Simulation Program for Soft-Input Soft-Output Using Viterbi Algorithm

This article presents a simulation program employing the Viterbi algorithm for soft-input soft-output (SISO) processing. The program serves as a computational tool for modeling communication system behavior, specifically simulating modulation and demodulation techniques based on soft-input and soft-output principles. Through MATLAB/Simulink implementation, the program probabilistically processes continuous-valued inputs (soft-decisions) and generates reliability-weighted outputs using trellis-based path metric calculations. Key algorithmic features include: - Modified Viterbi decoder implementation with log-likelihood ratio (LLR) processing - Forward-backward recursion for soft-output generation - Branch metric computation accommodating analog input signals By utilizing this program, researchers can effectively analyze real-world application scenarios of SISO techniques, providing valuable insights for designing and optimizing communication systems. The simulation framework enables parametric studies investigating how various system parameters (e.g., signal-to-noise ratios, modulation schemes) impact performance metrics like bit error rate. This facilitates system performance enhancement and reliability improvement through iterative simulation-based optimization. The program holds significant application potential in telecommunications, serving as a valuable research tool for both academic and industrial practitioners in developing advanced communication systems. Code implementation includes configurable parameters for channel models, modulation types, and decoding depth to support flexible experimentation.