Coding Analysis Of Turbo Codes And Their Application In Improved Turbo Coding Schemes

Turbo code, an error correcting codes with near Shannon limit performance, are regarded as milestone in the history of channel coding theory. The ideas of designing channel coding in terms of increasing the minimum Hamming weight are changed into reducing the multiplicities of the low weight codewords. Due to the presence of interleaver, it is difficult to accurately calculate the distance spectrum of Turbo codes like traditional Convolutional Codes. Nowadays the research of Turbo codes are emerged, however, the analysis of the accurate distance spectrum of Turbo codes is not sufficient.In retrospect to channel coding theory and Turbo coding structure, the common algorithms for Turbo distance spectrum searching are reviewed at first. Based on the constrained subcode algorithm, the most efficient algorithm for the accurate Turbo distance spectrum determination, a more efficient algorithm combined with impulse response analysis method is proposed in this thesis to estimate the minimum Hamming weight of the constituent encoder with interleaved input orders. Futhermore, several improved algorithms corresponding to impulse response analysis method are proposed to speed up the computation as well. In addition, the distance spectrum of Turbo code is employed in the improved Turbo coding schemes in order to achieve a better bit error rate performance.The work in this thesis provides helpful exploration on further study and improvement of Turbo codeword weight spectrum determination algorithm. The results in this thesis offer useful reference for high quality Turbo coding and decoding techniques.