# Evaluation of Deployment Challenges of Wireless Sensor Networks at Signalized Intersections
## 3 Simulation Results  
Once the simulation scenario has been defined, simulation results can be obtained. These results have been validated with real measurements which have been made in a campaign of measurements in the same scenario, which is shown in Section 4. For the simulations, 16 antennas have been placed in the considered scenario, one for each traffic light. The specific position of the antennas in the scenario is shown in Figure 4. To reduce interferences with people and vehicles, each antenna has been placed 10 cm above each traffic light. The radiating element is a wireless ZigBee more which has been configured as a dipole, transmitting 18 dBm at 2.41 GHz. Simulation parameters are shown in Table 2. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **Permittivity (\(\mathbf{\epsilon_{r}}\))** & **Conductivity (\(\mathbf{\
u}\)) (S/m)** \\ \hline Air & 1 & 0 \\ Concrete & 25 & 0.02 \\ Aluminum & 4.5 & \(4\times 10^{7}\) \\ Polypropylene & 3 & 0.11 \\ Brick & 4.44 & 0.11 \\ Glass & 6.06 & \(10^{-12}\) \\ Plasterboard & 2.02 & 0 \\ Grass & 30 & 0.01 \\ Trunk Tree & [37] & [37] \\ Tree foliage & [37] & [37] \\ Human body model & [32] & [32] \\ Car model & [38] & [38] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Material properties in the RL simulation. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Frequency & 2.41 GHz \\ Transmitted Power Level & 18 dBm \\ Vertical plane angle resolution \(\Delta\theta\) & \(2^{\circ}\) \\ Horizontal plane angle resolution \(\Delta\varphi\) & \(2^{\circ}\) \\ Reflections & 6 \\ Cuboids size & 2 m \\ \hline \hline \end{tabular}
\end{table} 
Table 2: 3D Ray Launching simulation parameters. Figure 3: Real (**left**) and schematic (**right**) view of the considered scenario for simulation in the 3D Ray Launching Algorithm. Figures 5 and 6 shows the power distribution within the considered scenario for different heights and planes, and for different sensors placed in different traffic lights. As it can be seen, the influence of the obstacles (like the trees, streetlights, buildings, etc.) can be easily appreciated. It is shown that the morphology as well as the topology of the considered scenario has a noticeable impact on radio wave propagation. Figure 4: Schematic view of the position of the different antennas within the considered scenario. Figure 5: Estimation of received power (dBm) on the considered scenario (\(XY\) planes) for different heights obtained by the 3D Ray Launching algorithm (**a**) 1.4 m height for the sensor #1; (**b**) 3 m height for sensor #1; (**c**) 1.4 m height for sensor #6; (**d**) 3 m height for sensor #6. Figure 7 shows the different zones of estimated received power extracted from the data of Figure 5a,c. It can be seen that received power results are accurate but not homogeneous, and because of that, the radio planning task has an important role. Different values of the mean received power are obtained depending of the obstacle density of the different zones. Table 3 show the different values of power mean with its standard deviation and the obstacle density of the zone considered. It can be seen that the obstacle density has great influence in received power, but it is also relevant to consider the area of the considered zone and the distance from the transmitter of each zone. From these results, it is shown that received power in different points of the scenarios depends greatly of the position of the transmitter, the obstacle density of the different zones and the different material properties of the obstacles. An important radioelectric phenomenon in this type of environment is given by multipath propagation. To illustrate this fact, the delay spread for the whole scenario and the power delay profile for the central location of the scenario has been obtained and it is shown in Figures 8 and 9, respectively. The delay spread has been defined as the time delay between the first and the last ray which arrives to each spatial point.