Propagation characteristics of UHF simulcast signals in tunnel environments

China uses the longwall method in coal mining. Coal is transported by trains along a system of tunnels. Reliable and flexible mobile communications are crucial to the operation of mining and the lives of miners. We first report the experimental results of using 900 MHz indoor digital cordless telephones to provide a mobile communication service in a coal mine haulageway tunnel. The results are so encouraging that serious research is being undertaken. Research shows that mining operation does not need high capacity mobile communications. So, the simulcast multiple excitation scheme based on digital cordless telephone technology is believed to provide mine tunnels with a new alternative mobile communication approach. The principles of the simulcast multiple excitation techniques are described. In order to characterize simulcast multiple excitation tunnel radio propagation channels, the paper develops the ray-tracing propagation model for the single excitation scheme and validates the model with experimental data. Finally, the model is extended to study the propagation characteristics of simulcast signals in tunnel environments