中文摘要：

目前的城市轨道交通车地通信技术大多采用2.4 GHz的ISM频段.本文给出2.4 GHz无线局域网在北京地铁昌平线隧道内传播的现场测试结果,并结合Fresnel区的定义以及Wireless InSite仿真软件研究隧道中2.4 GHz无线电波的传输规律,说明在实际隧道中使用经验混合传播模型计算近区和远区转折点的不足,以及隧道内金属反射体和其他遮挡物对转折点的位置确定存在较大的影响.利用最小二乘法对测试结果进行直线拟合,得到近区和远区不同的路径损耗因子,使近区信号波动相对于远区较剧烈的结论得到验证.对近区和远区的信号波动分布进行统计,指出其近似莱斯分布的特性.

英文摘要：

Technologies of wireless LAN working at the 2.4 GHz ISM frequency band are adopted in most train- wayside communication systems in CBTC in urban rail transit. In this paper, field test results of 2.4 GHz WLAN propagation in tunnels of the Beijing Subway Changping Line were given. Combining with the Fresnel Zone theory and Wireless InSite Simulation, the propagation characteristics of 2.4 GHz WLAN in subway tun- nels were studied. The disadvantages of the empirical hybrid model in calculating near field and far field break poins of real tunnels were illustrated and the existence of metal reflectors and other blocking shelters in tunnels is pointed out to have radical impact on positioning of break points. With the least square linear fitting of field test results, the mean path loss exponents of the near field and far field were worked out respectively, thus verifying the fact that signals in the near field fluctuated more severely than in the far field. Finally, statistics of small-scale fading distributions in the near field and far field were collected, which were verified to be ap- proximate to Rice distribution.