## 2 Materials and Methods
### System Design
#### 2.1.2 Design of Local Self-Organizing Network Terminals  
Considering the urgency of the firefighting operation, the on-site firefighters need to go into action immediately once they enter the scene. Aggregating all the data using appropriate wireless communication technology before proceeding with satellite communications can greatly enhance efficiency. Table 1 lists some of the major wireless communication technologies that do not rely on cellular networks and their characteristics. Zigbee technology shows obvious advantages after considering the special needs of forest firefighting vehicle-mounted wireless communication networks. The low power consumption of forest firefighting vehicles, which may operate for tens of hours at a time, allows them to maintain communication networks for long periods of time. The self-organizing nature makes them particularly suitable for emergency firefighting operations. If a link fails and does not work, the operator does not have to spend extra time dealing with the problem; it will adjust its topology and find another suitable link on its own. In addition, the communication range of individual Zigbee devices is generally between 10 m and 30 m, while the distance of the parameter collection nodes with forest fire trucks as carriers is no more than 10 m, so the range of the Zigbee network link can meet the requirements of local area wireless network. From the outside, through the relay function of Zigbee devices and optimized layout, its coverage can be further extended. Therefore, the system is based on the Zigbee networking technology IEEE 802.15.4 protocol to establish a local self-organizing network. The Zigbee self-organizing network technology can quickly build a reliable emergency communication network at the fire scene. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \begin{tabular}{c} **Communications** \\ **Technology** \\ \end{tabular} & **Bluetooth** & **Wi-Fi** & **Zigbee** & **Z-Wave** & **LoRa** \\ \hline \begin{tabular}{c} General Connection \\ Distance \\ \end{tabular} & \(\leq\)10 m & \(\leq\)100 m & \(\leq\)20 m & \(\leq\)30 m & \(\leq\)5 km \\ \hline \begin{tabular}{c} Power Wastage \\ \end{tabular} & Medium & High & Low & Low & Low \\ \hline \begin{tabular}{c} Self-Organized or \\ Not \\ \end{tabular} & N & N & Y & Y & N \\ \hline \begin{tabular}{c} Common \\ Application \\ Scenarios \\ \end{tabular} & Proximity personal & \begin{tabular}{c} Multi-device \\ hole connectivity \\ \end{tabular} & \begin{tabular}{c} IoT devices and \\ high-speed \\ transmission \\ \end{tabular} & \
\begin{tabular}{c} Smart home and \\ environmental \\ monitoring \\ \end{tabular} &
\begin{tabular}{c} Remote sensor \\ networks \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Major wireless communication technologies and their characteristics. Figure 1: System architecture of vehicle-mounted emergency communication system based on BeiDou RSMC for firefighting operations in forest areas without a public network. The system uses channels in the 2.4 GHz band, and the ideal data transmission rate in this band is 250 Kb/s in the physical layer. The topology of the local self-organizing network is a tree structure, consisting of three end device nodes and one coordinator node. Figure 2a shows the distribution of Zigbee channels over the 2.4 GHz band. Figure 2b shows the four-layer structure of the Zigbee protocol stack. Figure 2c shows the logical structure between nodes of local self-organizing network. Each node uses a TI CC2530 as the main controller, which, as a system-on-chip (SOC) for 2.4 GHz IEEE 802.15.4, Zigbee, and RF4 CE, combines the performance of an RF transceiver, an industry-standard enhanced 8051 CPU, in-system programmable flash memory and 8 KB RAM, and many other powerful features [33; 34]. Meanwhile, the CC2530 incorporates the Zigbee protocol stack (Z-Stack(tm)).