Research On Image Enhancement Method In Pulsed Eddy Current Thermal Imaging Technology

As a key technology in mobile communication systems,precoding technology will also play an important role in future the fifth generation(5G)communication systems.Compared with linear precoding,non-linear precoding has better performance.However,most researches are performed under ideal conditions assuming that the transmitter has known perfect Channel State Information(CSI),and few researches mention how is nonlinear precoding performance in realistic systems where the transmitter CSI is imperfect and the channel estimation has errors.In order to better apply nonlinear precoding to realistic systems,this thesis explores the performance of non-linear precoding in realistic situations,analyzes the effect of imperfect csi and channel estimation error on nonlinear precoding and proposes a novel non-linear precoding scheme.Firstly,this thesis briefly introduces the system model of Multiple input and multiple output(MIMO),and analyze the difference and connection between single user multiple input multiple output(SU-MIMO)and multiple user multiple input multiple output(MUMIMO).In addition,this thesis introduces some typical linear precoding technologies and the simulation verification and performance analysis are also presented.Secondly,this thesis gives thorough research about two typical non-linear precoding techniques,Tomlinson-Harashima precoding(THP)and vector perturbation(VP)precoding,and both of which have been simulated and evaluated under various condition.Besides,some existing improved algorithms of non-linear precoding have been presented.Then,this thesis designs and implements a 5G downlink simulation platform,which adopts a modular design and is highly flexible and highly scalable.After introducing the simulation flow of the platform,this thesis analyzes the functions of each module and then focuses on the encoding and decoding of low density parity check code(LDPC),soft demodulation technology,precoding technology,the structure of demodulation reference signal(DMRS)in 5G,channel estimation,and the conventional equalizers,etc.Finally,the performance of non-linear precoding in realistic systems is investigated on the above simulation platform and the non-ideal factors affecting non-linear precoding performance are analyzed.Then,in view of the problems of non-linear precoding in realistic systems,this thesis proposes a VP precoding scheme using a novel equalizer.Simulation results verify that the proposed scheme can achieve a remarkable performance gain than the conventional VP precoding.