Mod/Demod Processing Delay; Comparison Of All Tpc Modes; Table 7-2. Turbo Product Coding Processing Delay Comparison - Comtech EF Data SNM-1001L Installation And Operation Manual

SNM-1001L Satellite Modem
Forward Error Correction Options
7.3.2

Mod/Demod 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 7-2 shows, the processing delays for the major FEC types, including the three TPC modes:
Viterbi, Rate 1/2
Sequential, Rate 1/2
Viterbi Rate 1/2 with Reed Solomon
Sequential Rate 1/2 with Reed Solomon
Turbo Product Coding, Rate 3/4, Offset QPSK
Turbo Product Coding, Rate 21/44, BPSK
Turbo Product Coding, Rate 5/16, BPSK
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 clearly seen that the concatenated Reed-
Solomon cases increase the delay very significantly (due mainly to interleaving/de-interleaving),
while the TPC cases yield delays which are less than or equal to Sequential decoding.
7.3.3

Comparison of all TPC Modes

Table 7-2. Turbo Product Coding Processing Delay Comparison

FEC Mode (64 kbps data rate) Mod/Demod delay, ms
7–3
Revision 1
MN/SNM1001L.IOM
12
74
266
522
79
64
48