Wireless Communication Systems, Adaptive Equalization Techniques

In the field of wireless communications,because of multipath effect,the finity of channel bandwidth and incomplete channel,inter-symbol interference(ISI) is inescapability during the data transfer.Equalizers are often used to combat the influence of channels for improving communication's quality and decreasing ISI in receivers.Due to high rate transmitted data and fast time-varying real channel,the equalizers must be able to track the changes of channel parameters adaptively and modify weights value ceaselessly,consequently,can achieve the objective of removing ISI.To find adaptive equalization algorithms which have fast convergence speed,low compute complexity and good numerical value stability have important theoretic and realistic significance.In this thesis,the adaptive equalization algorithms are mainly discussed.Firstly we introduce the background and meaning of the problem,expatiate MIMO and adaptive equalization technology and develop status.Then the dynamic idiosyncrasy of the mobile wireless channel,the MIMO channel building model significance, classification and the MIMO multipath decaying channel model are given.And the adaptive equalization principle,classify and corresponding structural are analyzed also.The LMS,RLS,CMA,MCMA and DD-LMS are researched,simulated and compared in detail.Finally this paper studied a mixed algorithm:a modified constant modulus cost function in which a leaking gene was brought,then combined DD-LMS is applied.This algorithm has a fast convergence rate and a lower residual error when converged recovers the channel phase error automatically while equalizing.Computer simulation validates that the algorithm of this algorithm is effective.The contrast of simulation result shows its validity.