## 4 Computational Simulations and Experimental Results
### Hardware Experimental Testing
#### 4.3.3 LOS Communication BER Testing  
In addition to the NLOS scattering communication experiment, outdoor LOS communication experiments were conducted. The positions of the transmitter and receiver were located at the two points indicated in Figure 12. The transmission distance was 500 m. Figure 12a illustrates the positions of the transmitter and receiver, while Figure 12b depicts the outdoor testing environment.  
In Figure 12a, \"TX\" represents the transmitter location, and \"Total 500 m\" indicates that the straight-line distance from the transmitter to the receiver is 500 meters. In mboxfigfig:photonics-2951484-f012b, \"TX\" stands for the transmitter, and \"RX\" stands for the receiver. \"PC\" refers to the computer used for data transmission, \"UV system\" represents the prototype of the experimental system, and \"DC-power supply\" is used to provide the voltage and current required for the prototype. \"Portable power station\" is an outdoor power source used to power various electrical devices.  
The outdoor field test results are displayed in Table 2. Out of a total of 241,664 transmitted data bits, 59 bits were found to be erroneous, resulting in a BER of \(2.45\times 10^{-4}\). Subsequently, the experimenter conducted BER tests for the communication system at different distances, ranging from 400 m to 700 m.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Values** \\ \hline Transmission Range & 500 m \\ Height of Obstacle & 1 m \\ UV Light Wavelength & 254 nm \\ System Rate & 5 kbps \\ Number of Error bits & 59 \\ Total Number of bits & 241,664 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Parameters and results of outdoor LOS field test.  
Figure 12: LOS test diagram: (**a**) the positions of the transmitter and receiver; (**b**) test site and equipment.  
Based on Figure 13, it is observed that within the range of 400 m to 500 m, the increase in BER is relatively slow. However, as the distance further increases, the BER exhibits a more significant upward trend. It can be observed that both experimental and simulation results exhibit similar trends of variation, with the simulated BER still outperforming the experimental BER. Moreover, as the distance increases, the gap between them tends to widen gradually.  
The deviation between the simulation and experimental results can be primarily attributed to the following reasons:  
1. When the particle density in the air is high, multiple scattering may occur. In the simulation, a single-scattering model was employed, which inevitably introduces certain deviations. UV photons interact with the abundant atmospheric molecules and aerosol particles. These two factors lead to increased path loss, resulting in poorer experimental BER data compared to the simulation results.
2. Due to the challenge of precisely matching the wavelength of the mercury lamp emission source with the filter, some photons are lost at the receiver, reducing reception efficiency and losing some signal photon energy. Prolonged operation of the emitter leads to a rapid local temperature rise, causing a decrease in the efficiency of mercury lamp emission. These two factors reduce reception efficiency, thereby affecting the experimental BER performance.