Energy-Efficient and Low-Latency Routing Protocols in Iot Networks: A Comprehensive Literature Review and Critical Analysis

The rapid expansion of Internet of Things (IoT) networks has introduced significant challenges in the design of routing protocols, particularly in achieving a balance between energy efficiency and communication latency. This paper presents a thorough literature review of energy-efficient and low-latency routing protocols for IoT networks, examining more than 200 selected publications from 2020 to December 2023. We developed a systematic taxonomy that categorizes protocols into energy-efficient, latency-optimized, and balanced approaches, assesses their performance characteristics, and pinpoints critical research gaps. Our analysis indicates that while energy-efficient protocols can enhance the network lifetime by up to 60%, recent machine learning-driven methods show up to a 59% reduction in the busiest-node routing energy while maintaining over 99% reliability. Latency-optimized solutions have achieved up to a 35.5% reduction in end-to-end delays through opportunistic forwarding and deep reinforcement learning. However, significant challenges persist in terms of security integration, real-world validation, and standardization. We offer a comprehensive roadmap for future research directions, highlighting the integration of artificial intelligence, edge computing, and next-generation network technology. This review serves as a foundation for researchers and practitioners developing advanced IoT routing solutions.