## 4 Applications of WSN in Urban Areas
### Gas Monitoring Applications
Key challenges such as estimated network lifetime, node deployment strategies, energy harvesting from the field, and optimal sink node placement were addressed by evaluating different routing protocols for WSNs in pipeline monitoring. By studying the performance of various routing protocols, the research provided valuable insights into system adaptability and efficiency in gas pipeline monitoring applications, ultimately contributing to the development of more robust and reliable monitoring systems for critical infrastructure networks. Table 8 presents a comparison of methodologies for gas leakage and detection monitoring in various environments, detailing their objectives, sensor types, network configurations, results, and limitations. These methods utilize GPS sensors, gas sensors, underground sensors, non-dispersive infrared multi-gas sensors, liquid-crystal-based optical transducers, and pressure and temperature sensors within centralized or decentralized networks featuring hierarchical, cluster-based, star, and mesh topologies. The objectives include detecting gas leaks in urban areas, improving safety and environmental protection, identifying sensor relationships for gas detection, performing efficient gas emission detection, monitoring gases in underground mines, and efficiently monitoring gas distribution networks. The results show improved NL, E, Delay, R, T, and LR. However, limitations include reducing energy consumption, high complexity levels, unaddressed computational costs, and inefficiencies in time consumption for gas distribution monitoring. Each methodology addresses specific aspects of gas detection and monitoring but encounters distinct implementation challenges. The \(\diamondsuit\) in Table 8 shows that the method increases the performance of the particular metric, whereas the blank space indicates that the method does not consider the performance of the particular metric. The summary conclusions of gas monitoring applications are listed below. * Advanced gas monitoring systems address challenges in detecting gas leaks, enhancing safety, and improving environmental protection in urban and hazardous environments. * Centralized Network topologies, including Hierarchical and Mesh, offer comprehensive data collection and real-time monitoring, especially in large-scale urban and underground settings. They are efficient in data aggregation but may have high energy consumption and complexity. * Decentralized Network topologies, such as Cluster-based and Star, provide effective coverage and flexibility. The Cluster-based topology handles complex environments with multiple sensors, while the Star topology simplifies network management and reduces computational costs. * Advanced techniques like Deep Learning and Optically Powered Sensors enhance gas detection accuracy and efficiency but may face computational and energy challenges. * Each network topology has unique strengths and limitations. Mesh Network Topology is reliable and comprehensive for dynamic, large-scale monitoring, while Cluster-based and Star topologies offer specific efficiency, cost, and coverage benefits. These diverse approaches and network architectures enhance gas monitoring and detection, improving safety and environmental protection across various applications and environments.