ISCA Archive - Combined source-channel coding for a very noisy channed (original) (raw)

Combined source-channel coding for a very noisy channed

Alain J. Vigier

This paper reports the study of codecs at global bit rates (source and channel coding) of 8, 12 and 16 kb/s. We examine combined source-channel coding algorithms for very noisy channels. We first describe our application: transmission over VHF channel, using frequency hopping (FH). We hypothesize an hostile environment, therefore the bit error rate can reach a non-uniform rate of 25%! Next, we describe the 3 speech coders used in this study and analyse their sensitivity to bit errors. Efficient channel coding and error recovery procedures are proposed, such as using some matrix (cascaded) codes and repeating or smoothing parameters assumed in error. These combined source-channel coding procedures yield to much better results than if both coding procedures were carried out separately or if we used a speech coder at the total transmission rate.