A Comprehensive Review of Trust and Reputation-Based Routing Protocols in Wireless Sensor Networks (WSNs): Models, Challenges, and Future Directions

Abstract

Wireless Sensor Networks (WSNs) are widely used in areas such as environmental monitoring, smart cities, and healthcare. However, due to their open and resource-limited nature, they are highly vulnerable to various security threats, especially from internal malicious nodes. Trust and reputation-based routing has become a popular solution to improve the reliability and security of data transmission in WSNs without relying heavily on encryption. This review paper presents an overview of recent developments in trust-based routing protocols. It classifies different models based on how trust is calculated, the types of trust considered (like direct, indirect, energy, and behavior-based), and how routing decisions are made. The paper also compares traditional lightweight approaches with more advanced machine learning and blockchain-based methods. Key challenges such as detecting smart attacks, maintaining energy efficiency, and adapting to dynamic environments are discussed. Finally, the paper outlines open issues and future research directions for building more secure, adaptive, and energy-efficient trust-aware routing in WSNs.