Conventional wireless communication suffers from inherent security risks due to indiscriminate information transmission. Directional information modulation (DIM) offers a solution by generating correct constellation symbols in desired directions and distorting them in undesired directions. Existing DIM schemes have limitations in bulkiness, energy consumption, cost, and 2D/high-order modulation support. This paper proposes a DIM scheme using a 2-bit programmable metasurface (PM) to overcome these limitations. A discrete optimization algorithm optimizes digital coding sequences, enabling multi-directional beam generation and transmission of correct constellation symbols. The scheme successfully realizes 8PSK, 16QAM, and 64QAM constellations in multi-channel modes, demonstrating a significant advancement in physical-layer security for communication systems.

Hui Xu, Jun Wei Wu, Zheng Xing Wang, Rui Wen Shao, Han Qing Yang, Tie Jun Cui