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.

中文翻译：

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通过大型智能表面进行无源波束成形和信息传输

大型智能表面 (LIS) 已成为一种有前途的新解决方案，可提高无线网络的能量和频谱效率。LIS 由大量低成本、近乎无源的可重构反射元件组成，通过反射撞击电磁波来增强无线通信。在这封信中，我们通过对 LIS 元素的索引采用空间调制，提出了一种新颖的无源波束成形和信息传输 (PBIT) 技术，其中 LIS 同时增强主要通信（通过无源波束成形）并将其私有数据发送到接收器（通过空间调制）。我们开发了一种无源波束成形方法来提高平均接收信噪比 (SNR)。我们还在接收器处建立了一个两步法来检索来自发射器和 LIS 的信息。数值结果表明，所提出的 PBIT 系统，尤其是经过优化的无源波束成形，明显优于没有 LIS 增强的系统。此外，还证明了无源波束成形增益和 LIS 信息率之间的权衡。