## 2 The ITU-R P.1546-6 Wave Propagation Model  
The internationally acknowledged and accepted wave propagation model, widely used for terrestrial services, including mobile telecommunications networks, is defined in \begin{table}
\begin{tabular}{l l l} \hline \hline
**Model Type** & **Advantages** & **Disadvantages** \\ \hline \multirow{3}{*}{**Empirical**} & Fast, efficient, widely used in & Limited to measurement-based \\  & planning; applicable in urban, rural, & environments; does not model \\  & and indoor environments; adaptable & physical effects like reflection or \\  & via optimization. & diffraction. \\ \hline \multirow{3}{*}{**Deterministic**} & High accuracy, considers & \\  & terrain/environment, & Computationally expensive; slow for \\  & frequency-independent; models & large-scale simulations; complexity \\  & propagation effects precisely. & increases with environment details. \\ \hline \multirow{3}{*}{**Hybrid**} & Combines empirical and deterministic & Requires data calibration; more \\  & benefits; balances efficiency and & complex than empirical models but \\  & accuracy; supports broad frequencies. & simpler than deterministic ones. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of wave propagation models. \begin{table}
\begin{tabular}{l c c} \hline \hline
**Model Type** & **3.6 GHz** & **6 GHz** \\ \hline
**Empirical** & ITU-R P.1546-6 [6] & SUI Model [11; 12] \\ \hline
**Deterministic** & Parabolic Equation Modeling [14] \\ \hline
**Hybrid** & ITU-R P.452-17 [18] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Classification of the wave propagation models considered in this article. ITU-R Recommendation P.1546-6: _Method for point-to-area predictions for terrestrial services in the frequency range 30 MHz to 4000 MHz_. This recommendation is maintained by the ITU-R WP 3K working group, responsible for point-to-area propagation in general [26]. This wave propagation model is purely empirical, based on a set of propagation curves based on the measured results [27], which are clustered at 100 MHz, 600 MHz, and 2000 MHz, taking into account several types of propagation paths (land, cold sea, and warm sea). In the example curve series shown in Figure 2, the field strength levels are plotted as a logarithmic function of distance for a given frequency, propagation path type, \(h_{1}\), and time percentage. The model is applicable in the frequency range from 30 MHz to 4000 MHz, requiring inter- and extrapolation between the 100 MHz, 600 MHz, and 2000 MHz curves. The maximum length of the propagation path is 1000 km. The type of propagation path can be terrestrial or sea, with a distinction being made between cold sea, warm sea, and general sea paths. The importance of the temperature distinction between sea types arises, for example, from the more frequent reporting of super-refraction in warm seas [28; 29], which may result in paths with lower path loss than in cold seas. In general, it can also be concluded that due to the homogeneity of the water surface, lower path loss can be assumed for wave propagation over large, contiguous water surfaces. In principle, \(h_{1}\) is the effective height of the transmitting antenna, which depends primarily on the type (land, sea, or mixed) and length of the propagation path. For land paths, (\(d\leq 3\) km) is the height of the antenna above ground level for short distances, and for longer paths, it is the height relative to the surrounding terrain. For sea paths, the physical height above sea level is applicable, but the model is only reliable for antennas higher than 3 m. For mixed paths, values must be determined separately for each section and then combined by interpolation. The time percentage is the percentage of the time that the real measured field strength level can exceed the calculated field strength level estimated by the model when looking at an average year [27].