Path Loss Prediction for Mobile Digital TV Propagation Under Viaduct

By the end of 2009, the service for in-vehicle mobile digital TV has been successively carried out in many cities around the world. Viaducts over roads are common in urban areas. In this paper, a 3-dimension six-ray tracing model reveals the fading law of UHF wave for in-vehicle digital TV system under the impact from viaducts, subject to transmitting antenna being higher than viaduct deck. The model takes into account the six rays that undergo line-of-sight (or viaduct transmission) propagation, ground reflection, as well as edge diffraction. In order to obtain more accurate knowledge of path loss law in an actual moving TV system, the 90th percentile of path loss values within the space 10 m have been analyzed. It has been illustrated that factors that influence path loss law include wave polarization, height of two antennas and the horizontal distance between transmitting antenna and viaduct deck axis. The path loss law predicted by the six-ray model shows a reasonable match with measurement results which have a great disparity in those estimated by the popular used propagation models.