Passive Information Transmission in Intelligent Reflecting Surface Aided MISO Systems

Intelligent reflecting surface (IRS) is emerging as a revolutionary technology, which can construct favorable wireless propagation environment by tuning a large number of low-cost passive reconfigurable elements. Different from the prior works that focus on enhancing the spectrum or energy efficiency of wireless communications, this letter introduces a novel passive information transmission scheme in IRS-aided multi-input single-output (MISO) systems. While IRS enhances the primary base-station (BS)-to-user communication, it also simultaneously delivers additional secondary information to the user. To achieve this goal, the secondary information is embedded into the primary signals by adjusting the phase shifts of IRS elements according to the secondary symbols to be sent. Aiming at this goal, we design joint beamforming and reflecting optimization algorithm to minimize the transmit power while guaranteeing the qualities of both primary and secondary transmissions. Simulation results demonstrate the effectiveness of the proposed IRS-aided passive information transmission.