Turbo Equalization In Wireless Mobile Communication System

Turbo codes proposed by C.Berrou el. at. in ICC'93 are a class of powerful channel codes. Their iterative decoder works like a turbo engine so that it is named after Turbo codes. Turbo code attracts the significant coverage of researchers in information theory, since Turbo codes can achieve remarkable error performance at low signal-to-noise rate close to the Shannon capacity limit. Turbo codes consist of two component convolutional codes concatenated by an interleaver. The difference between Turbo codes and traditional channel codes is that Turbo codes almost realize random coding by the interleaver and increase the effective block length greatly. Furthermore Turbo codes use iterative decoding strategy, which exchanges the information between two component decoders in iterations and approach asymptotically the performance of max likelihood decoding. In academic fields, Turbo codes not only are a class of performed-well error correct codes but also provide a way to theory limits. So the principle of Turbo codes and its application become a research hotspot. This thesis focuses on the application of Turbo principle on equalization, i.e., Turbo equalization. The main work includes:1. We discuss the basic scheme and principle of Turbo equalization. Because inter-symbol interference (ISI) in communication is similar to convolutional encoding, the concatenation of a convolutional code, an interleaver and ISI channel is similar to a serial concatenated convolutional code. So at the receiver we can equalize and decode jointly using iterative method as decoding a serial concatenated convolutional code. That is Turbo equalization. We set up the simulation flat, research the bit error ratio (BER) performance of Turbo equalization based on the maximum a-posteriori probability (MAP) equalizer and linear minimum mean-squared error (LMMSE) equalizer respectively and give the simulation results.2. Depending on the well understanding of the Turbo equalization, we propose three modified Turbo equalization scheme: the Turbo equalization based on precoding, based on Turbo codes and based on parallel equalization scheme. The purpose of the first two modified scheme is to further improve the BER performance of Turbo equalization, while the last modified scheme is used to mitigate the equalization...