Research On 5G Channel Propagation Characteristics And Fading Prediction Technology

With the rapid spread of mobile intelligent terminals and explosive growth of new-type applications,the fifth-generation(5G)and beyond 5G(B5G)com-munication systems with the requirement of large-bandwidth,low-latency and high-reliability have become an important research.Compared with the fourth-generation(4G)communication system,Three-Dimensional Multiple Input Multiple Output(3D MIMO)technology improves the spectrum efficiency with the increase of the elevation domain.In order to support the simulation and verification of key technologies in 5G and B5G systems,there is a strong need to research on the 3D MIMO channel propagation characteristics.Limited by the measurement equipment,test scenarios and quantitative results of the present research are few and still lacking.This dissertation utilizes the established 3D MIMO channel measurement system to research on the channel propagation characteristics intensively and proposes one kind of channel fading prediction technology for the present mainstream MIMO-Orthogonal Frequency Division Multiplexing(MIMO-OFDM)system.This dissertation includes the following aspects:(1)Multidimensional channel parameter estimation.In order to obtain the multi-dimensional channel parameters from the Channel Impulse Response(CIR)in the real channel measurement,it is essential to select an appropri-ate algorithm to estimate CIR.This dissertation expands the traditional Space Alternating Generalized Expectation Maximization(SAGE)algorithm to the frequency domain and 3D space domain.Moreover,in order to estimate the parameters in the time-varying channel,this dissertation introduces the Bayesian Estimation Kalman Filter(BEKF)algorithm and extends it to track the contin-uously evolving parameters with limited resolution in the real communication system.(2)3D MIMO channel space-domain angular parameter modeling and simulation method.This dissertation analyses the 3D MIMO channel angular parameters based on the power angle spectrum(PAS)and angular spread(AS)value for 3 typical scenarios.The scenarios consist of Outdoor-to-Indoor(O2I),Urban-micro(UMi),Urban-macro(UMa)and each includes 2 measurement locations.It shows that with the user(US)moving,the channel presents the spatial consistency property in terms of the azimuth angle of departure,azimuth angle of arrival,elevation angle of departure,elevation angle of arrival.AS values are compared in all scenarios.It is observed that the O2I scenario has the richest scatting environment in the elevation domain,which leads to the largest elevation AS values.In contrast,due to the large distance between the base station(BS)and US in the UMa scenario,the elevation domain has very little impact compared with the azimuth domain,which leads to the smallest AS values.Furtherly,based on the symmetry property of PAS distribution,we propose a random angular offset method for intra-cluster multi-path sampling in the channel simulation model.The proposed method makes the sampling results better to match the spatial and temporal correlations of the target PAS distributions with limited complexity,which is promising to be adopted in the future massive MIMO or high-speed channel simulation models.(3)The analysis on 3D MIMO channel system performance.This dissertation analyses the system performance of 3 typical scenarios in terms of single-user(SU)MIMO and multiple-user(MU)MIMO channel capacity,channel correlation and the capacity gap between 2D MIMO and 3D MIMO channels.In the case of 20dB SNR,when the BS and US are configured with 32 and 2 antenna elements respectively,a capacity increase of 82%,77%and 73%can be observed from SU to MU 3D MIMO in the O2I,UMi and UMa scenarios.It shows that higher multiplexing gain can be realized with more users in the 3D MIMO system.Moreover,compared with 2D MIMO,the eigenvalues of 3D MIMO channel correlation are distributed more uniformly and 3D MIMO can support the communication of more users.Therefore,more degrees of freedom are provided by the elevation domain in the case of 3D MIMO,which can support the transmission of more information.(4)The research on the fast time-varying MIMO channel fading pre-diction technology in the high-speed scenario.Based on the 3D MIMO channel propagation characteristics,the dissertation utilizes the channel spatial consistency property to propose a novel channel fading prediction framework in the high-speed scenario.With the full consideration of MIMO channel spatial characteristics,this framework combines the BEKF channel parameter track-ing algorithm and the proposed Cluster Drifting Based Prediction algorithm with the assumption of ’Cluster Drifing’.Therefore,the channel fading can be predicted with the tracking and fitting of the time-varying channel parameters.Compared with the traditional channel fading prediction method,the system Bit Error Rate(BER)obtained by CDBP method decreases significantly.