The turbo principle in joint source channel decoding of variable length codes

The turbo principle has been widely applied to various detection/decoding problems in recent years. Here we show how the general idea can be extended to a communication scheme where a variable length code is used for data compression followed by a channel code to protect the data against channel errors. Iterations are performed between the channel decoder and the decoder for the variable length source code. Since the exchange of extrinsic information is essential for the performance of turbo decoding schemes we describe how EXIT-charts can be applied to predict the performance of the iterative source-channel decoding approach.