## 1 Introduction  
Wireless sensor networks (WSNs) are crucial in transforming urban cities into smart cities by utilizing sensor nodes to monitor environmental parameters and transmit data to a central sink node. These sensor nodes detect changes in the surroundings, enabling applications such as environmental monitoring, smart infrastructure management, healthcare, and public safety. However, urban deployments face limited energy resources, data security concerns, network scalability, and environmental factors. The focus is on leveraging suitable network architectures and topologies to address these challenges and enhance urban systems, including transportation systems, energy grids, water supply networks, communication networks, waste management systems, and more. The design and implementation of network architectures and topologies within these systems are crucial for addressing various challenges and enhancing their efficiency, resilience, and sustainability. Figure 1 provides a comprehensive overview of WSNs, highlighting their advantages, diverse applications, key challenges, and performance analysis criteria. It visually summarizes the essential aspects discussed in this survey, offering insights into the effectiveness and limitations of WSNs in real-world scenarios. The motivation behind deploying WSNs in urban areas lies in optimizing data collection, analysis, and decision-making processes to create smarter and more connected urban environments. By strategically integrating sensor nodes, sink nodes, network architectures, and topologies, WSN deployments can effectively overcome the challenges posed by urban environments. This strategic integration helps mitigate signal interference, space limitations, and energy-efficiency issues, ensuring the seamless operation of WSN applications in urban settings. WSN applications in urban areas are designed to address specific problems faced by urban environments. For example, in environmental monitoring, WSNs can help detect pollution levels, monitor air quality, and manage waste disposal, all of which contribute to a healthier urban environment. In smart infrastructure management, WSNs enable the real-time monitoring of critical infrastructure, such as bridges, roads, and buildings, helping prevent accidents and minimize maintenance costs. Similarly, in healthcare and public safety, WSNs can facilitate remote patient monitoring, emergency response coordination, and surveillance, ensuring timely interventions and improving overall urban safety and well-being. In general, the focus is on deploying WSNs to address challenges and problems in urban areas, ultimately leading to more efficient, sustainable, and livable cities. Various WSN architectures and topologies are utilized in different applications based on their requirements. Figure 2 shows the different types of network architectures and network topologies in WSN. The mesh topology, for example, stands out for its ability to provide redundant paths for data transmission, ensuring continuous communication even in the presence of node failures. This redundancy improves reliability, making mesh topologies particularly suitable for critical applications such as transportation systems, where uninterrupted communication is essential for dynamic routing management and  
systematically deploying sensor nodes in the monitoring area. However, the grid topology may require more nodes and infrastructure than other topologies, resulting in increased deployment costs and power consumption. Alternatively, circular topologies with a central sink node can offer efficient data aggregation and transmission, but they may be limited in scalability and coverage range due to the fixed communication radius from the central node. In general, the selection of the network topology and architecture in WSNs is driven by the specific requirements of each application, balancing factors such as reliability, scalability, cost, and power efficiency to optimize performance and functionality.