Mocomtech CIM-550 - Manual (Page 121)

CiM-550 IP Enabled Satellite Modem Rev. 2
Forward Error Correction CD/CIM550.IOM
95
FEC Mode (64 kbps data rate) End-to-end delay, ms
Viterbi, Rate 1/2 12
Sequential, Rate 1/2 74
Turbo Product Coding, Rate 3/4, QPSK 79
Turbo Product Coding, Rate 21/44,
BPSK 64
Turbo Product Coding, Rate 5/16,
BPSK 48
Note: 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.
FOR AGAINST
Exceptionally good BER performance - significant
improvement compared with every other FEC
method in use today Nothing!
No pronounced threshold effect - fails gracefully
Exceptional bandwidth efficiency for Rate 3/4 QPSK
- 40% less than Viterbi and concatenated Reed-
Solomon
Coding gain independent of data rate (in this
implementation)
Low decoding delay
Easy field upgrade in CiM-550