## 4 Applications of WSN in Urban Areas
### Gas Monitoring Applications
The results demonstrated the effectiveness of the proposed gas detection method in enhancing detection capabilities and in providing valuable insights for improving safety and environmental protection measures. [PERSON] et al. (2023) [43] introduced a deep learning feature engineering-based approach to establish the relationship between underground sensors for gas detection. The study utilized Zigbee-based antenna types and underground sensors and employed a combination of decentralized and star-connected network topologies. The research aimed to address challenges related to determining the link between underground sensors and analyzing gas concentration data effectively. By employing deep learning techniques and feature engineering approaches, the study proposed innovative solutions to enhance the accuracy and reliability of underground gas detection systems. The results demonstrated the effectiveness of the proposed approach in identifying sensor malfunctions and analyzing gas concentration data, providing valuable insights for improving underground gas detection systems' performance and reliability in various applications, including mining and tunneling operations. [PERSON] et al. (2022) [44] introduced a fast operando monitoring technique for fast gas evolution monitoring, addressing the need for efficient and accurate detection of gas emissions. The designed technique utilized Zigbee-based antenna types along with a non-dispersive infrared multi-gases sensor, enabling comprehensive gas detection capabilities. Employing a combination of centralized network and mesh network topology, the research aimed to overcome challenges associated with traditional gas monitoring methods, such as limited coverage and detection speed. By leveraging real commercial batteries and establishing correlations between gas concentrations, voltage, and temperature, the designed technique provides innovative solutions to enhance the efficiency and reliability of gas evolution monitoring. The results demonstrated the effectiveness of the proposed technique in rapidly detecting gas emissions and providing valuable insights for improving safety measures and environmental monitoring in various industrial and commercial settings. [PERSON] et al. (2022) [45] developed an optically powered and safe gas monitoring scheme aimed at detecting environmental gases in underground mines, addressing the critical need for reliable gas monitoring in hazardous environments. The system utilized Zigbee-based antenna types alongside liquid-crystal-based optical transducer sensors, allowing for accurate gas detection under ambient temperature and pressure conditions. By employing a combination of centralized network and mesh network topology, the research aimed to overcome challenges related to power supply and data transmission in underground environments. The system achieved reliable and efficient gas monitoring capabilities by leveraging key technologies, including power-over-fiber (PoF), for efficient power delivery and information transmission. Through an ultra-low power consumption design, the study proposed solutions to enhance the safety and effectiveness of gas monitoring systems in underground mining operations. The results demonstrated the feasibility and effectiveness of the optically powered gas monitoring scheme in detecting environmental gases and ensuring the safety of underground mine environments. [PERSON] et al. (2021) [46] investigated a gas distribution pipeline network model for addressing the critical need in efficient data transmission and monitoring. The study utilized Zigbee-based antenna types alongside pressure and temperature sensors, enabling accurate and real-time monitoring of gas pipelines. Employing a combination of centralized network and cluster-based network topology, the research aimed to optimize data transmission and network efficiency in pipeline monitoring applications.