Turbo Codes In Wireless Communications And Turbo Equalization Technique

With the rapid development of communication technology and the increasing demands of users, the next generation of wireless communications needs to provide the multimedia data service abundantly. This requires higher spectral efficiency and better quality of service (Qos) of the communication system. In order to fulfil these requirements many proposals have been put forward including the application of Turbo codes in 3GPP standard. Another new technology–MIMO can increase the data transmission rate and improve the date transmission quality while maintaining bandwidth.The presence of multipath effect of the wireless mobile channel, which causes channel distortion and intersymbol interference, is a serious problem and equalization technology is widely applied. Turbo equalizer combines equalization with decoding, significantly improving the performance of the former system.This thesis focuses on Turbo encoding and decoding technology and their application to equalization and Turbo equalization applied in frequency-selective MIMO channels. The main content of this thesis includes:1. The dynamic characteristics in broadband wireless fading channels are analyzed in detail, and the system transmission model is given. The common adaptive equalization technologies are discussed and the equalizers are classified. The basic equalization theories and principles are deducted. The performance simulation of the typical equalization algorithms is given.2. The basic principles and structures of Turbo codes (PCCC and SCCC included), are discussed and studied. Then the effect of different parameters on the performance of turbo codes is analyzed. The parameters include different decoding algorithms, iteration number, interleave length, generator polynomial of component codes, code rates and so on. Some simulation experiments on Turbo codes with the Log-Map decoding algorithm in AWGN channel are done.3. Basic principles and structures of Turbo equalization are analyzed. The basic algorithm for Turbo equalization is studied. Then contrast analyses of algorithms are also made through simulation. A Turbo equalization based on MMSE criteria is discussed in detail, and the effect of iteration number on equalization in the classical Proakis channel is also analyzed. Simulation results demonstrate that Turbo equalization based on MMSE criteria can improve the performance of BER significantly.4. Turbo equalization applied in frequency-selective MIMO channels is studied. At first MIMO channel models are analyzed. Then a space-time Turbo equalization applied in frequency-selective MIMO channels is studied in detail. At last simulation experiments are made to testify the effectiveness and feasibility of this algorithm.