A Study Of Mixed-Field Holographic Communication Method Based On Reconfigurable Intelligent Surface

With the commercial deployment of the 5th Generation Mobile Communication(5G)wireless networks and the exploration and development of applications in vertical industries,the development of the 6th Generation Mobile Communication(6G)wireless networks has attracted widespread attention.Reconfigurable Intelligent Surface(RIS)is a new revolution in the manipulation of electromagnetic waves or local control of wave amplitude and phase at an unprecedented level by altering spatially and temporally varying electromagnetic properties,enabling specific manipulation of electromagnetic waves such as reflection,refraction,absorption focusing and steering.Its high performance,low cost and low energy consumption are considered to be one of the critical enabling technologies for building smart radio environments in future 6G wireless networks.However,due to its structural characteristics,RIS itself lacks the ability to actively process signals,which leads to a cumbersome channel estimation process in the wireless communication systems it assists.Furthermore,with the rapid increase in communication frequency bands and the gradual expansion of antenna apertures,the near-field and even more complex applications of large-scale RIS are coming to the fore.This is due to the qualitative difference in transmission between the different radiated fields of the antenna,which will inevitably result in a large performance loss if the traditional channel model is still used.Based on this,this paper proposes a holographic beam assignment method for large-scale RIS,and constructs a mixed near-and far-field channel model for users in complex scenarios aided by large-scale RIS.The details of the research are as follows:1.To address the current situation in which the channel estimation process in RIS-assisted communication systems is cumbersome and difficult,a holographic communication method based on the wave interference principle is proposed.Starting from the nature of interference fringes,it is reasoned and reduced through the perspective of power analysis,and finally an RIS-based holographic beam assignment algorithm is provided.In addition,an engineering-applicable Hall Reconfigurable Intelligent Surface is provided,providing theoretical and engineering support for the deployment of holographic RIS applications.2.To address the background of the lack of accurate channel models applicable to mixed near-field and far-field beam reception users in research of RIS,a mixed channel model based on existing far-field and near-field channel models is proposed.Simulation results show that the proposed mixed channel model can bring better gain and robustness to the system than the single channel model.3.To address the lack of proper configuration of the proposed hybrid channel model for the weight parameters in different scenarios,a mixed Orthogonal Matching Pursuit(OMP)beam estimation algorithm based on the existing near-field and far-field compressed sensing beams is proposed.In the simulation scenario setup,the proposed hybrid OMP algorithm has a 2.1d B gain improvement over the far-field OMP algorithm and a 1.3d B gain improvement over the near-field P-OMP algorithm.The proposed algorithm has a 3d B improvement over the far-field OMP algorithm and a 1.4d B gain over the near-field P-OMP algorithm after optimal configuration of the weighting parameters.