Passive Beamforming and Information Transfer via Large Intelligent Surface

Abstract

Large intelligent surface (LIS) has emerged as a promising new solution to improve the energy and spectrum efficiency of wireless networks. A LIS, composed of a large number of low-cost nearly-passive reconfigurable reflecting elements, enhances wireless communications by reflecting impinging electromagnetic waves. In this letter, we propose a novel passive beamforming and information transfer (PBIT) technique by adopting spatial modulation on the index of the LIS elements, in which the LIS simultaneously enhances the primary communication (by passive beamforming) and sends its private data to the receiver (by spatial modulation). We develop a passive beamforming method to improve the average receive signal-to-noise ratio (SNR). We also establish a two-step approach at the receiver to retrieve the information from both the transmitter and the LIS. Numerical results show that the proposed PBIT system, especially with the optimized passive beamforming, significantly outperforms the system without LIS enhancement. Furthermore, a tradeoff between the passive-beamforming gain and the information rate of the LIS has been demonstrated.