Research And Implementation Of Non-stationary Stochastic Models For Air-to-ground Channels

In recent years,as an important part of the intelligent transportation system in the Fifth Generation of Mobile Networks(5G),Air-to-Ground(A2G)communication has drawn great attraction from academia and industry.In order to design and evaluate the performance of A2G communication systems,the research and implementation of non-stationary stochastic models for A2G channels is of great significance.The A2G channels are complex and changeable,and it is difficult to describe the non-stationary characteristics with a stationary stochastic process.The Markov non-stationary channel model can well simulate the non-stationary characteristics of signal fading envelope of the real A2G channels on the time axis.The theoretical research of the channel model needs the support of engineering practice.It is necessary to discuss the realization method of Markov non-stationary channel model and improve the efficiency of simulation calculation.Massive Multiple-Input Multiple-Output(MIMO),as a MIMO enhancement technology,has broad application prospects in A2G communication scenarios as it has many attractive advantages,such as high spectral efficiency and significantly increased energy efficiency.As the massive MIMO channels present some new characteristics,it is very important to establish an accurate and efficient massive MIMO model for A2G channels.In this thesis,we study non-stationary stochastic models for A2G channels.The main research work and innovations are summarized as follows.1)To solve the problems of large storage space and low computational efficiency in the A2G channel model simulation,an optimized storage scheme is proposed.A large number of stream processors in the Graphics Processing Unit(GPU)are used to realize the the parallel calculation of Markov non-stationary channel model simulation based on the look-up table method.And thus,we improve computing efficiency from both storage space optimization and parallel computing.2)With geometry-based stochastic modeling method,a three-dimensional single-hop cylindrical model for massive MIMO A2G channels is established.The model deploys a two-dimensional Uniform Planar Array(UPA)on the ground station,and introduces vectors to describe the geometric relationship between the transceiver antennas and the scatterer clusters,making the model more universal.3)When modeling the spatial non-stationary characteristics of the channels,in view of the problem that the classic birth-death process is difficult to migrate to higher-dimensional antenna arrays,a novel scatterer cluster evolution mechanism is proposed,namely the scatterer update process.It also solves the problems of non-random variation in the number of scatterer clusters and high spatial correlation in other spatial non-stationary characteristic modeling methods.The simulation results show that the proposed scatterer update process can effectively simulate the spatial non-stationary characteristics of the two-dimensional antenna array.