Radio Propagation Models For Wireless Communication In Rail Transit

With the development of wireless communication and rail transit, CBTC (Communication BasedTrain Control) system has become a major part of communication system in rail transit, which is easyto be set up and consumes less investment. But it requires higher reliability and stability. While,wireless signal is so fragile to the environment that leads to unexpected attenuation. Hence, the studyof radio propagation behavior securing the reliable wireless environment for CBTC system is asignificant task.The topic was originated from the project of wireless communication system in rail transitaiming at guiding its deployment and handoff processes. Firstly, it overviewed the radio propagationmodels and summarizes their characteristics. Secondly, it introduced the environment andcommunication system in rail transit. This thesis proposed the DHHB (Distance, Relative Humidityand Height Based) path-loss model using multiple linear regression method based on the oldpropagation model theory and on-site test results. Also it proposed the multipath propagation modelfor rail transit environment utilizing ray-tracing and radio propagation behavior theories, whichcombined the two-ray model and multi-ray model. And compared to the DHHB path-loss model, theresult showed that proposed models can fit the on-site test data better than old models and match oneanother. In the end, calculated the mid-value curve for the guidance of the deployment and handoffprocesses, including the selection of antenna height and distance of AP (Access Point) as well as thehandoff threshold. It was tested by AtkkPing and Ixchariot using icmp and udp protocols. The resultsshowed that wireless communication system ran well in rail transit environment with the tips offeringby the proposed models.