Secure Terahertz Communication with Intelligent Reflecting Surface and Energy Harvesting

In this paper, an intelligent reflecting surface (IRS)-assisted secure terahertz (THz) communication system is investigated, in which an access point (AP) emits confidential information to its legal user in the presence of multiple eavesdroppers. The legal user adopts the power splitting (PS)–based energy harvesting (EH) model to achieve the simultaneous transmission of information and energy. To maximize the achievable secrecy rate, the transmit beamformer, the reflecting matrix at IRS, and the PS ratio are jointly designed. To solve the formulated nonconvex problem, an alternate optimization (AO) algorithm is proposed based on Taylor expression and semidefinite relaxation (SDR) method. Simulation results reveal that the proposed energy harvesting-empowered secure THz communication scheme can simultaneously improve the system secrecy rate and achieve the user's energy harvesting demand.