Coexistence and Spectrum Sharing Above 100 GHz

Abstract

The electromagnetic spectrum plays a fundamental role for 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, among others). 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 6G wireless networks can exploit theoretically very large bandwidths. However, the spectrum above 100 GHz features several narrow, yet numerous sub-bands 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 paper 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 opportunities to design spectrum sharing schemes, based on novel antenna designs, directional ultra-highrate communications, and active/passive user coordination. The paper 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 paper 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.

Opportunistic Temporal Spectrum Coexistence of Passive Radiometry and Active Wireless Networks

“…Polese et al [7] investigate the allocation of large chunks of continuous bandwidths for future 6G wireless networks operating above 100 GHz, where multiple narrow passive sensing sub-bands scatter over the frequency spectrum, precluding the allocation of large continuous bandwidth chunks. In their work, they consider a wireless link between two terrestrial base stations interfering with an Earth Exploration Satellite Service (EESS) satellite.…”

“…One solution gaining attention is the use of passive bands for active wireless communications [7]. However, this increases the risk of active wireless devices inducing radio frequency interference (RFI) on passive sensing instruments.…”

“…One case that has been gaining attention in recent years involves the use of passive Radio Frequency (RF) bands, which are solely devoted to passive sensing applications such as remote sensing and radio astronomy, for active wireless communications. Specifically, the coexistence of terrestrial active wireless communications and Earth Exploration Satellite Services (EESS) is becoming a central topic of discussion [1]. A major question that needs to be answered is how and to what extent Radio Frequency Interference (RFI) would impact such EESS satellites.…”