Soft-output-decoding: Some aspects from information theory

Recent literature presents methods for the analysis of concatenated coding schemes by solely characterizing the behavior of the component codes [4], [12], [16], [9], [7]. Component codes are analyzed either analytically using unique properties of special component codes, e.g., single-parity-check code or accumulator, or via simulations. The goals of this paper are to find fundamental insights into concatenated codes by analyzing the input-output relation of their components from an information-theoretic point of view. We derive the Information Processing Characteristic (IPC), which completely characterizes the behavior of a coding scheme comprising encoder, code and decoder for the general class of linear codes. For time invariant convolutional codes it is studied how the IPC can be obtained in practice