## 3 Results and Discussion

Table 3: Simulation results of one-, two-, and three-shaft underground mine communication system availability. Figure 9: Availability rate of the communication system with a one-, two-, and three-shafts mine. The simulation was performed by doubling the current and corrective maintenance to the without standby communication system in one shaft underground mine and by combining corrective and preventative maintenance after a 50% increase in preventative maintenance. In the communication system without standby in the one-shaft underground mine, the current availability rate was 73.95%, and after increasing preventative maintenance by 50%, the availability rate was 81.26%, and 9.8% compared to the status. After doubling corrective maintenance, it was 85.27% and 15.6% compared to the status, and after combined corrective and preventative maintenance, it was 89.75% and 21.3% compared to the status (Figure 11 and Table 5) (see Supplementary Materials). \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline
**Site Link Availability Model (years)** & **0** & **1** & **2** & **3** & **4** & **5** & **6** & **7** & **8** & **9** & **10** \\ \hline \begin{tabular}{c} **Combined results of** \\ **improved corrective and** \\ **preventative maintenance** \\ **preventative maintenance** \\ **preventative maintenance** \\ **improved by 50\%** \\ \end{tabular} & 100 & 93.5 & 92 & 91.6 & 91.5 & 91.5 & 91.5 & 91.5 & 91.5 & 91.5 & 91.5 \\ \hline \begin{tabular}{c} **Preventative maintenance** \\ **improved by 50\%** \\ \end{tabular} & 100 & 93.5 & 89.7 & 87.5 & 86.2 & 85.4 & 85 & 84.7 & 84.6 & 84.5 & 84.4 \\ \hline \
\begin{tabular}{c} **Corrective maintenance** \\ **doubled** \\ \end{tabular} & 100 & 90.3 & 88.3 & 87.9 & 87.8 & 87.8 & 87.8 & 87.8 & 87.8 & 87.8 & 87.8 \\ \hline
\begin{tabular}{c} **Current** \\ \end{tabular} & 100 & 90.3 & 84.9 & 81.9 & 80.2 & 79.3 & 78.8 & 78.6 & 78.4 & 78.3 & 78.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Simulation results of site link availability. Figure 10: Results of the compared simulation of the site link. To improve the reliability of the communication system, a standby system is necessary. In the last part of the study, the results of the development using system dynamics modeling show how the reliability of the single- and dual-standby system is improved. According to the system dynamic model--which was developed during the study--and results of the simulations, the models fully achieved the originally set goals of improving the communication system's reliability. The results of this research are compared to previous studies. Our research dealt with the standby system and is based on the example of underground mine communication systems. This study is innovative in the way it is modeled and developed for each device and the system as a whole [5]. In addition, it studied single standby parallel systems and dual standby three-parallel systems. Weibull, Poisson, and exponential distribution were uniquely developed to model the system dynamics of a communication system [6]. Figure 11: Simulation results of the without standby communication system in one shaft underground mine.