Wurood Fadhil Abbas, Muhammad N. Jawad, Hamzah Hadi Qasim, Ola J. Saleh, Ahmed Kareem Lateef, Karrar Hassan Thamir, Abdulwahhab Essa Hamzah, Mahmood A. Al-Shareeda, Ahmed Hameed Majeed
The development speed of IoT applications has brought with it ultra-low delay, high reliability, large-scale access, and energy saving needs. 5G makes massive IoT possible, but new use cases like autonomous systems, XR, Industry 4.0, and smart cities are beyond what our networks can support today. 6G will solve these problems by leveraging advanced technologies, such as THz communication (TC), RIS, massive MIMO (mMIMO), ultra-dense networks (UDNs), and integrated space–air–ground links. The convergence of IoT with sixth generation (6G) wireless networks is envisioned to open a new era of smart, autonomous and ultra-connected things. Contrary to the past generations, 6G is expected to deliver ultra-low latency (sub-millisecond), extremely high throughput (terabit per second scale), massive connection of devices, integrated sensing and communication, and in-network AI natively. In this paper, we follow a systematic review methodology to analyze the state-of-the-art literature from 2020–2025, organize the examined works based on the types of communication technologies used, types of AI integration, security, QoS/URLLC support, and energy sustainability, and outline open challenges and research gaps. We, therefore, present a Broader cross-layer perspectives in terms of 6G-based IoT solutions by integrating the aspects of AI intelligence for sustainable communication solutions along with the support of network slicing, URLLC and management of a secure architecture in this paper. The significance of these technologies and the impact they can have for next-generation intelligent IoT applications are discussed, and finally open issues and future research directions towards IMT-2030 are presented.