Research On Blind Estimation And Blind Equalization Of Wireless Channels

In the process of wireless communication,due to the complex characteristics such as random time variation,multipath and high background noise,the signals received in the system may cause severe inter symbol interference,affecting the normal transmission of the signal.Channel estimation and equalization techniques are the most effective means to reduce inter-symbol interference(ISI)in communications.Traditional research mostly focuses on adaptive channel estimation techniques which uses pilot symbols or training sequences,but the training sequence occupies a large amount of bandwidth,which causes loss of system capacity.This problem affects the quality of the next generation of communication.In the upcoming commercial 5G communication system,if this problem can be solved,it is bound to effectively increase the information transmission rate.This paper presents the problem of channel estimation and equalization in underwater acoustic communication and 5G communication.The corresponding blind equalization and blind estimation algorithm are proposed.In this underwater acoustic communication application scenario,this paper introduces the multi-input single-output system model and uses the model to estimate the channel.Considering that the ocean noise presents a strong impact,this paper uses the decision circle method to reduce the influence of ocean noise on the channel blind estimation algorithm.And the cost function of the equalization algorithm is rewritten.A new blind equalization algorithm is proposed.Finally,the simulation proves that the proposed algorithm can significantly shorten the iteration speed and ensure the stability of the algorithm.In the 5G communication scenario,Sparse Code Division Multiple Access(SCMA)is an air interface access technology proposed for 5G communication.Due to factors such as multipath effect and noise,the inter-symbol interference is especially serious in wireless communication.In this paper,blind equalization technology is combined with sparse code division multiple access technology.SCMA can transmit multiple users simultaneously on the same resource block,which causes the traditional equalization can not to be used in SCMA,because the same resource block is equipped with user information through different channels,so it can not be equalized at the signal receiving end.In this paper,the equalization algorithm is moved to the signal transmitting end,which successfully solve the above problems.The theoretical and simulation results show that applying the blind equalization technique to sparse code division multiple access can reduce the system bit error rate and improve the system spectrum utilization.