Research On Channel Modeling And Receiving Technology Of Massive MIMO In Multipath Environment In CRAHNs Network

In recent years,the available spectrum resources have become scarcer,and improving spectrum utilization efficiency and improving communication quality have become the focus of research.The CRAHNs(Cognitive Radio Ad Hoc Networks)network can improve spectrum utilization.However,when the wideband CRAHNs network is affected by multipath fading,its reliability is degraded.In severe cases,communication cannot be performed.The MIMO(Multiple Input Multiple Output)receiving technology can be effective.Fight multipath effects and reduce the effects of fading.Therefore,this paper studies the receiving technology of large-scale MIMO systems based on CRAHNs network multipath environment,including the establishment of channel model,channel estimation and channel compensation algorithm.(1)The channel model largely affects the communication performance of the system,so it is necessary to establish a channel model that can truly reflect the channel characteristics.This paper studies and analyzes the SCM series model,WINNER series model and 3D time evolution model,and compares the performance of several channel models.The results show that the 3D time evolution Massive MIMO channel model can better reflect the channel characteristics of massive MIMO.Therefore,this model is used as the model basis for the research of transmission technology in this paper.(2)The advantages of Massive MIMO receiving technology require accurate channel state information,and state information can be obtained by pilot-based channel estimation.However,with the increase of the number of antennas,the existing pilot-based channel estimation algorithms have problems such as high complexity or insufficient accuracy.Therefore,a channel estimation algorithm with low performance loss and low complexity is proposed,which is a low rank block channel estimation algorithm.The simulation results show that the proposed algorithm can reduce the channel estimation complexity to a large extent without reducing the system performance,so that massive MIMO can be applied to more practical scenarios.(3)An adaptive iterative channel estimation compensation algorithm is proposed for the problem that the pilot insertion interval affects the estimation accuracy of the system.The simulation shows that with the addition of the channel compensation algorithm,the system error rate always remains within 10-4 with the increase of the pilot interval,while the system performance without the compensation algorithm increases with the pilot interval,and the system performance gradually decreases.And when the insertion pilot interval is large,the system error rate performance is only slightly smaller than the system performance when the pilot interval is 1 by the channel estimation compensation algorithm.