Unleashing Massive Connectivity with 6G: From Enabling Technologies and Design Principles to AI-Driven Network Intelligence

The advent of sixth-generation (6G) technology heralds a new era in telecommunications, promising to revolutionize connectivity by addressing the limitations of its predecessors and introducing groundbreaking advancements. This paper gives a comprehensive overview of 6G, highlighting its potential to deliver unprecedented data rates, ultra-low latency and enhanced reliability. Unlike 5G, which primarily focuses on improving mobile broadband and IoT, 6G aims to integrate a wider range of services, including holographic communication, pervasive Artificial Intelligence (AI), Internet-of-Everything (IoE) and advanced edge computing. Research indicates that 6G will leverage technologies such as terahertz (THz) communication, intelligent reflecting surfaces (IRSs), optical wireless communication (OWC), visible light communication (VLC) and quantum communication, thereby enabling applications that were previously deemed impossible. These advancements are expected to support industries ranging from healthcare and education to smart cities and autonomous systems. However, challenges such as spectrum management, security, resource optimization and the environmental impact of 6G infrastructure remain significant. This paper synthesizes key insights from recent studies, providing a comprehensive overview of the technological 6G landscape, its convergence, potential applications, design challenges and the sustainable future research directions necessary to realize the full potential of 6G. Finally, the key takeaways for the readers are provided.