See the following references for detailed descriptions of the shown optimization

• T. Richardson and R. Urbanke, Modern Coding Theory, Cambridge University Press, New York, 2008
• L. Schmalen, Modern Error Correction - Lecture Nodes, University of Stuttgart, 2015
• F. Schreckenbach, Iterative Decoding of Bit-Interleaved Coded Modulation, PhD Thesis, Technical University Munich, 2007