Spectrum Sharing for UAV Communications: Spatial Spectrum Sensing and Open Issues

Unmanned aerial vehicles (UAVs) are attracting increasing attention for applications such as video streaming, surveillance, and delivery using reliable line-of-sight (LOS) links. Nevertheless, due to the large radio-frequency (RF) transmission footprint from a UAV transmitted to ground nodes, UAV communications may significantly deteriorate the performance of cochannel ground communication links. With the lack of a dedicated spectrum, researchers need to design efficient spectrum-sharing policies for UAV communications to enhance spectral efficiency (SE) and control interference-to-ground communications. One technique for spectrum sharing is spatial spectrum sensing (SSS), which enables devices to sense spatial spectrum opportunities and reuse them aggressively and efficiently by controlling the SSS radius. The goal of this article is to introduce the fundamentals, challenges, and applications of SSS for UAV spectrum access and discuss open research problems for realizing UAV spectrum sharing, including dynamic spectrum access for swarm UAV networks, artificial intelligence (AI)-enabled UAV spectrum access, blockchain-based UAV spectrum access, multichannel access for UAVs, and the integration of UAVs into cellular networks.