Wavefront Hopping: An Enabler for Reliable and Secure Near Field Terahertz Communications in 6G and Beyond

One of the principal differences between 5G-grade mobile millimeter wave (mmWave) and 6G (and beyond) terahertz (THz) band communications is the fact that the latter will often operate in the near field. This is because next-generation THz wireless solutions will have to keep the current physical size of the antenna systems or even increase them at the infrastructure side to combat spreading losses and maintain the desired performance and coverage for lower available transmit power and wider bands. A combination of a large antenna aperture and higher frequency increases the near-field zone around the transmitter. In the THz near field, the dexterity of wave propagation, characterized by the signal wave-front - the time-variant set of all points having the same phase - becomes important. The unique features and properties of these wavefronts provide an additional degree of freedom in system design. In this article, we present a novel concept of wavefront hopping to enable efficient, reliable, and secure THz band communications in the near field. Inspired by an existing “frequency hopping” concept, we show how a dynamic intelligent update of the utilized THz wavefront can work. We further illustrate how the use of this concept improves the characteristics of the THz link in various practical setups, and addresses some of the principal challenges of THz communications, thus making near-field THz communications more technologically and commercially attractive for 6G and beyond wireless networks.