MATLAB Implementation of BCJR Decoding Algorithm

This MATLAB implementation provides complete source code for the BCJR decoding algorithm with extensive explanatory comments. The code structure demonstrates key algorithm components including: forward probability calculations using alpha recursion, backward probability computations via beta recursion, branch metric evaluations, and log-likelihood ratio (LLR) derivations. Implementation details cover trellis structure initialization, probability normalization techniques, and efficient memory management for handling state metrics. The code includes practical examples and explanatory sections that illustrate the algorithm's working principles through step-by-step probability propagation across trellis stages. This implementation serves as an educational resource for understanding MAP algorithm mechanics, featuring modular design that separates core functions for forward-backward passes and LLR computation. The commented code highlights important considerations for numerical stability and efficient computation in soft-input soft-output (SISO) decoding applications.