3.2.4.12.2. RSC DB Decoder parameters

3.2.4.12.2.1. --dec-type, -D

Type:

text

Allowed values:

BCJR CHASE ML

Default:

BCJR

Examples:

--dec-type BCJR

Select the decoder algorithm.

Description of the allowed values:

Value	Description
BCJR	Select the BCJR DB decoder [Rsdb-BCJR74].
CHASE	See the common --dec-type, -D parameter.
ML	See the common --dec-type, -D parameter.

3.2.4.12.2.2. --dec-implem

Type:

text

Allowed values:

GENERIC DVB-RCS1 DVB-RCS2

Default:

DVB-RCS1

Examples:

--dec-implem DVB-RCS1

Select the implementation of the decoder algorithm.

Description of the allowed values:

Value	Description
GENERIC	Select a generic implementation that works on any trellis.
DVB-RCS1	Select an implementation dedicated to the DVB-RCS1 trellis (faster than the GENERIC implementation).
DVB-RCS2	Select an implementation dedicated to the DVB-RCS2 trellis (faster than the GENERIC implementation).

3.2.4.12.2.3. --dec-max

Type:

text

Allowed values:

MAXS MAXL MAX

Examples:

--dec-max MAX

Select the approximation of the \(\max^*\) operator used in the trellis decoding.

Description of the allowed values:

Value	Description
MAXS	\(\max^*(a,b) = \max(a,b) + \log(1 + \exp(-|a - b|))\).
MAXL	\(\max^*(a,b) \approx \max(a,b) + \max(0, 0.301 - (0.5 |a - b|))\).
MAX	\(\max^*(a,b) \approx \max(a,b)\).

MAXS for Max Star is the exact \(\max^*\) operator. MAXL for Max Linear is a linear approximation of the \(\max^*\) function. MAX for Max is the simplest \(\max^*\) approximation with only a \(\max\) function.

Note

The BCJR with the \(\max\) approximation is also called the max-log-MAP algorithm.

3.2.4.12.2.4. References

[Rsdb-BCJR74]

L. Bahl, J. Cocke, F. Jelinek, and J. Raviv. Optimal decoding of linear codes for minimizing symbol error rate (corresp.). IEEE Transactions on Information Theory (TIT), 20(2):284–287, March 1974. doi:10.1109/TIT.1974.1055186.