# A Hybrid Scheme for Disaster-Monitoring Applications in Wireless Sensor Networks
## 7 Conclusions and Future Work  
In disaster-monitoring scenarios, real-time accurate information with uninterrupted monitoring is crucial. In this study, we first present a collaborative disaster-monitoring system based on WSNs, and show the entire architecture of the system. Then, we obtain seismic data in a highly energy-efficient manner, based on the compressed sensing method. In this study, a superior node hybrid scheme, HT-MAC, for disaster monitoring in wireless sensor networks is proposed, and the operating procedures of clustering and data transmission are presented. The proposed clustering algorithm for heterogeneous networks can effectively extend the network's lifetime. HT-MAC operates in duty cycle mode at the steady-state stage, and ordinary nodes transmit multimedia data based on a virtual token ring. During each period, seismic data are promptly transmitted when each superior node is polled. Owing to the relatively short active state of the sensor nodes, the alert data are transmitted with a low-power listening and shortened preamble approach during the sleep state to satisfy the delay requirement. HT-MAC can simultaneously satisfy the requirements of three types of data for disaster-monitoring applications. These three typesof data are ordinary data with high throughput, seismic data with high throughput and low delay, and alert data with high reliability and low delay of tens of milliseconds. HT-MAC must support reliable transmission, even in abnormal situations, and the handling procedures for abnormal situations are described in detail. Based on embedded Markov chains, a model of the HT-MAC scheme was developed, and the mean queue length, mean cycle time, and mean upper bound of the frame delay were obtained. A simulation model of HT-MAC was built, and the simulation results verified the theoretical analysis. Using the simulation models of HT-MAC and pLEACH, the HT-MAC clustering algorithm significantly outperformed the pLEACH algorithm and increased the lifetime of the network. Based on the simulations of WirelessHART and DRX, the frame delay performance of HT-MAC was better than that of WirelessHART and DRX. We found that the mean delay of the superior and alert data was far less than that of the ordinary data, and a low delay level was maintained, especially when the traffic intensity was heavy. The alert data have a maximum frame delay of 15 ms, and HT-MAC provided a data rate of several hundred kb/s for superior and ordinary data. These results satisfy the requirements of disaster-monitoring applications. As the next step, we will establish a testbed to analyze and validate the HT-MAC scheme. Technological advances have enabled the development of disaster-monitoring systems [13]; collaborative disaster-monitoring systems can be widely used in earthquake early warning and rescue, volcanic eruption early warning and monitoring, landslide early warning, and other disaster-monitoring applications. In the future, we will implement collaborative disaster-monitoring systems in order to perform seismic monitoring. Practical application of HT-MAC may significantly improve our ability to cope with disasters. Conceptualization, D.C. and Y.Z. ; methodology, D.C.; software, Y.Z., G.P. and L.D. ; validation, D.C., G.P. and L.D. ; formal analysis, D.C.; investigation, D.C. and Y.Z. ; resources, G.P. and Y.Z. ; data curation, G.P. and L.D. ; writing--original draft preparation, D.C. and Y.Z. ; writing--review and editing, D.C. and Y.Z. ; visualization, Y.Z. ; supervision, F.G.; project administration, D.C., Y.Z. and G.P. ; funding acquisition, D.C., Y.Z. and G.P. All authors have read and agreed to the published version of the manuscript. This research was funded by the Special Fund of Fundamental Scientific Research Business Expense for Higher School of Central Government (Projects for creation teams), grant number ZY20215106, and the Langfang Science and Technology Research Self-Funded Project, grant number 2022011004 and grant number 2022011033. Not applicable.