On Performance Of Large-scale Multi-antenna Wireless Channel Based On Channel Measurement

The fifth generation mobile communication system(5G)has drawn considerable attention from international researchers in recent years.Large-scale multi-antenna technology which deploys tens to hundreds.of antennas at base station(BS),as one of the key technologies for 5G,is believed to significantly improve capacity performance,spectral effi-ciency,and simplify transmission schemes.However,the practical reali-zation of these performance gains in real channel environments still needs to be verified through actual measurement.Therefore,for the deployment of large-scale multi-antenna technology in 5G systems,field channel measurements play an important role considering the propagation char-acteristics of wireless channels which vary with different scenarios and different frequency bands.This paper presents a large-scale multi-antenna channel measurement at the carrier frequency of 3.5 GHz and a band-width of 200 MHz in urban macro-cell(UMa)and outdoor-to-indoor(021)scenarios.The performances of multi-user capacity and channel correlation in real environment are analyzed.The main work includes:(1)Multi-user performance of large-scale multi-antenna channel for UMa scenario.In this scenario,two types of propagation conditions considering Line-of-Sight(LoS)and Non Line-of-Sight(NLoS)are se-lected.Based on the two-user measured channel data,the two-user and one-user channel capacity under different numbers of antennas at the transmitter(Tx)side is analyzed,and the comparison to i.i.d.channel performance is also performed.The results show that the performance of two-user measured channel capacity improves as the number of antennas increases,however,the capacity growth slows down as the number grows on.Moreover,when the number of antennas reaches 256,the two-user measured channel capacity at high SNR can reach 75%and 90%of the i.i.d.channel performance for LoS and NLoS propagation conditions,re-spectively.Then,the distribution of normalized channel eigenvalues and channel correlation characteristics are analyzed,and the results match with the capacity performance.When the number of antennas equipped at each user's side is increased from 2 to 16,the two-user channel capacity is significantly improved,but the factors such as antenna configuration at both the transmitter and receiver sides and scenario conditions may have impacts on the performance gain,and larger capacity gaps between two-user and one-user channel are obtained with large-scale mul-ti-antenna deployed at the Tx side.(2)Multi-user performance of large-scale multi-antenna channel for 021 scenario.In this scenario,the BS is distributed outdoor,and two users are deployed on two different floors with the same interior structure.Channel measurements are performed and two-user measured channel impulse responses are analyzed and studied for all the same aspects as in the last scene.The study shows that,the best performance is achieved when both users are located on the lower floor which has more outdoor scatterers in the environment,such as trees,etc.The capacity ratio to i.i.d.channel increases to 90%as the number of antennas grows up to 256.In addition,the two-user capacity under different shapes of two-dimensional large-scale multi-antenna array is analyzed,which provides a reference for the application of large-scale multi-antenna array in real environment.Overall,the two-user large-scale multi-antenna channel measure-ment platform at the center frequency of 3.5 GHz is set up in this paper.Based on the field measurements for UMa and 021 as two typical mobile communication scenarios,the measured large-scale multi-antenna chan-nel performance including the two-user capacity and channel correlation are analyzed and researched.