The electromagnetic spectrum plays a fundamental role in the development of the digital society. It enables wireless communications (either between humans or machines) and sensing (for example, for Earth exploration, radio astronomy, imaging, and radars). While each of these uses benefits from a larger bandwidth, the spectrum is a finite resource. This introduces competing interests among the different stakeholders of the spectrum, which have led—so far—to rigid policies and spectrum allocations. Recently, the spectrum crunch in the sub-6-GHz bands has prompted communication technologies to move to higher carrier frequencies, where future sixth-generation (6G) wireless networks can exploit theoretically very large bandwidths. However, the spectrum above 100 GHz features several narrow, yet numerous subbands that are exclusively allocated for passive sensing applications, e.g., for climate and weather monitoring. This prevents the allocation of large contiguous bands to active users of the spectrum, either being communications (which need tens of gigahertz of bandwidth to target terabit-per-second links) or radars. This article explores how spectrum policy and spectrum technologies can evolve to enable sharing among different stakeholders in the above 100-GHz spectrum, without introducing harmful interference or disrupting either security applications or fundamental science exploration. This portion of the spectrum presents new challenges and opportunities for the design of spectrum sharing schemes, including higher spreading and absorption losses, extremely directional antenna technologies, and ultrahigh data-rate communications, among others. This article provides a tutorial on current regulations above 100 GHz and highlights how sharing is central to allowing each stakeholder to make the most out of this spectrum. It then defines—through detailed simulations based on standard International Telecommunications Union (ITU) channel and antenna models—scenarios in which active users may introduce harmful interference to passive sensing. Based on this evaluation, it reviews a number of promising techniques that can enable active/passive sharing above 100 GHz. The critical review and tutorial on policy and technologies of this article have the potential to kickstart future research and regulations that promote safe coexistence between active and passive users above 100 GHz, further benefiting the development of digital technologies and scientific exploration.

中文翻译：

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100 GHz 以上的共存和频谱共享


电磁频谱在数字社会的发展中发挥着基础性作用。它支持无线通信（人与机器之间）和传感（例如，地球探索、射电天文学、成像和雷达）。虽然这些用途中的每一种都受益于更大的带宽，但频谱是有限的资源。这引入了频谱不同利益相关者之间的利益竞争，迄今为止，这导致了严格的政策和频谱分配。最近，6 GHz 以下频段的频谱紧缩促使通信技术转向更高的载波频率，未来的第六代 (6G) 无线网络理论上可以利用非常大的带宽。然而，100 GHz 以上的频谱具有几个狭窄但数量众多的子频带，专门分配给无源传感应用，例如气候和天气监测。这阻止了将大的连续频段分配给频谱的活跃用户，无论是通信（需要数十千兆赫的带宽来瞄准每秒太比特的链路）还是雷达。本文探讨了频谱政策和频谱技术如何发展，以实现上述 100 GHz 频谱中不同利益相关者之间的共享，而不引入有害干扰或破坏安全应用或基础科学探索。这部分频谱为频谱共享方案的设计带来了新的挑战和机遇，包括更高的扩频和吸收损耗、极其定向的天线技术和超高数据速率通信等。 本文提供了有关 100 GHz 以上现行法规的教程，并强调了共享对于让每个利益相关者充分利用该频谱的核心作用。然后，通过基于标准国际电信联盟 (ITU) 信道和天线模型的详细模拟，它定义了主动用户可能对被动传感引入有害干扰的场景。基于此评估，它回顾了许多可以实现 100 GHz 以上有源/无源共享的有前途的技术。本文对政策和技术的批判性评论和教程有可能启动未来的研究和法规，促进 100 GHz 以上的主动和被动用户之间的安全共存，进一步有利于数字技术和科学探索的发展。