Geometry-Based Channel Model for Extra-Large Scale Array Communication Systems

The dimension of extra-large scale array (XL-array) is very large, and the spatial non-stationarity along the large-scale array is present, i.e., the users/scatterers only "see" a portion of the XL-array, which is called visibility region (VR). Also, the users/scatterers are located in near-field region of XL-array, which results in a failure of conventional uniform plane wave (UPW) assumption. Considering the spatial non-stationarity, a geometry-based channel model using VR and non-uniform spherical wave (NUSW) assumption, which is used to describe the phase and amplitude variations across the array elements, is proposed for XL-array communication systems in this letter. Based on the proposed XL-array model, the near-field spatial correlation, which depends on the phase and amplitude across array elements, is derived, and the conventional far-field spatial correlation is a special case of the proposed near-field spatial correlation, which is validated by using numerical result. Based on the derived spatial correlation, the average received signal power is also investigated in this letter. Also, the numerical results show that the VR obviously affects the performance gain of XL-array communication systems.