Research On 3D Channel Reconstruction And Terminal Performance Test In MIMO OTA Setup

MIMO OTA is a multi-antenna performance test method,which simulates the target channel environment in a laboratory environment and puts the MIMO terminals into the environment to observe its throughput performance.With the development of MIMO technology in 5G,MIMO devices are becoming more and more widely used.So,mobile phone manufacturers,operators and communication associations are paying more and more attention to MIMO OTA.As one of the key technologies of 5G,3D MIMO introduces a 3D channel propagation environment for MIMO terminals,and also promotes terminal performance testing from 2D MIMO OTA to 3D MIMO OTA.Among the exiting three MIMO OTA test methods,the multi-probe anechoic chamber method has been widely praised by industry,academic and standard organizations such as 3 GPP and CTIA for accurately and reproducibly simulating the real channel environment.In this context,based on the channel reconstruction method,this paper studies how to accurately reconstruct the 3D channel environment in 3D MPAC and performs 3D MIMO OTA terminal performance test.The main research work has the following three aspects:1.Optimization of 3D uniform probe configuration.The influencing factors of channel reconstruction accuracy in 3D MPAC are determined by target channel model,test area sampling mode,test area target constraint function,probe configuration mode and probe power weight distribution algorithm.In this paper,the three-dimensional coordinate sampling method and the spherical surface sampling method are simulated and compared.The spherical surface sampling method which can ensure that the error inside the test area is below error of the spherical sampling points is selected as the sampling method of this paper.Then the target constraint functions of minimizing the maximum error and minimizing the total error are compared.Based on the simulation results,this paper selects the minimum error sum which can obtain a small average error as the target constraint function.On this basis,the pre-fading synthesis method is used to simulate the channel simulation accuracy under different 3D probe configuration schemes.Through the research results,the general rules of analyzing the optimal upper and lower ring pitch angle,the number of intermediate ring probes and the number of upper and lower ring probes are discussed,and a better 3D uniform probe configuration scheme is proposed,the RMS statistics of the spatial correlation error of the sampling points of this scheme are 68%lower than the traditional scheme.2.Design and implementation of 3D non-uniform probe combination optimization algorithm.The 3D non-uniform probe configuration considers the directionality of the channel model.Under the premise of ensuring the channel environment simulation accuracy,the probe with less contribution is closed,and the appropriate probe combination is selected to reduce the number of channels used by the channel emulator and further reducing the 3D MPAC system cost.Considering the effectiveness of genetic algorithm in function optimization and combination optimization,the genetic algorithm is applied to the probe combination selection problem.In the paper,the modules of initial group setting,feature parameter coding and hybrid variation iteration are designed and implemented.The simulation results show that the proposed algorithm outperforms the existing one-time selection method and step-by-step selection method in the accuracy of probe combination selection.3.3D MPAC MIMO OTA test platform setup and terminal performance test.Based on the above simulation results and MIMO OTA test principle,the 3D MPAC MIMO OTA test platform was built,and the system calibration was performed to ensure that the signal experienced the same fading from the base station to the test area.Performance testing of the MIMO terminal is performed based on the platform using the 2D channel model and the 3D channel model,respectively.The comparison of test results show that the 2D terminal throughput is between the ideal conduction condition and the better antenna configuration in 3 GPP TR 37.977standard,which is consistent with the reference data.At the same time,by comparing the terminal throughput of the 2D channel model and the 3D channel model,it is found that the 3D channel environment can bring better throughput performance to the terminal.