Radio Wave Propagation Modeling In Tunnel Using The ADI-PE Method

With the development of the national economy and the improvement of the living standards, mobile users require increasingly high quality wireless network, hoping to use more stable mobile communication network when taking the subway, trains and other vehicles through the tunnel. When the mobile operators design the wireless network in tunnel, they need to eliminate signal bind area, optimize the position of base station to provide reliable wireless communication channel, the basic of the above work is to analyze the characteristics of the wave propagation. Thus, it is particularly important to study the wave propagation characteristics in tunnel.In this thesis, in order to optimize the wireless system such as GSM-R, the radio wave propagation in tunnel is modeled using the Alternative Direction Implicit Parabolic Equation (ADI-PE) method. The main innovation points of this thesis are as follows:1. This chapter focuses on a modified ADI-PE method, a new (MF)-ADI-PE which is fourth-order accuracy in the marching plane is presented for modeling the radio wave propagation in tunnel environment. The new approach maintains the same computational efficiency with the original ADI-PE method, while significantly improving the computational accuracy.2. We proposed a new channel model, which contains three propagation regions:near region, multi-mode region and far region, the FDTD method, PE method and modal analysis method are utilized in these three regions respectively. FDTD method can give detailed information with a high resolution in the near region, PE method compute the field rapidly in the multi-modes propagation region, and radio wave propagation can be modeled by fundamental modes in the far field region.3. We proposed a new pass loss model to calculate the pass loss in the near region and the far region by formula, which gives deep insight into the relationship between the parameters of antennas and characteristic of wave propagation. Also the location of break point and the position of transmitting antenna are discussed to give accurate prediction of channel model. The model provides the theoretical basis and reference for antenna design in the tunnels.4. Finally, the new channel model is verified by comparing with the experiment results taken in the Massif Central in south-central France.