# An Overview of Emergency Communication Networks
## 5 Sea Ad Hoc Network (SANET)
### Case Study: Broadband-Narrowband Emergency Communication Command System
The link coverage radius is shown in the following:  
\[\mathrm{L}=46.3+33.9\mathrm{lgf}-13.82\mathrm{lgh_{a}}-\mathrm{a(h_{m})}+(44.9 -6.55\mathrm{lgh_{a}})\mathrm{lgr}+\mathrm{C_{m}} \tag{2}\]  
where f is the frequency of the electromagnetic wave; \(\mathrm{h_{a}}\) is the antenna height of the base station; \(\mathrm{h_{m}}\) is the height of the base station; \(\mathrm{r}\) is the coverage radius of the base station; \(\mathrm{C_{m}}\) is the correction factor; \(\mathrm{a(h_{m})}\) is the height correction factor of the base station antenna. The specific parameter settings are shown in Table 6.  
The LTE edge rate was calculated by Formulas (1) and (2). The maximum uplink loss is 125.11 dB and the maximum downlink loss is 116.13 dB, that is, the uplink coverage radius is 2.58 km and the downlink coverage radius is 4.76 km. Therefore, in order to expand the coverage area of the system, the system will adopt the \"LTE + Mesh\" networking scheme. This uses the portable LTE base station to realize network coverage of the rescue site, and \begin{table}
\begin{tabular}{c c c} \hline \hline
**Base Station Parameters** & \multicolumn{2}{c}{**Terminal and Other Parameters**} \\ \hline Frequency point/Mhz & 1785–1805 & Transmit power/dBm & 23 \\ Bandwidth/Mhz & 20 & Antenna gain/dBi & 0 \\ Base station power/W & 20 & Antenna height/m & 1.4 \\ Antenna gain/dBi & 12 & Interference margin/dB & 2.72 \\ Antenna height/m & 40 & Receiving sensitivity/dBm & \(-\)121.21 \\ Cable feed loss/dB & 0.5 & Human body loss/dB & 0 \\ Minimum receiving sensitivity/dBm & 130.5 & Penetration loss/dB & 16 \\ Interference margin/dB & 0.89 & Shadow residue/dB & 8.06 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: System parameter settings. Figure 10: System topology of broadband-narrowband integrated emergency communication. the backpack mesh base station to transmit signals back to the front finger and rescue site. The network topology is shown in Figure 11.  
In response to the needs of emergency rescue communication services, the portable broadband-narrowband integrated emergency command system was set up in Dongcun, Ziwu Town, Chang'an District, Xi'an for practical testing, and the business transmission contents, such as voice dispatch, video dispatch, short message, and picture data packets, were tested. The test results show that the maximum distance of broadband-narrowband integrated communication of portable devices is about 18.78 km. The video communication distance of the LTE private network base station is about 3.56 km, and 16 channels of video can be pulled up at the same time. According to the network bandwidth limitation, the voice communication distance of the LTE private network base station is about 7.82 km. The maximum communication distance of point-to-point networking using a piggyback mesh base station is about 11.23 km. The system can be applied to a variety of scenarios, such as forest fire rescue, urban fire rescue, and emergency production accident rescue. Taking forest fire prevention as an example, the main rescue challenge is the signal coverage of the rescue site and the data transmission between the front and rear. Therefore, the portable broadband-narrowband integration emergency communication system can be used to realize voice, video, conference, and other services between the rescue site and the command center.