3.2.4.10.2. RSCDB Decoder parameters¶

3.2.4.10.2.1. --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 .

CHASE

See the common --dec-type, -D parameter.

ML

See the common --dec-type, -D parameter.

3.2.4.10.2.2. --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).

3.2.4.10.2.3. --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.

3.2.4.10.2.4. 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.