中文摘要：

隧道环境与陆地上移动通信有显著不同,需要对其无线信道特性进行研究.本文提出了一种改进的射线跟踪法,能够对隧道环境无线信道特性高效地仿真,降低了射线跟踪的计算复杂度,同时采用一种新的坐标系描述弯道的几何形状,便于对弯道部分进行射线跟踪.本文将路径损耗的仿真结果与北京地铁14号线的实测结果进行对比,对比表明：改进的射线跟踪法能够有效地预测路径损耗;直道中K因子在-8~25 d B范围内变化,且随着距离增大有减小的趋势.

英文摘要：

Since the radio environment in tunnels is significantly different from that for land mobile communications,it is critically important to investigate the radio channel characteristics in tunnels. In this paper,an enhanced ray-tracing algorithm is proposed,which can simulate the radio channel characteristics in tunnels efficiently with reduced computational complexity. In addition,a new method is employed to describe the curved tunnels,which makes it easier for ray-tracing in curved tunnels. The simulated path loss is compared against the measured path loss in Beijing Subway Line 14,which shows that our proposed algorithm can be used for effective path loss prediction in tunnels. The range of simulated K factor is- 8 ~25 d B,and it decreases with the distance between transmitter and receiver.