Towards Long-Lasting Nanoscale Wireless Communications in the Terahertz Band for Biomedical Applications

During the last decade, the research on nanotechnology and wireless communications in the terahertz band supported the design of pioneering biomedical applications. To counteract the very scarce amount of energy available for nano-devices, a current challenge is to develop energy-aware and energy harvesting mechanisms enabling long-lasting communications at the nanoscale. Many contributions in this direction envisage exploiting piezoelectric nanogenerators to retrieve energy from external vibrations (i.e., the human heartbeat) and use it for transmission purposes. Indeed, in line with the recent scientific achievements in this context, this paper investigates a power control mechanism based on the feedback control theory. The control law is conceived for managing the communication in human tissues, where nano-devices are equipped with a piezoelectric nanogenerator and transmit information messages through electromagnetic waves in the terahertz band. The amount of energy spent to transmit an information message is dynamically tuned by a proportional controller in a closed-loop control scheme which simultaneously considers harvesting and discharging processes. The whole system is analytically described with a nonlinear state equation. As well, it is presented the acceptable range of values of the proportional gain guaranteeing technological constraints and its asymptotic stability. Finally, a numerical evaluation shows the behavior of the proposed approach in a conceivable biomedical scenario.