Research On Blind Channel Estimation For MIMO System

With the advent of 5G communication,the modern communication environment has become more complex,and short burst communication has become a communication method with strong anti-interference ability in modern communication systems.In the field of military communications,in order to complete the identification of non-cooperative communication signals,it is necessary to study the blind channel estimation problem.In the above communication scenario,new requirements on channel estimation in MIMO systems are needed to correctly recover the transmitted signal at the receiver.The number of received signal samples required for channel estimation need to be as few as possible,and the number of training sequence or pilots should be as small as possible,and even the receiver may not have the information of the training sequence or pilot.In this thesis,the blind channel estimation problem of MIMO system is studied in the above two scenarios.The main work are summarized as follows: 1.A blind channel estimation method based on transform matrix is proposed.The performance of the algorithm is analyzed theoretically.It is proved that the algorithm can solve the blind channel estimation problem when the number of transmitting and receiving antennas is small.The performance of the algorithm is simulated by software.It is proved that the algorithm can estimate the channel state information of the system without using training sequences or pilots.The algorithm proposed in this thesis has the performance close to the traditional scheme under the ideal channel state information,and the performance is obviously better than the traditional scheme when the channel state information is not ideal.In contrast,this thesis also introduces a traditional blind channel estimation method based on subspace method.The simulation experiment is carried out by software.It proves that the traditional method requires more received signal samples and more convergence speed,so that it could not be used for short burst communication and signal identification scenarios.2.The ambiguity problem inherent in the blind channel estimation method is analyzed theoretically.Based on the blind channel estimation method proposed in this thesis,an ambiguity elimination method based on source characteristics is proposed.Aiming at the communication scenarios such as signal identification that the signal transmission process can't be interfered,the inherent characteristics of pictures,audio and other sources could be utilized.This method can eliminate the ambiguity generated by blind channel estimation when training sequence and pilot information is unknown.3.Aiming at cooperative communication scenarios that the transmission scheme can be controlled such as short burst communication,an ambiguity elimination method based on short training sequence is proposed.This method can eliminate the ambiguity generated by blind channel estimation by using little training sequence information.By comparing the performance of the system before and after the ambiguity is eliminated,it is proved that the method can eliminate the symbol ambiguity and antenna order ambiguity of the source signal while sacrificing little spectral efficiency.