Research On Turbo Coded Modulation Technique

Turbo coded modulation technique,which combines the high power efficiency of Turbo codes with high bandwidth efficiency of coded modulation technique,can suit the demand of high efficiency and reliability in wireless communications and possess wide application foreground.Based on the research of Turbo codes and coded modulation technique,two typical kinds of Turbo coded modulation,called BITCM and T-TCM,are thoroughly researched.For BITCM,the basic coding and decoding structure,the simplification of its bit metric calculation,the sensitivity to the estimate precision of SNR,the bit assignment rule and the combination with constellation shaping technique are investigated.An improved bit metric scheme is proposed to overcome the shortage of the existing scheme. Simulation result shows that the scheme proposed in this thesis can achieve performance very close to the optimal bit metric calculate algorithm with less calculation complexity.For T-TCM,the symbol-based MAP decoding algorithm and special iterative decoding process are analysed.Then the performance comparison with BITCM and the application of sliding window MAP algorithm in T-TCM scheme are researched.The adaptive Turbo coded modulation is also discussed. A simplified adaptive Turbo coded modulation scheme is proposed and its parameters,like power efficiency,stoppage probability and bandwidth efficiency,are analysed. Simulation result shows that,comparing to the unchangeable Turbo coded modulation scheme,adaptive Turbo coded modulation technique can get better compromise between communication quality and bandwidth efficiency.