Comtech EF Data SNM-1001L - Manual (Page 180)

SNM-1001L Satellite Modem Revision 1
Forward Error Correction Options MN/SNM1001L.IOM
7–4
Note: For additional data, refer to Appendix A, for BER specifications.
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 * 6.0 dB 7.2 dB 1.00 bps/Hz 1.0 x bit rate 1190 kHz
BPSK Rate 21/44 Turbo 3.0 dB 3.3 dB 0.48 bps/Hz 2.1 x bit rate 2493 kHz
BPSK Rate 5/16 Turbo < 4.0 dB < 4.0 dB 0.31 bps/Hz 3.2 x bit rate 3808 kHz
Offset QPSK Rate 1/2 Turbo 3.0 dB 3.5 dB 1.00 bps/Hz 1.0 x bit rate 1190 kHz
Offset QPSK Rate 3/4 Turbo 3.9 dB 4.3 dB 1.50 bps/Hz 0.67 x bit rate 793 kHz
8-PSK Rate 2/3 TCM **
and RS (IESS-310)
6.1 dB 6.6 dB 1.82 bps/Hz 0.56 x bit rate 666 kHz
8-PSK Rate 3/4 Turbo 7.0 dB 8.0 dB 2.25 bps/Hz 0.44 x bit rate 529 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 SNM-1001L transmit
filtering.
**
Included for comparative purposes.
It can be seen that the 8-PSK Rate 3/4 Turbo performance closely approaches that of the Rate
2/3 TCM/Reed-Solomon case – the BER performance is within approximately 0.4 dB. However,
it should be noted that the Rate 3/4 Turbo mode is 20% more bandwidth efficient than the TCM
case. The additional advantages of Turbo (lower delay, performance during fades etc) should
also be considered.
7.4 Uncoded Operation (No FEC)