Comparison of GTD propagation model wide-band path loss simulation with measurements

Abstract

The geometrical theory of diffraction (GTD) wedge diffraction has been used successfully in the GTD propagation model to predict narrowband continuous-wave (CW) radiowave propagation characteristics. The GTD propagation model uses a two-dimensional terrain profile approximated as piecewise-linear and computes reflection and diffraction effects with model output representing a complex approximation to the narrowband channel transfer function. Using the narrowband GTD model as a starting point, a wideband terrain-sensitive model has been developed which is capable of predicting wide-bandwidth propagation characteristics. The complex wideband channel transfer function calculated by the GTD model is transformed to the time domain by a fast Fourier transform (FFT). The results are then used to predict time-domain radio transmission loss in the form of a bandlimited approximation to the channel impulse response. Important channel parameters such as delay spread, and wideband received signal level can then be calculated. The GTD predicted results are put in a suitable format and compared with measurements obtained by SRI International. >