基于传播图理论的隧道场景无线信道模型构建与验证

Construction and Verification of Wireless Channel Model in Tunnel Scenario Based on Propagation Graph Theory

针对非视距NLOS(Non Line of Sight)隧道环境的特殊性,基于传播图理论提出通过细化散射点间传递函数的方法提高隧道信道建模精度。构建隧道几何模型,并将模型划分为多个散射点集合,电磁波的传播路线可表述为点集合的排列,通过相邻点集合间子传递函数的级联可得到该路线的传递函数。引入点集合间转移概率的概念描述其可视情况,用传播路线上相邻点集合间转移概率之积调整该路线的传递函数。所有路线传递函数之和即为信道频域传递函数,进而得到信道冲激相应CIR(Channel Impulse Response),并与相同环境下实际信道测量结果进行对比。在此基础上分析多天线相关性、角度分布与信道容量,发现隧道中密集的反射会导致天线间相关性较高及信道矩阵退化。

Aiming at the particularity of non line of sight （NLOS） scenarios, a new method was proposed to improve channel modeling accuracy by refining the transfer function among scattering points based on propagation-graph channel theory. First, a tunnel geometry model was constructed, which was divided into multiple scattering point sets. The propagation route of the electromagnetic wave can be expressed as a permutation of point sets. The transfer function of the route can be acquired by cascading the sub-transfer function of two adjacent point sets. The mutual visual degree of two sets was described by the concept of transfer probability between the point sets, and the transfer function of the route was adjusted by the product of transfer probability between two adjacent point sets. Based on the whole channel transfer function obtained through the sum of all routes＇ transfer functions in frequency domain, the channel impulse response （CIR） in time domain was obtained. Based on the comparison made between the simulation results and actual measurement results, and the analysis on multiple antenna correlation, angle distribution as well as channel capacity, it was found that inten-sive reflection in confined tunnel would lead to higher correlation coefficient among antennas and degradation of channel matrix.