# Outdoor Visible Light Communication in Intelligent Transportation Systems: Impact of Snow and Rain
## 3 Simulation Results and Discussion
### Bit Error Rate (BER)  
The BER performance versus the coverage area is displayed in Figure 13 for different weather turbulences under different modulation schemes for the first lane. Table 7 shows the maximum achievable distance for the different modulation schemes at a BER of \(10^{-6}\) and a data rate of 10 Mbps. It is observed that OOK achieves higher distances than SC-BPSK under different attenuation conditions but at the price of SNR, as shown in Figure 11. The L-PPM can cover distances greater than I-LPPM, but the choice in SNR performance is for I-LPPM, as shown in Figure 11. It is also observed in Table 7 that the Marshall model at light rain intensity can cover distances almost at very clear weather or higher. The reason behind this is that the Marshall model underestimates light rain intensities and (drizzles); so, it exhibits an attenuation behavior that is similar to very clear weather or less. The Marshall model is only an average distribution, which made it not accurate.  
Table 7 summarizes the maximum achievable distance for different modulation schemes in different weather conditions.  
It is also observed that as the modulation size increases, the maximum distances for reliable transmission decrease in I-LPPM, while in L-PPM, the maximum distances increase. The curves are broken almost at small distances (\(<\)18 m). This is because the receiver cannot capture the transmitted signal being almost under the traffic light.  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Weather Condition**} & \multicolumn{8}{c}{**Maximum Distance [m]**} \\ \cline{3-10}  & & **OOK** & **SC-BPSK** & **4 PPM** & **I-4 PPM** & **8 PPM** & **1-8 PPM** & **16 PPM** & **I-16 PPM** \\ \hline \multirow{3}{*}{Wet snow} & Very-Clear & & 173 & 123 & 202 & 156 & 222 & 140 & 237 & 125 \\ \cline{2-10}  & & 2 & 128 & 97 & 144 & 117 & 155 & 107 & 162 & 98 \\  & Precipitation level mm/h & 4 & 108 & 84 & 120 & 100 & 128 & 92 & 134 & 84 \\  & & 8 & 88 & 69 & 96 & 81 & 101 & 75 & 105 & 69 \\ \hline \multirow{3}{*}{Dry Snow} & \multirow{3}{*}{Precipitation level mm/h} & 2 & 95 & 75 & 105 & 89 & 111 & 82 & 116 & 75 \\  & & 4 & 60 & 47 & 63 & 54 & 66 & 51 & 69 & 47 \\  & & 8 & 32 & 20 & 32 & 27 & 34 & 24 & 35 & 19 \\ \hline \multirow{3}{*}{Marshall} & \multirow{3}{*}{Precipitation level mm/h} & 2 & 177 & 125 & 207 & 159 & 228 & 143 & 244 & 127 \\  & & 10 & 166 & 119 & 192 & 150 & 211 & 136 & 224 & 121 \\  & & 25 & 150 & 110 & 172 & 137 & 186 & 125 & 197 & 112 \\ \hline \multirow{3}{*}{France} & \multirow{3}{*}{Precipitation level mm/h} & 2 & 160 & 116 & 185 & 145 & 201 & 131 & 214 & 117 \\  & & 10 & 134 & 100 & 151 & 123 & 163 & 112 & 172 & 102 \\  & & 25 & 113 & 87 & 125 & 104 & 134 & 96 & 140 & 88 \\ \hline \multirow{3}{*}{Japan} & \multirow{3}{*}{Precipitation level mm/h} & 2 & 154 & 113 & 178 & 141 & 193 & 127 & 205 & 114 \\  & & 10 & 112 & 93 & 137 & 112 & 147 & 103 & 154 & 94 \\ \cline{1-1}  & & 25 & 102 & 79 & 112 & 94 & 119 & 87 & 124 & 80 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Maximum distance for different modulation schemes under various weather conditions.  
Figure 13: _Cont._In case of using \(\theta<40^{\circ}\) and FOV \(>40^{\circ}\), the maximum achievable distance for some modulation schemes such as I-LPPM and SC-BPSK may be so small or near zero. The incident angle \(\psi\) depends on \(\theta\); at the same time, \(\psi\) must be less than or equal to the FOV angle to be captured.