## 5 Discussion  
This review provides a comprehensive consolidation of the key enabling technologies necessary for realizing the Future Internet and 6G wireless networks. The technologies examined, including beamforming, massive MIMO, reconfigurable intelligent surfaces (RIS), terahertz communications, wireless energy harvesting, digital twins, and advanced antenna systems, each contribute uniquely to the evolving landscape of wireless communication. However, significant interdisciplinary challenges persist. Beamforming techniques have advanced substantially, with hybrid and adaptive solutions enabling efficient wideband communication. Nevertheless, real-world deployment faces major hurdles, including architectural complexity, beam squint effects due to the lack of wideband tunable devices, and the need for ultra-fast beam management in dynamic environments. These limitations underscore the urgent need for novel beamforming methods that combine low complexity and power consumption with precise, multibeam control to achieve scalable, low-latency, energy-efficient performance. Massive MIMO systems are foundational to the capacity and reliability gains envisioned for 6G. However, practical implementations remain constrained by energy consumption and hardware complexity. In mmWave communications, a compromise between high-gain beams and MIMO diversity is necessary to overcome the highly lossy environment. These challenges highlight the need for intelligent hybrid analog-digital designs and machine learning-driven beam management strategies to enable feasible massive MIMO deployments. Figure 21: Concept of fluid antenna [327]. RIS technologies offer promising means for cost-effective manipulation of the wireless environment. However, the realization of dynamically controllable metasurfaces or selective frequency surfaces at practical scales remains nontrivial. Key challenges include low-latency reconfiguration, seamless integration with existing infrastructure, power optimization, and accurate channel estimation. Furthermore, the absence of standardized deployment models limits wide adoption. Embedding sensing capabilities and simplifying unit cell control will be crucial for real-time adaptability and computational efficiency. Terahertz communications open access to vast underutilized spectral resources but introduce fundamental challenges, including high propagation losses, sensitivity to blockages, and atmospheric absorption. Addressing these constraints requires not only high-gain antenna innovations but also the development of efficient channel models, transceiver architectures, and multiple access schemes tailored to the impairments of THz bands. Wireless energy harvesting and power transfer are pivotal for sustainable Internet of Everything (IoE) applications. Yet, existing solutions are limited by poor energy conversion efficiency and matching losses, especially under variable received power conditions. Novel energy harvester topologies and advanced nonlinear techniques are needed to optimize utilization of the vast RF spectrum and ensure efficient power transfer. Digital twins hold transformative potential for wireless network design, offering real-time predictive management, virtual prototyping, and enhanced operational resilience. However, they introduce challenges such as real-time data synchronization, massive data handling, and scalable virtualization. Addressing these issues will require novel architectural frameworks and AI-enhanced analytics. Antennas, fundamental to all the technologies discussed, face increasing demands for efficiency, miniaturization, reconfigurability, and integration. Innovations are required across user equipment, base stations, satellites, UAVs, and RIS-based systems to support multiband, multibeam, energy-efficient operation at mmWave and THz frequencies. Persistent challenges include phase noise, nonlinearities, THz miniaturization, and massive array integration, all under constraints of real-time adaptability, ultra-low latency, and high reliability.