Mocomtech CDM-QX - Manual (Page 172)

CDM-Qx/QxL Multi-Channel Satellite Modem with DoubleTalk™ Carrier-in-Carrier® Revision 7
Forward Error Correction Options MN/CDMQX.IOM
7–6
Table 6-5. Turbo Product Coding processing delay comparison
FEC Mode (64 kbps data rate) End-to-end delay, ms
Viterbi, Rate 1/2 12
Viterbi Rate 1/2 + Reed-Solomon 266
Turbo Product Coding, Rate 3/4 47
Turbo Product Coding, Rate 21/44, BPSK 64
Turbo Product Coding, Rate 5/16, BPSK 48
Turbo Product Coding, Rate 7/8 245 *
Turbo Product Coding, Rate 17/18 69
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 seen that the concatenated Reed-Solomon cases
increase the delay significantly (due mainly to interleaving/de-interleaving) while the TPC cases
yield delays, which are much less.
*
A larger block is used for the Rate 7/8 code, which increases decoding delay.
7.5.4 Comparison of all TPC Modes
Mode
Eb/No at
BER = 10
-6
Guaranteed
(Typical in
parentheses)
Eb/No at
BER = 10
-8
Guaranteed
(Typical in
parentheses)
Spectral
Efficiency
Symbol Rate
Occupied *
Bandwidth
for 1 Mbps
Carrier
QPSK Rate ½ Viterbi *
6.0 dB
(5.5 dB)
7.3 dB
(6.8 dB)
1.00 bits/Hz 1.0 x bit rate 1190 kHz
BPSK Rate 21/44 Turbo
2.9 dB
(2.6 dB)
3.3 dB
(3.0 dB)
0.48 bits/Hz 2.1 x bit rate 2493 kHz
BPSK Rate 5/16 Turbo
2.4 dB
(2.1 dB)
2.8 dB
(2.5 dB)
0.31 bits/Hz 3.2 x bit rate 3808 kHz
QPSK Rate ½ Turbo
2.9 dB
(2.6 dB)
3.2 dB
(2.8 dB)
0.96 bits/Hz 1.05 x bit rate 1246 kHz
QPSK Rate ¾ Turbo
3.8 dB
(3.3 dB)
4.4 dB
(4.0 dB)
1.50 bits/Hz 0.67 x bit rate 793 kHz
QPSK Rate 7/8 Turbo
4.3 dB
(4.0 dB)
4.5 dB
(4.2 dB)
1.75 bits/Hz 0.57 x bit rate 678 kHz
QPSK Rate 17/18 Turbo
6.4 dB
(6.0 dB)
6.9 dB
(6.5 dB)
1.90 bits/Hz 0.53 x bit rate 626 kHz
8-PSK Rate 2/3 TCM **
and R-S (IESS-310) 6.5 dB
(5.6 dB)
6.9 dB
(6.0 dB)
1.82 bits/Hz 0.56 x bit rate 666 kHz
8-PSK Rate ¾ Turbo
6.2 dB
(5.7 dB)
6.8 dB
(6.3 dB)
2.25 bits/Hz 0.44 x bit rate 529 kHz
8-PSK Rate 7/8 Turbo
7.3 dB
(6.8 dB)
7.5 dB
(7.1 dB)
2.62 bits/Hz 0.38 x bit rate 453 kHz
8-PSK Rate 17/18 Turbo
9.3 dB
(8.9 dB)
10.3dB
(9.9 dB)
2.85 bits/Hz 0.35 x bit rate 377 kHz
16-QAM Rate 3/4 Turbo
7.4 dB
(7.0 dB)
8.2 dB
(7.7 dB)
3.00 bits/Hz 0.33 x bit rate 396 kHz
16-QAM Rate 7/8 Turbo
8.1 dB
(7.7 dB)
8.3 dB
(7.9 dB)
3.50 bits/Hz 0.28 x bit rate 340 kHz
16-QAM Rate 3/4 **
Viterbi/Reed-Solomon 8.1 dB
(7.5 dB)
8.6 dB
(8.0 dB)
2.73 bits/Hz 0.37 x bit rate 435 kHz
16-QAM Rate 7/8 **
Viterbi/Reed-Solomon 9.5 dB
(9.0 dB)
10.1 dB
(9.5 dB)
3.18 bits/Hz 0.31 x bit rate 374 kHz