Razor-sharp Narrowbeam Communications and Management for Terahertz Wireless Networks (Invited Paper)

Terahertz (THz) wireless communications are promising for future 6G wireless systems by providing multi-ten-GHz bandwidth. To overcome the limited transmission distance problem, ultra-massive multi-input-multi-output (UM-MIMO) systems with 1024 planar array of antennas that generates high gain razor-sharp beams with 3dB beamwidth of 3.16° are proposed, leading that THz wireless networks are accompanied with good and bad of narrowbeam communications. In this paper, challenges and features on THz narrowbeam communications are introduced, which include requirements of precise beam alignment on millidegree and fast tracking in milli-second with low hardware cost and power consumption, the THz-specific beam squint effect and specific hybrid beamforming structures. The existing methods for narrowbeam communications in the literature are reviewed, with analysis on their shortcomings to THz networks. Inspired by THz distinctive directional communications, several THz narrow-beam communication solutions are further investigated. Finally, multiple open problems and potential research directions are elaborated, as a roadmap of THz narrowbeam wireless networks.