CiM-550 IP Enabled Satellite Modem

Rev. 2

Forward Error Correction

CD/CIM550.IOM

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,

64

BPSK

 

Turbo Product Coding, Rate 5/16,

48

BPSK

 

 

 

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

Nothing!

improvement compared with every other FEC

 

method in use today

 

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

 

 

 

95