Enhanced Information Security via Wave-Field Selectivity and Structured Wavefront Manipulation
Yufei Zhao, Deyu Lin, Qian Zhang, Haoyang Shi, Hong Niu, Afkar Mohamed Ismail, Yong Liang Guan, Chau Yuen
TL;DR
The paper targets secure, high-capacity wireless links by decoupling data and key transmission into two independent channels: a digital band-pass modulation (DBM) channel using orthogonal multi-mode vortex waves, and a spatial-field modulation (SFM) channel using a programmable metasurface (PMS) to encode encryption keys in the EM field distribution. It introduces a holographic, two-stage wavefront shaping method to route each vortex mode to distinct 3D focal spots, while a 2‑bit PMS enables dynamic, low-complexity key distribution via spatial energy patterns. A proof-of-concept prototype demonstrates reliable DBM data transmission and secure SFM key transfer with >15 dB crosstalk isolation between focal spots, confirming practical feasibility for secure IoT networks with limited processing and power. The approach offers scalable, low-complexity physical-layer security that leverages structured beamforming and mode-orthogonal multiplexing, potentially enabling secure, high-rate communications in dense IoT deployments.
Abstract
In this paper, we propose a novel secure wireless transmission architecture that enables the co-existence of spatial field modulation (SFM) and digital bandpass modulation (DBM), utilizing multi-mode vortex waves and programmable meta-surfaces (PMS). Distinct from conventional joint modulation schemes, our approach establishes two logically independent transmission channels--SFM and DBM--thereby eliminating the need for joint signal design or time synchronization. Specifically, the orthogonality of vortex wave modes is exploited to construct a high-capacity multi-mode DBM channel, in which each mode carries modulated symbols independently. As the composite waveform passes through the PMS, energy from different vortex modes is spatially focused onto distinct positions, dynamically determined by the PMS configuration. This spatial mapping forms a unique lookup table that encodes additional information in the electro-magnetic (EM) field distribution, effectively enabling a second, concurrent SFM channel. To enhance physical-layer security, the DBM channel transmits encrypted symbols transformed via dynamic symbol-domain mapping, while the corresponding mapping relations--or key information--are carried by the SFM channel. This lightweight dual-channel encryption strategy provides strong confidentiality without requiring complex joint decoding. To validate the feasibility of the proposed architecture, we design and implement a proof-of-concept prototype system, and conduct experimental demonstrations under real-world wireless communication conditions. The experimental results confirm the effectiveness of the co-existent DBM-SFM design in achieving reliable and secure transmission. The proposed architecture offers a scalable, low-complexity, and secure transmission solution for future IoT networks, especially in scenarios demanding both spectral efficiency and physical-layer confidentiality.