A parametric model for wireless propagation channels in tunnels

Wireless communication channels in large tunnels at microwave frequencies involve an interaction among many guided wave modes. It has been reported that spatial records of field strength versus axial distance in straight tunnels can be divided into two zones. Close to the transmitting source (near zone), the field consists of many modes interacting in such it way as to produce rapid decay and strong local variations. For greater distances (far zone), the field appears dominated by only a few principal modes, or a single mode, with less rapid decay and smoother variations. We form a parametric model that includes these characteristics in the two regions.