BCJR algorithm

The BCJR algorithm is an algorithm for decoding of defined on trellises (principally convolutional codes). The algorithm is named after its inventors: Bahl, Cocke, and Raviv. This algorithm is critical to modern iteratively-decoded error-correcting codes including turbo codes and low-density parity-check codes.

Contents

Steps involved

Based on the trellis:

  • Compute forward probabilities <math>alpha</math>
  • Compute backward probabilities <math>beta</math>
  • Compute smoothed probabilities based on other information (i.e. noise variance for , bit crossover probability for )

Variations

SBGT BCJR

Berrou, Glavieux and Thitimajshima simplification.

Log-Map BCJR

Max-Log-Map BCJR

Implementations

See Also on BitcoinWiki

External links

Source

http://wikipedia.org/