Research On Single Carrier Fast Adapdive Equalization Used In Aero-Video Communication System

As an important part in information system, aero-video communication has become a heated research topic in recent years. Characteristics of channel in aero-video communication system are dynamic and fast multi-path fading. Equalizer used to cope with the channel fading is determinant for the performance of aero-video communication system. Adaptive equalization can catch up with time dynamic changes of channel and adjust its taps automatically, so it is a great choice to confront channel decline in aero-video communication system. The principle work of this dissertation is the research on single carrier fast adaptive equalization techniques based on channel characteristics in aero-video communication system.In this dissertation four parts about single carrier adaptive equalization and related techniques in aero-video communication are discussed. First, wireless channel and aero-video communication channel with their impact on signals are analyzed to help understanding the background of this dissertation. The channel model of aero-video communication system for simulation is introduced.Then different types of single carrier adaptive equalization are introduced. Adaptive equalization, one of the most used equalization techniques, can catch up with channel changes in real time, and automatically adjust the taps. Arithmetic rules such as peak distortion rule, least mean square rule, and recursive least square in wide use are introduced.Next, the structure, working principle and characteristics of adaptive DFE are analyzed. One particular kind of DFE called Partial DFE is introduced. Partial DFE can eliminate part of backward multi-path in advance and thus, lighten feedback filter’s burden. In order to speed up convergence rate of taps’coefficients, one approach is proposed to improve this structure. That is to use graduation restriction technique to update taps’coefficients or namely in the different working period of DFE, to use different length of steps to update taps’coefficients. Computer simulation results indicate that the proposed fast adaptive partial DFE inherits merits of original partial DFE and moreover speed up convergence rate and enhance SNR-BER performance of equalizer after applying the graduation restriction technique.Then adaptive iterative equalizer combined with phase track is studied. Phase noise and remaining carrier frequency error will hinder the convergence of equalizer taps’coefficients or even prevent equalizer from working in extremely bad channel conditions. Iterative equalization technique and overlapped DFE are introduced first. Then one kind of adaptive iterative overlapped equalizer is introduced which use the output of equalizer and error to estimate phase offset. However, since the estimation relies upon FFF, FBF and slicer, uncertain elements are quite many. In this dissertation a new method to estimate phase offset also combined with iterative overlapped equalizer is proposed. It uses output of slicer and input of equalizer to get phase offset. Verified by computer simulation, the improved algorithm proposed in this dissertation accelerates equalizer convergence rate and enhances SNR-BER performance.