THz Communications: A Catalyst for the Wireless Future
THz Communications: A Catalyst for the Wireless Future
复制标题
太赫兹通信：无线未来的催化剂
DOI：
10.1109/mcom.2020.9269507
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
T. Nagatsuma
中科院分区：
文献类型：
--
作者：
A. Alexiou;Sergey D. Andreev;Gábor Fodor;T. Nagatsuma
随着无线世界向 6G 迈进，无线电 Tbit/s 通信以及支持的接入和回程网络基础设施预计将成为主要技术趋势。然而，某些严重的限制影响了未来无线通信系统满足高数据速率、接近零延迟以及高频谱和能源效率的联合要求的能力。在这种情况下，利用太赫兹频段进行无线传输，作为光纤的延伸，是弥合这一差距并提供超越 5G 的无处不在的高速互联网接入的有希望的推动者。此外，私营和工业部门中越来越多的移动和固定用户将需要数百 Gbit/s 的连接到蜂窝塔或蜂窝塔之间（回程）或蜂窝塔与远程无线电头端（前传）之间的连接。在这种情况下，除了 Tbit/s 量级的数据速率之外，关键参数还包括通信范围以及在合理的资本和运营支出下可实现的频谱和能源效率。利用太赫兹频段进行接入和回程连接带来了独特且新颖的挑战，因此有必要重新考虑几种传统的通信和网络机制。这些挑战的根本原因是太赫兹无线电链路的超宽带和高方向性以及信号和天线设计、信道和干扰建模以及硬件限制方面的其他太赫兹通信特性。由于窄波束而产生的无线电干扰结构根本不同，因此需要对干扰进行彻底的表征和详细的建模。基于过去的传播和通道建模研究，应考虑视线和非视线反射和散射分量的贡献，以及固有的分子噪声、未对准损伤和阻塞概率。媒体访问控制和无线电资源管理协议需要使用笔形波束进行操作，因此必须基于全新的原理。快速切换过程需要结合发现、定位和跟踪功能所需的时间。 Tbit/s 的数据速率给收发器处理带来了巨大的挑战，其中包括算法和架构设计以及硬件实现。受太赫兹技术塑造无线通信未来的潜力的推动，本专题旨在确定基带处理方面的关键技术差距和可行的推动因素。其中包括射频前端和天线设计；传播和信道建模；波形、信号和编码；波束成形和（超大规模）MIMO；以及资源管理和媒体访问控制方案。最重要的是，本专题旨在阐明各利益相关者（包括现有参与者和新参与者）对太赫兹通信采用的潜在加速器或阻碍因素。在此过程中，它提供了有关太赫兹体制中原型设计、实施挑战以及标准化和监管问题的见解。第一篇文章“对垂直异构网络的太赫兹传播和通道建模的整体研究”，作者：Kürşat Tekbıyık、Ali Rıza Ekti、Güneş Karabulut Kurt、Ali Görçin 和 Halim Yanikomeroglu，提出了一种最近提出的垂直异构网络架构 在大量采用不同通信技术的小蜂窝的情况下，包括地球静止轨道和低地球轨道卫星和网络飞行平台以及地面通信链路，回程/前程。太赫兹通信的提出是为了实现这种异构系统概念。由于太赫兹链路提供大带宽，从而实现超高数据速率，因此该解决方案适用于小型蜂窝的回程和前程，支持从卫星间链路到体内纳米网络的众多应用。准确的信道建模被认为是此类系统概念可行性的关键。为此，测量活动的结果揭示了太赫兹通信在垂直异构网络架构中的真正潜力。 Kari Rikkinen、Pekka Kyösti、Marko E. Leinonen、Markus Berg 和 Aarno Pärssinen 撰写的题为“太赫兹无线电通信：面向 6G 的链路预算分析”的文章通过考虑天线和射频硬件技术以及无线电传播挑战，通过链路预算评估来评估和量化太赫兹无线电的潜力。可实现或所需的噪声系数、发射功率和天线增益是主要的关注参数。从射频角度来看，观察到的瓶颈出现在在非常高的天线增益的支持下产生足够高的发射功率和低噪声的过程中。例如，作者分析了 300 GHz 频率在 30 GHz 带宽、10 m 链路距离上为不同类型的设备支持 100 Gbit/s 数据速率的情况。 Vitaly Petrov、Thomas Kürner 和 Iwao Hosako 撰写的题为“IEEE 802.15.3d：面向 6G 的亚太赫兹频段通信的首次标准化工作”的文章介绍了 IEEE 802.15.3d 内的标准化活动，IEEE 802.15.3d 是对 802.15.3 的修订，旨在促进亚太赫兹频段消费者无线通信的标准化。 IEEE 802.15.3d 解决了距离从几十厘米到几百米的点对点交换连接，其数据速率为 100 Gbit/s 或更高。介绍了物理和介质访问层的目标应用和使用场景以及关键设计原则，以及初始性能结果。这些结果表明第五代无线系统有实质性改进，从而为第六代太赫兹网络铺平了道路。 THZ 通信：无线未来的催化剂
A the wireless world moves toward 6G, radio Tbit/s communications and the supporting access and backhaul network infrastructures are expected to become a predominant technology trend. However, certain severe limitations affect the capability of future wireless communications systems to meet the joint requirements of high data rate, near-zero latency, and high spectral and energy effi ciency. In this context, utilizing THz frequency bands for wireless transmissions, as an extension to optical fi ber, is a promising enabler to bridge this gap and provide ubiquitous high-speed Internet access beyond 5G. Moreover, an increasing number of mobile and fi xed users in the private and industry sectors will require hundreds of Gbit/s for connectivity to or between cell towers (backhaul) or between cell towers and remote radio heads (fronthaul). In such scenarios, critical parameters, apart from the data rates in the order of Tbit/s, are the communications range and the achievable spectral and energy effi ciency at reasonable capital and operational expenditures. Utilizing the THz frequency bands for access and backhaul connectivity brings unique and novel challenges that make it necessary to rethink several conventional communications and networking mechanisms. The root cause of these challenges is the ultra-wideband and highly directional nature of THz radio links and other THz communications peculiarities, in terms of signal and antenna design, channel and interference modeling, and hardware constraints. The fundamentally diff erent structure of radio interference due to narrow beams calls for a thorough characterization and detailed modeling of interference. Building on past propagation and channel modeling studies, contributions of the line-of-sight and non-line-of-sight refl ected and scattered components should be considered, as should be the inherent molecular noise, misalignment impairments, and blockage