3D Stochastic Geometry Channel Model of Cell-Free Massive MIMO System

Cell-free massive multi-input multi-output (MIMO) system performs many new characteristics compared with the traditional centralized massive MIMO system. In this paper, a three-dimensional (3D) non-stationary cell-free massive MIMO channel model based on stochastic geometry is proposed, which combines the double-loop model and semi-ellipsoidal model to comprehensively consider the distribution of static and moving scatters in the environment. By introducing the birth and death process and the scatter visible region division model, the time-variant propagation path is analyzed. Combined with the line-of-sight (LoS) path and non-line-of-sight (NLoS) path component, the channel impulse response and space-time correlation function are derived. Statistical characteristics of the channel are analyzed, such as time autocorrelation function (ACF), space cross-correlation function (CCF), and stationary interval. Finally, the effects of parameters such as the limited number and the speed of scatters on the channel characteristics are analyzed by simulation.