The proliferation of Internet of Things (IoT) devices has become the backbone of modern smart cities, enabling applications from intelligent traffic management to environmental monitoring. A critical challenge in these large-scale deployments is the constrained energy resources of sensor nodes, which are often battery-powered and deployed in hard-to-access locations. The routing protocol, which governs how data travels from source to destination, plays a pivotal role in determining the network's energy consumption and overall lifetime. This paper provides a comprehensive analysis of energy-efficient routing protocols specifically designed for IoT-based smart city applications. We categorize these protocols into flat-based, hierarchical-based, and location-based routing schemes, examining their core mechanisms, advantages, and limitations. Through a detailed comparative analysis based on key metrics such as energy consumption, scalability, latency, and network lifetime, we identify the most suitable protocols for various smart city scenarios. Furthermore, we present simulated performance results demonstrating the energy efficiency of hierarchical protocols like LEACH. The paper concludes by discussing future research directions, including the integration of machine learning and energy harvesting techniques to create more sustainable and resilient IoT networks for smart urban environments.
Guruswamy TB (Tue,) studied this question.