Prediction of Shadowing Effect of Tall Buildings on Digital Terrestrial Television using the Knife-Edge Diffraction Model

Abstract

Digital Terrestrial Television (DTTV) is the means of broadcasting digital TV signals through line-of-sight. Losses due to shadowing caused by tall structures along the propagation path can be efficiently formulated using the theory of single or double knife-edge diffraction. However, the technique does not take care of cases with multiple edges without overestimating the losses necessitating the need for a more accurate method. Therefore, this work developed an improved algorithm for the prediction of shadowing effect of tall buildings on digital terrestrial television reception using the knife-edge diffraction model for multiple edges. The direct paths between transmitters and receivers were defined and their profiles were extracted using the Google Earth software. The Japanese knife-edge diffraction method was modified and used to compute the diffraction loss. The total path loss was estimated by summing diffraction loss and the free space loss. The power received at each location was measured and compared with the theoretical values of the ITU-R, Japanese knife-edge and modified Japanese knife-edge models. The developed algorithm performed better in terms of path loss and received power when compared with conventional methods. This work will assist in estimating link budgets and footprints of DTTV transmitters for effective coverage.