Comtech EF Data CDM-600/600L - Manual (Page 128)

CDM-600/600L Open Network Satellite Modem Revision 3
Forward Error Correction Options MN/CDM600L.IOM
6–8
It is clear that, in order to provide the best possible performance over the range of code rates from
1/2 to 0.95, both an LDPC and a TPC codec need to be offered.
In order to meet this requirement, Comtech EF Data has developed a combination LDPC/TPC
Codec module that can be added to the CDM-600/600L Modem, and which provides the operating
modes shown in Table 6-5:
Table 6-5. Available TPC and LDPC Modes
Operating
Mode
Rate Data Rate Range Comments
TPC Code
Rate/
Modulation Rate 21/44 BPSK 4.8 kbps to 3.2 Mbps To 4.772 Mbps with High Rate Turbo card
Rate 5/16 BPSK 4.8 kbps to 2.048 Mbps To 3.12 Mbps with High Rate Turbo card
Rate 1/2 QPSK, OQPSK 4.8 kbps to 9.54 Mbps High Rate Turbo card only
Rate 3/4 QPSK, OQPSK 7.2 kbps to 5.0 Mbps To 15 Mbps with High Rate Turbo card
Rate 3/4 8-PSK 10.8 kbps to 5.0 Mbps
To 20 Mbps with High Rate Turbo card
Rate 3/4 16-QAM 14.4 kbps to 5.0 Mbps
Rate 7/8 QPSK, OQPSK 8.4 kbps to 17.5 Mbps
High Rate Turbo card only
Rate 7/8 8-PSK 12.6 kbps to 20 Mbps
Rate 7/8 16-QAM 16.8 kbps to 20 Mbps
Rate 0.95 QPSK, OQPSK 9.1 kbps to 18.888 Mbps
Rate 0.95 8-PSK 13.6 kbps to 20 Mbps
LDPC Code
Rate/
Modulation) Rate 1/2 BPSK 4.8 kbps to 5.0 Mbps
TPC/LDPC Codec card only
Rate 1/2 QPSK, OQPSK 4.8 kbps to 10.0 Mbps
Rate 2/3 QPSK, OQPSK 6.4 kbps to 13.3 Mbps
Rate 2/3 8-PSK , 8-QAM 9.6 kbps to 19.0 Mbps
Rate 3/4 QPSK, OQPSK 7.2 kbps to 15.0 Mbps
Rate 3/4 8-PSK , 8-QAM 10.8 kbps to 20.0 Mbps
Rate 3/4 16-QAM 14.4 kbps to 20.0 Mbps
This new LDPC/TPC codec module may be installed in any existing CDM-600/600L, as a simple
field upgrade, or already installed in new modems ordered from the factory. It requires Firmware
Version 1.3.0 or higher to be installed in the CDM-600L; Firmware Version 1.6.0 or higher is
required in the CDM-600.
Please contact the Sales Department at Comtech EF Data for pricing and delivery information.
Table 6-7 compares all TPC and LDPC modes available in Comtech EF Data’s CDM-600/600L,
and shows E
b
/N
o
performance and spectral efficiency (occupied bandwidth) for each case. This
information will be of particular interest to satellite operators wishing to simultaneously balance
transponder power and bandwidth. The large number of modes offered will permit, in the
majority of cases, significant power and/or bandwidth savings when compared with existing
schemes such as concatenated Viterbi/Reed-Solomon, or the popular 8-PSK/Trellis/Reed-
Solomon (Intelsat IESS-310).
6.7.3 End-to-End Processing Delay
In many cases, FEC methods that provide increased coding gain do so at the expense of
increased processing delay. However, with TPC, this increase in delay is very modest. Table 7-6
shows, for the CDM-600/600L, the processing delays for the major FEC types, including the
three TPC modes: