The last ten years have seen the appearance of a new type of correction code : the turbo codes. This represents a significant development in the field of error-correcting codes. The principle of decoding is to be found in an iterative exchange of information between elementary decoders, called extrinsic information, and it is this principle from which the term turbo originates. The turbo concept is now applied to block codes as well as other parts of a digital transmission system such as detection, demodulation and equalization. This book is concerned with three leading areas of information : the construction of concatenated codes and their properties, the problems of decoding, and the extension of turbo codes to other aplications. Applications that integrate turbo codes into their standards are mobile communications, interactive television, wireless networks and local radio loops. Future applications could include cable transmission, short-distance communication or data storage.