Design Of Joint Coding-channel Equalization Scheme For Double Selective Fading Channels

With the rapid development of wireless communication technology,there are many new applications,such as communication on the Internet of cars and high-speed trains.In addition,in the classical application scenario represented by shortwave communication,with the continuous development of relevant technologies in recent years,shortwave communication is gradually supporting diversified broadband communication services including video and voice.The above communication scenarios are characterized by high mobility and high transmission bandwidth.In practical communication,the relative motion of high mobility or reflection media will lead to the problems of Doppler frequency skew and channel timevarying,and the high bandwidth transmission will be affected by channel multipath effect.Multipath propagation causes frequency selective fading.Doppler extension makes the channel appear time selective fading.This kind of channel is called double selective fading channel which presents frequency selective fading and time selective fading simultaneously and double selective fading will bring serious challenge to the reliability and transmission efficiency of communication system.Therefore,based on the traditional channel equalization algorithm,this paper studies the channel equalization algorithm and optimization scheme for double selective fading channel.The main research work of this paper is as follows:A joint iteration algorithm of channel equalization and decoding based on Orthogonal Approximate Message Passing(OAMP)is proposed for Single-Input-Multiple-Output communication system model.Firstly,using the gaussian information of the received signal to realize the information interaction within the equalization module,and using the Gaussian message passing principle to ensure the information independence and Gaussian,OAMP equalization algorithm is realized.Then,on the basis of OAMP equalization algorithm,the results of channel decoding module are fed back to the equalization module for utilization,and the joint iterative algorithm of channel equalization and decoding based on OAMP is realized.Experimental results show that under the same channel environment and the same channel estimation algorithm,the equalization and decoding accuracy of the proposed scheme are better than the traditional algorithms,and the multipath effect and fast fading effect of the double selective fading channel can be well reduced.Aiming at the Single-Input-Multiple-Output communication system model,a multi-antenna diversity receiving scheme for double selective fading channel is designed to make full use of diversity gain provided by multi-antenna and improve detection accuracy of receiver.Based on OAMP equalization algorithm,two multi-antenna diversity receiving schemes for double selective fading channels are designed for multi-antenna systems.Firstly,the likelihood ratio information calculated by OAMP equalization algorithm is combined to realize the distributed equalization-merger scheme.Then,the received signals of each antenna branch and the channel estimation matrix are combined to transform the SingleInput-Multiple-Output system into a Single-Input-Single-Output system to realize the centralized merger-equalization scheme.Finally,a large number of comparative experiments are designed using simulation data and measured sky wave data respectively.The experimental results show that the performance of the two diversity receiving schemes is similar to that of the single antenna system,and the performance of the two diversity receiving schemes is significantly improved.