Ridge feature extraction and effect on radio propagation for wireless communications

Abstract

When diffraction of ridges is required for predicting radio signal in mountainous regions, the realistic shape of ridges is often simplified (e.g., as a knife edge or a wedge). Also, the ridge orientation is usually ignored and the EM waves are assumed to be normally incident on the ridge. As more accurate radio propagation prediction is needed for advanced wireless communications, it is necessary to take into account more realistic features of ridges. For example, the slopes and orientation of ridges should be considered as two key features since they directly affect the values of diffraction coefficients. In this paper we present methods to extract these features of ridges based on digital terrain elevation data. The effect of the ridge orientation on the diffracted field is then investigated.

Diffraction from multiple ridges: Comparing three-and two-dimensional results

“…Only when the ridges are all horizontal and parallel one another, the 2D and 3D ray paths are identical. In [1], we have shown that the path loss calculated using 3D ridges may be more than 5 dB different than that using 2D height profiles.…”

“…(2) Larger difference between the azimuthal angles ( ) of the two ridges results in larger path loss differences between 2D and 3D for soft polarizations; but for hard polarizations, the trend is opposite, except for one case when = 40° and = 55°. (3) The maximum path loss difference is about 10 dB which is twice the difference for a single ridge as discussed in [1]. …”

“…In [1], algorithms are developed to extract ridge structures from digital terrain elevation databases. It is shown that the 3D features of a single ridge may cause more than 5 dB difference for the received signal power compared with the result calculated based on the 2D height profile.…”

Ray Tracing for Radio Propagation Modeling: Principles and Applications

“…As more and more digital elevation data are available with better resolutions, it is getting more convenient to extract terrain features important for radio propagation modeling such as the mountain peaks and ridges. In [105], a simple method is used to extract 3D ridges from digital elevation data. The extracted ridges then serve as diffraction wedges in simulating the radio wave propagation.…”