1.0 x bit rate 1190 kHz
QPSK / OQPSK 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 RS (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