Integrated cooperative SWIPT THz-NOMA and secure DLTs for efficient 6G communications

Abstract

This thesis concentrated on advancing the performance of 6G communications and networks, evaluating efficiency, reliability, resource management, cost-effectiveness, energy consumption, user fairness, and security. Key enabling technologies and intelligent techniques, including terahertz (THz) frequency bands, nonorthogonal multiple access (NOMA), energy harvesting, cooperative networking (decode-and-forward relaying), and artificial intelligence were explored to achieve the targeted objectives. Cooperative simultaneous wireless information and power transfer (SWIPT) in THz-NOMA (and hybrid-NOMA) were integrated to overcome challenges in THz communications. Besides, the proposed deep learning-based 6G channel estimation (CE) model established a robust system against intelligent attacks associated with intelligent systems. The research highlighted the significant improvements achieved by these technologies, showcasing a 70% enhancement in wireless transmission performance for 6G communications compared to existing systems. The proposed cooperative SWIPT THz-NOMA system demonstrated noteworthy improvements in energy efficiency (EE), spectral efficiency (SE), and other critical metrics. Utilizing the proposed technologies resulted in a remarkable improvement over conventional cooperative networking. Additionally, the investigation extended to exploring cooperative SWIPT THz multiple-input multiple-output (MIMO) NOMA, introducing path-selection mechanisms and reliable transmission strategies. That outperformed the basic THz-NOMA and provided more enhancement in terms of SE and EE. The entire study emphasized a simpler design, reduced transceiver hardware (which accordingly reduced energy consumption, complexity, and cost), and improved reliability compared to previous work. Furthermore, this work addressed the imperfections in successive interference cancellation (SIC) in 6G NOMA-based communications, proposing an optimized two-user pairing scheme with SWIPT and cooperative hybrid-NOMA (H-NOMA) in THz communications. It presented a system performance improvement of 75% in SE and EE compared to conventional NOMA and orthogonal multiple access techniques. Moreover, the work focused on upgrading 5G communication systems to be 6G-compatible and meet the 6G stringent requirements of emerging technologies/applications. It addressed challenges in THz transmission, improving wireless connectivity, resource availability, processing, robustness, and capacity. It evaluated the best pairing strategy in H-NOMA, investigating all the possible SWIPT pairs with the available line-of-sight users to optimize the best pair/performance. Finally, the last part addressed CE vulnerability to adversarial attacks in 6G systems. The proposed deep autoencoder-based 6G CE model demonstrated robustness against adversarial attacks, providing a promising solution for securing 6G networks. System security and accuracy were validated through simulations, presenting an added value to the field.