probability. Medium access control and radio resource management protocols need to operate with pencil beams and must therefore be based on radically new principles. Fast handover procedures need to incorporate the time required for discovery, localization, and tracking functionalities. The Tbit/s data rates create signifi cant challenges in transceiver processing, which include algorithm and architecture design as well as hardware implementation. Motivated by the potential of THz technologies to shape the future of wireless communications, this feature topic seeks to identify the critical technology gaps and the feasible enablers in terms of baseband processing. These include radio frequency frontend and antenna design; propagation and channel modeling; waveforms, signals, and coding; beamforming and (ultra-massive) MIMO; as well as resource management and medium access control schemes. Most importantly, this feature topic aims to shed light on the potential accelerators or showstoppers in the adoption of THz communications as viewed by the various stakeholders, both incumbents and newcomers. In doing so, it provides insights on prototyping, implementation challenges, and standardization and regulatory matters in the THz regime. The fi rst article, “A Holistic Investigation of Terahertz Propagation and Channel Modeling toward Vertical Heterogeneous Networks,” by Kürşat Tekbıyık, Ali Rıza Ekti, Güneş Karabulut Kurt, Ali Görçin, and Halim Yanikomeroglu, presents a recently proposed vertical heterogeneous network architecture for backhaul/fronthaul in the case of a large number of small cells of diff erent communications technologies, including geostationary Earth orbit and low Earth orbit satellites and networked flying platforms, along with terrestrial communications links. THz communications are proposed to enable this heterogeneous system concept. As THz links offer large bandwidth, leading to ultrahigh data rates, this solution is suitable for backhauling and fronthauling of small cells that support numerous applications from inter-satellite links to in-vivo nanonetworks. Accurate channel modeling is considered key for the feasibility of such system concepts. To this end, measurement campaign fi ndings are reported to reveal the true potential of THz communications in vertical heterogeneous network architectures. The article entitled “THz Radio Communication: Link Budget Analysis toward 6G,” by Kari Rikkinen, Pekka Kyösti, Marko E. Leinonen, Markus Berg, and Aarno Pärssinen, assesses and quantifi es the potential of THz radio by considering antenna and radio frequency hardware technologies and radio propagation challenges, by means of link budget evaluations. The achievable or required noise fi gure, transmit power, and antenna gain are the main parameters of interest. From the RF viewpoint, the observed bottlenecks occur in the generation of suffi ciently high transmit power and low noise with the support of very high antenna gains. For example, the authors analyze the case of 300 GHz frequency to support 100 Gbit/s data rate at 30 GHz bandwidth on 10 m link distance for diff erent kinds of devices. The article entitled “IEEE 802.15.3d: First Standardization Eff orts for Sub-Terahertz Band Communications toward 6G” by Vitaly Petrov, Thomas Kürner, and Iwao Hosako, presents the standardization activities within IEEE 802.15.3d, an amendment to 802.15.3 established to facilitate standardization of consumer wireless communications in the sub-THz frequency band. IEEE 802.15.3d addresses switched point-to-point connectivity with data rates of 100 Gbit/s and higher at distances ranging from tens of centimeters up to a few hundred meters. Target applications and usage scenarios and key design principles for the physical and the medium access layers are presented, along with initial performance results. These results indicate substantial improvements over fi fth-generation wireless systems, thus paving the way toward sixth generation THz networks. THZ COMMUNICATIONS: A CATALYST FOR THE WIRELESS FUTURE