Premier Mounts CDM-600 specifications End-to-End Processing Delay

CDM-600 Satellite Modem	Revision 7
Forward Error Correction Options	MN/CDM600.IOM

This new LDPC/TPC codec module may be installed in any existing CDM-600, as a simple field upgrade, or already installed in new modems ordered from the factory. It requires Firmware Version 1.6.0 (or higher) to be installed.

Please contact the Sales Department at Comtech EF Data for pricing and delivery information.

The table that follows compares all TPC and LDPC modes available in Comtech EF Data’s CDM-600, and shows Eb/No 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)

7.7.3 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, the processing delays for the major FEC types, including the three TPC modes:

Table 7-6. 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	47
Turbo Product Coding, Rate 21/44, BPSK	64
Turbo Product Coding, Rate 5/16, BPSK	48
Turbo Product Coding, Rate 7/8, O/QPSK	245 *
Turbo Product Coding, Rate 0.95, O/QPSK	69
LDPC Coding, Rate 1/2	248
LDPC Coding, Rate 2/3, O/QPSK	296
LDPC Coding, Rate 2/3, 8-PSK, 8-QAM	350
LDPC Coding, Rate 3/4, O/QPSK	321
LDPC Coding, Rate 3/4, 8-PSK, 8-QAM, 16-QAM	395

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 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 less than or equal to Sequential decoding.

*A larger block is used for the Rate 7/8 code, which increases decoding delay.

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