Comtech EF Data CIM-300L - Manual (Page 128)

CiM-300L IP Enabled Satellite Modem Rev. 1
FEC & Turbo CD/CIM300L.IOM
102
6.3.3 C
OMPARISON OF ALL
TPC M
ODES
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
{O}QPSK Rate 1/2 Turbo 3.0 dB 3.5 dB 1.00 bps/Hz 1.0 x bit rate 1190 kHz
{O}QPSK Rate 3/4 Turbo 3.9 dB 4.3 dB 1.50 bps/Hz 0.67 x bit rate 793 kHz
8PSK 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
8PSK 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
CiM-300L transmit filtering.
**
Included for comparative purposes.
It can be seen that the 8PSK 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.