三维空间中近距离多天线信道的容量分析

针对多天线系统在近距离和远距离2种场景下信道矩阵的差异，基于球面波模型进行信道容量分析，并通过使用球面波模型（spherical wave model，SWM），研究了三维空间中近距离多天线直线传播（line of sight，LOS）信道容量。相比现有基于信道测试和计算机仿真的研究方法，在三维空间中建模任意方向的线性天线阵列，给出球面波模型下的近距离LOS信道矩阵，在此基础上推导了近距离LOS信道容量的闭式解。通过信道容量的闭式解和计算机仿真分析了影响近距离LOS信道容量的参数，揭示了近距离LOS信道容量的本质特征。理论和分析结果表明，在三发三收近距离LOS信道中，信道容量是“类余弦”的函数，即具有类似余弦函数的周期振荡特性，其变化特征由波长、阵元间隔、收发通信距离和阵列方向完全决定，通过合理设计这些参数使近距离 LOS 信道容量达到最大。

Analysis of the capacity for short-range multi-antenna channels in 3D space

Short-range multi-antenna line-of-sight (LOS) scenarios occurs more frequently than long-range multi-antenna LOS cases. However, plane-wave model is not suitable for short-range LOS cases. Unlike previous study based on channel sounding and simulation, we investigate the capacity for short-range multi-antenna LOS channels with the spherical-wave model (SWM) in three-dimensional (3D) space to obtain its close-form. The antenna array with arbitrary orientations in 3D space is modeled, and the channel matrix with the SWM is then derived. Based on this obtained channel matrix, the exact closed-form expression for the channel capacity is derived without channel state information (CSI) at the transmitter.By using the closed-form expression for the capacity and computational results, we analyze the factors governing the capacity behavior, and give the essential characteristics of the capacity for short-range LOS channels with the SWM. Both the analytical and computational results show that the capacity for short-range LOS channels with three transmitting and three receiving antennas reflects the cosine behavior, and the capacity is determined by the wavelength, the inter-element spacings, the transceiver distance and the orientations of the arrays. And the capacity can be maximized by specifically designing these parameters.