Novel Hybrid Propagation Model inside Tunnels

The propagation situations inside tunnels vary with the distance between transmitter and receiver, as well as the relative size of the users. This paper presents a novel hybrid propagation model covering three propagation mechanisms with two types of users. In the first case, the users are relatively small in size compared with the tunnel. The entire process is interpreted by combining the free space propagation model and the limited multi-mode propagation model. In the second case, for relatively large users , the free space propagation can be replaced by the near shadowing effect to some extent or totally. Hence, the whole procedure is described by coupling the statistical model in the near shadowing zone, the free space model, and the limited multi-mode model. Two groups of measurements are employed to validate the model. The results show good agreement and, therefore, the model supports an effective way to predict the propagation situation inside tunnels for different types of users.