Spatial Characteristics of Wireless Channel in Tunnel with Imperfect Walls

Abstract

The successful design and application of the physical layer techniques of the wireless network, including MIMO, adaptive OFDM, and mining antenna, to name a few, need the detailed knowledge of the spatial characteristics of the transmitted signals. This paper provides a modal approach to quantify the spatial distribution of the waves in tunnels in detail. We develop the modal theory for propagation in a tunnel with imperfect walls, which are lossy, rough, and tilted. And then, we discuss the transmission power of the antenna as a function of the angles of departure (AOD). On this basis, we take the half-wave dipole antenna as an example to analyse by simulations. The theoretical results show that the angular power distribution in the rectangular tunnel follows Gaussian distribution. The angle spread (AS) of the waves can be influenced by the tunnel walls. The roughness of the wall surface is most important in small tunnels and at low frequencies, whereas the wall tilt is most important in large tunnels and at high frequencies.