Source-Dependent Channel Coding and its Application to CELP

Efforts to minimize the effect of channel errors on low-rate speech coders, such as code-excited linear prediction (CELP), can be divided into methods which change the robustness of the source coder [1], and procedures which add error correction and error detection by means of a separate channel coder. The channel coder often provides several levels of protection, with more error protection being assigned to the parameters or bits which are judged to be more sensitive to channel errors [2–4]. Such protection can be considered to be a form of source-dependent channel coding. This paper focuses on improving source-dependent channel codes through optimization of objective error criteria.