Blind Equalization And Blind Identification Of Linear Time-Varying Fading Channel

In wireless digital transmissions, due to the delay dispersion of the transmitted symbols and the limitation of channel bandwidth, the channel may induce inter-symbol interference (ISI), which results the frequency selective fading. The relative motion between the base station and the mobile results in random frequency modulation due to different Doppler shifts on each of the multi-path components, also called time selective fading. A time-varying disperse channel is a channel that contain both frequency selective fading and time selective fading. In order to achieve fast and reliable communication, we need to identify and equalize the channel for the purpose of combating the effects caused by channel fading.hi this thesis, the characters of the linear fading channel are lucubrated. Some effective equalization techniques towards different channel fading are proposed. The following algorithms have been proposed and tested in the thesis:1 Frequency selective fading: Combine the isomorphism between the input spaceand the output space and propose a new approach to blind equalization of the channel. Compared with conventional methods, the new approach offers lower computational complexity, better performance, and more robust against the over-determination of the system order;2 Time Selective fading: A new approach to the equalization of time selectivechannel based on the zero-forced equalizer is proposed which is more simple in its structure of algorithm;3 Time-Varying channel: Using the instantaneous mean value changes of theoutput signal to extract the information of channel variations and model it using AR model, Kalman filter is then employed to track channel variations, it bears faster ability in tracking the variation of TV channels; Based on the isomorphism between the inputs and the outputs and some of the approaches using in MIMO system, a new algorithm of equalization of SIMO time-varying channel is proposed, which also share the merits of being robust against theover-determination of the system order; Model the time-varying channel using the multi-resolution decomposition wavelets, and then a blind identification method based 'on the model is proposed; At last, a new model for equalization and identification of MIMO system is proposed.Using some approach of blind equalization and together with the research on the time-varying channels to handle some of the problems shows its significance in both theory and practice. It is really a promising research topic. After been extended to CDMA system in order to eliminate MAI and ISI, it would by all means improve the efficient of mobile communications, and ensure the high effectiveness and reliability for 3G communication system.