Open access peer-reviewed chapter
Abstract
Objectively, the conventional radio frequency (RF) are already overcrowded and could not afford the diverse emerging services, including augmented reality, mixed reality, 8K video, and self-driving vehicles. For addressing the upcoming capacity demand and performance metric challenges of 6G networks, it is essential to explore and integrate the novel free space optical (FSO) techniques and wireless communications techniques to inherit the complementary fundamental characteristics simultaneously. On one hand, FSO techniques are license-free, inherent physically secure, and relatively low in infrastructure costs. On the other hand, the wireless communication techniques are capable of providing sufficient robustness, ubiquitous coverage, and higher maturity. Therefore, for designing and developing the future-oriented 6G networks, the researchers from the academic and industry community consistently make contribution and proposed novel schemes, the relevant topics and important analysis of which is touched included by the each chapters of this book, from the view of the FSO and wireless communication separately.
Keywords
- free space optical communications
- beam characteristics
- wireless communications
- 6G networks
- optical beams
1. Introduction
According to the commercial forecasting, the global mobile traffic is expected to be more than 5000 EB/month, and the predictable number of connected devices on the Internet will be up to 500 billion devices by 2030. Therefore, the conventional radio frequency (RF) networks are already overcrowded and could not satisfy the quality of service of 6G network independently [1, 2, 3, 4]. For tackling the above challenges, considering the available radio spectrum is getting nearly saturated, diverse free space optical (FSO) techniques have been proposed and are becoming one promising solution to conventional RF network paradigm [5, 6, 7]. The charming and unique features of FSO include hundreds of terahertz of unlicensed optical spectrum, high security, electromagnetic interference-free operation, and simple implementation. At the same time, considering the disadvantages such as limited coverage and easy to be blocked for the FSO network alone, the novel wireless communication techniques must be consistently investigated to achieve reliable and seamless coverage simultaneously.
2. Novel free-space optical communications for future-oriented 6G networks
For further enhancing the transmission capacity performance of the FSO system for the evolving 5G and future-oriented 6G wireless networks, the wavelength division multiplexing (WDM) technique is introduced to FSO system in the presence of wireless and optical nonlinearities. Moreover, for typical indoor application scenarios, the researchers are actively exploring the superior performance features of laser-based wireless communications, compared to the conventional light-emitting diodes-based wireless communications with limited several tens MHz modulation bandwidth. As for outdoor lane scenario, the fundamental channel characteristic is compared between the distinct non-Lambertian LED beam and Lambertian LED beam configurations for 6G wireless networks, for evaluating the effect of spatial optical beams on vehicle FSO performance.
3. Novel wireless communications for future-oriented 6G networks
Similarly, the antenna systems and antenna mutual coupling are vital to the performance improvement of future-oriented 6G networks as well. Mutual coupling in the context of antennas presents a substantial and pressing concern within the realm of 5G and 6G wireless communication systems. In particular, one innovative method is proposed by the researcher in this book to minimize mutual coupling between antennas without permanent alteration of the structure. In addition, advancements in antenna systems are systematically reviewed for beyond 5G (B5G) and anticipated 6G. The concerned antenna aspects include microstrip antennas, metamaterial-based designs, reconfigurable antennas, phased array antennas, and lens antennas.
Acknowledgments
This work is supported by the National Natural Science Foundation of China (Grants No. 62061043), the Natural Science Foundation of the Xinjiang Uygur Autonomous Region (Grants No. 2019D01C020), and the Tianshan Cedar Project of Xinjiang Uygur Autonomous Region (Grants No. 202101528).
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