Wireless Sensor Networks: A Comprehensive Review of Architecture, Energy Optimization, and Tactical Challenges

Wireless Sensor Networks (WSNs) have emerged as a foundational technology for the realization of the Internet of Things (IoT), facilitating autonomous monitoring across industrial, medical, and environmental landscapes. Despite their proliferation, the operational longevity of WSNs is acutely bottlenecked by the finite energy reserves of individual sensor nodes. This paper provides a systematic, multi-dimensional review of WSN architectures, protocol stacks, and energy conservation paradigms. We synthesize literature spanning 2014–2022 to critically analyze the trade-offs between network throughput and power consumption. The review distinguishes itself by providing a granular comparison of hardware operational components and a robust performance mapping of routing protocols (LEACH, PEGASIS, TEEN). Our findings highlight a significant research shift from basic connectivity toward intelligent, self-sustaining networks. The paper concludes with an extensive roadmap of 20 future research directions to guide scholars toward unresolved challenges in energy harvesting and AI-driven network management.