WSN Routing Protocols: A Clear and Comprehensive Review

Wireless Sensor Networks (WSNs) have emerged as a fundamental technology in modern applications, including environmental monitoring, smart cities, healthcare, and industrial automation. Efficient routing plays a crucial role in ensuring network longevity, energy efficiency, and reliable data transmission, given the inherent constraints of WSNs, such as limited energy, processing power, and dynamic topologies. Over the years, various routing protocols have been proposed to address these challenges, each designed to optimize performance based on different criteria. This paper provides a comprehensive yet concise review of WSN routing protocols, offering a broader classification than previous studies by integrating multiple taxonomies from the literature. Unlike existing reviews that may either be too detailed or overly general, this study presents a structured and accessible overview that balances depth and clarity. Key routing challenges, including energy efficiency, scalability, and security, are discussed, followed by a detailed classification of routing protocols based on network structure, data delivery mode, path establishment, application type, and next-hop selection strategies. By merging diverse classification schemes into a unified framework, this review aims to provide researchers and practitioners with a clear, well-organized perspective on the current state of WSN routing. The insights presented in this study can serve as a foundation for future research and the development of more adaptive and efficient routing solutions for WSNs.