# Radio Channel Modelling for VHF System Operating in the Offshore Wind Farms Propagation Environment
## 3 Results and Discussion
### Simulations for Systems Operating in the VHF Band in the Marine Environment of Wind Farms
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & & & & **Coherence Bandwidth for the** & **Coherence Bandwidth for the** & **Coherence Bandwidth for the** & **Selected Tower Radius for a** & **Selected Tower Radius for a** \\
**ID** & **Distance of the** & **Distance** & **Receiver from the** & **between** & **5 \(\times\) 5 Turbine Configuration** & **10 \(\times\) 10 Turbine Configuration** \\
**the Wind Farm** & **the Wind Farm** & **Wind Farm** & **Transmitter** & **[kHz]** & **[kHz]** \\
**(see Figure 10)** & **(see Figure 10)** & **and Receiver** & **Tower Radius** & **Tower Radius** & **Tower Radius** \\ \cline{3-6}  & & & & **3 m** & **4 m** & **3 m** & **4 m** \\ \hline
1 & 500 m (P1) & 2 Nm (P3) & 1.7 Nm & 262.733 & 227.648 & 178.468 & 155.227 \\
2 & 500 m (P1) & 10 Nm (P5) & 10 Nm & 73.748 & 63.947 & 134.112 & 116.221 \\
3 & 2 Nm (P2) & 2 Nm (P3) & 2 Nm & 224.176 & 194.19 & 211.424 & 183.201 \\
4 & 2 Nm (P2) & 10 Nm (P6) & 8 Nm & 123.083 & 106.633 & 134.112 & 116.221 \\
5 & 10 Nm (P4) & 10 Nm (P6) & 10 Nm & 102.816 & 89.057 & 102.751 & 89.009 \\
6 & 2 Nm (P2) & 2 Nm (P7) & 500 m & 1282.658 & 1110.82 & 1084.674 & 939.366 \\ \hline \hline \end{tabular}
\end{table} 
Table 14: Coherence bandwidth depending on the radius of the tower and the configuration of wind turbine spacing. Figure 11: Antenna radiation pattern modeled using ITU-R BT.1893-1 Annex 1 (**a**) and Annex 2 (**b**) for 160 MHz. Remarks: H 3 dB/10 dB—3 dB/10 dB beam width of the antenna in the horizontal plane; V 3 dB/10 dB—3 dB/10 dB beam width of the antenna in the vertical plane; FB—Front-to-back ratio; Tilt—represents the typical wind turbine relation to the vertical axis. bandwidth in difficult conditions (e.g., 25 kHz). When the VDES system is launched in Poland, it will be necessary to take into account the presence of the constructed wind farms. The simulation results presented in Figures 12 and 13 below show the reference communication system Carrier to Interference Ratio (CIR) plots for different wind farm spacing configurations (25 turbines--5 \(\times\) 5, and 100 turbines--10 \(\times\) 10), two turbine tower radius dimensions (3 m and 4 m) and different distance of the ship from the wind farm (500 m, 2 Nm, 10 Nm). The impact of the wind turbine dimension (tower radius) on the ship's reference communication system is most noticeable for small distances. The higher tower radius dimensions translates into the higher reflected power level according to ITU-R BT.1893-1 Annex 2 model [11], resulting in the higher interferences around the turbines, as can be seen in Figure 12 (\(b\) vs. \(a\), and \(d\) vs. \(c\)). The number of reflecting turbines also has a significant impact on the communication system CIR levels--the higher number of turbines the higher cumulative interfering areas, as can be seen in Figure 12 (\(c\) vs. \(a\), and \(d\) vs. \(b\)). Figure 12: CIR plots for reference communication system transmitting from the ship at a distance of 500 m from the wind farm, for different wind farm configurations and turbine tower radius: (**a**) 25 turbines (5 \(\times\) 5) and 3 m turbine tower radius; (**b**) 25 turbines (5 \(\times\) 5) and 4 m turbine tower radius; (**c**) 100 turbines (10 \(\times\) 10) and 3 m turbine tower radius; (**d**) 100 turbines (10 \(\times\) 10) and 4 m turbine tower radius.