Evaluation des entrelaceurs au sein des Codes Turbo par simulations

摘要

This thesis evaluates the performances of Turbo Codes. These are among the best error correcting codes for digital communications. They are concatenated codes composed of two recursive and systematic convolutionnal codes. An interleaver is used to allow the two encoders to see different sequences of bits.;The decoding process is what gives to those codes the property of turbo. This process is iterative and is done with two decoders in serie. The extrinsec information links the two decoders and offers some reliability information for the second decoder. This allows the second decoder to correct errors the first one may have not modified. The MAP algorithm is used and allows the Turbo Codes to reach excellent performances.;Many factors have to be considered to analyze the performances of Turbo Codes. The parameters of the two convolutionnal encoders are among them. We may also consider the decoding algorithm.;Nevertheless, the interleavers are the sub-systems considered in this thesis. The pseudo-random interleavers are first studied. The pure random interleaver is evaluated and gives very good performances. We then introduce the symmetric interleaver, to which we add the property of randomness. (Abstract shortened by UMI.).