Abstract
Attenuation caused by tree shadowing is an important factor for describing the propagation channel of satellite services. Thus, vegetation effects should be determined by experimental studies or empirical formula- tions. In this study, tree types in the Black Sea Region of Turkey are classified based on their geometrical shapes into four groups such as conic, ellipsoid, spherical and hemispherical. The variations of the vegetation depth according to different tree shapes are calculated with ray tracing method. It is shown that different geometrical shapes have different vegetation depths even if they have same foliage volume for different elevation angles. The proposed method is validated with the related literature in terms of average single tree attenuation. On the other hand, in order to decrease system requirements (speed, memory usage etc.) of ray tracing method, an artificial neural network is proposed as an alternative. A graphical user interface is created for the above processes in MATLAB environment named vegetation depth estimation tool (VdET).
Highlights
In the communication area, signal attenuation is a major problem and many researches have been aimed to model in different links such as land mobile satellite communications, terrestrial mobile communication (GSM, 3G, 4G etc.) and high altitude platforms (HAPs)
We focus on single tree vegetation depth based on four different tree types such as conic, ellipsoid, spherical and hemispherical
For every geometrical shape trees, vegetation depths (d) are calculated with the parameters used at training stage which are given in (1–4)
Summary
Signal attenuation is a major problem and many researches have been aimed to model in different links such as land mobile satellite communications, terrestrial mobile communication (GSM, 3G, 4G etc.) and high altitude platforms (HAPs). Average attenuation of trees was measured for land mobile satellites at UHF and L band by Vogel and Goldhirsh [1]–[3], Butterworth [4], [5], Ulaby et al [6], and Cavdar [7]. In [12], single tree attenuation was examined with the help of measurements at 1–4 GHz frequency band for 45 o elevation angle. The frequency dependence of vegetation effects for satellite links was studied in [13] and some attenuation measurements were performed at L-, S- and C-bands taking into consideration elevation angles between 25o and 90o [14]. For different terrestrial scenarios and different frequency bands, ITU-R Recommendation [16] includes vegetation attenuation models not valid for high elevation scenarios. In [17], models and measurements for land mobile satellite system were published
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