The frequency bands between 7 and 24 GHz, also known as upper midband or Frequency Range (FR) 3, are being considered as an enabler of 6th Generation (6G) mobile networks. This portion of the spectrum exhibits different propagation characteristics compared to frequencies above 24 GHz, while also offering the potential to provide larger bandwidth allocations for mobile systems than those available in the sub-6 GHz range. 6G technology and spectrum policy, however, will need to guarantee coexistence with the incumbents that already use these frequency bands, which include a variety of services, from radiolocation to satellite-based communications, remote sensing, and radioastronomy. In this paper, we consider the challenge of coexistence between 6G terrestrial systems and satellite incumbents in different portions of the FR3 bands. Using a large-scale 3D model of a terrestrial deployment in the city of Boston and an open-source ray tracing solution, we evaluate the level of Radio Frequency Interference (RFI) that tens of terrestrial Next Generation Node Bs (gNBs) generate toward satellites at different elevation angles. Our model, based on realistic obstruction, clutter, diffraction, and reflections, shows that sidelobes and Non-Line-of-Sight (NLoS) paths can significantly contribute to RFI. Besides directionality, the spatial distribution of gNBs also plays a key role in defining the RFI levels, suggesting that a careful design and operation of terrestrial deployments can create coexistence opportunities.

翻译：频率在7至24 GHz之间的频段，也称为上中频段或频率范围（FR）3，正被视为第六代（6G）移动网络的重要推动力。与24 GHz以上的频率相比，该部分频谱表现出不同的传播特性，同时也有潜力为移动系统提供比sub-6 GHz频段更宽的带宽分配。然而，6G技术和频谱政策需要确保与已经使用这些频段的现有业务共存，这些业务包括从无线电定位到卫星通信、遥感以及射电天文学等多种服务。在本文中，我们探讨了6G地面系统与现有卫星业务在FR3频段不同部分共存所面临的挑战。通过使用波士顿市大规模三维地面部署模型和开源射线追踪解决方案，我们评估了数十个地面下一代节点B（gNB）在不同仰角下对卫星产生的射频干扰（RFI）水平。我们的模型基于现实中的遮挡、杂波、衍射和反射，表明旁瓣和非视距（NLoS）路径可能显著增加RFI。除了方向性外，gNB的空间分布在定义RFI水平方面也起着关键作用，这表明对地面部署进行谨慎设计和操作可以创造共存机会。