Title: Fluid Antenna System-assisted Physical Layer Secret Key Generation Show Chinese title

Title: 基于流体天线系统的物理层秘密密钥生成

Abstract: This paper investigates physical-layer key generation (PLKG) in multi-antenna base station systems, by leveraging a fluid antenna system (FAS) to dynamically customize radio environments. Without requiring additional nodes or extensive radio frequency chains, the FAS effectively enables adaptive antenna port selection by exploiting channel spatial correlation to enhance the key generation rate (KGR) at legitimate nodes. To comprehensively evaluate the efficiency of the FAS in PLKG, we propose an FAS-assisted PLKG model that integrates transmit beamforming and sparse port selection under independent and identically distributed and spatially correlated channel models, respectively. Specifically, the PLKG utilizes reciprocal channel probing to derive a closed-form KGR expression based on the mutual information between legitimate channel estimates. Nonconvex optimization problems for these scenarios are formulated to maximize the KGR subject to transmit power constraints and sparse port activation. We propose an iterative algorithm by capitalizing on successive convex approximation and Cauchy-Schwarz inequality to obtain a locally optimal solution. A reweighted $\ell_1$-norm-based algorithm is applied to advocate for the sparse port activation of FAS-assisted PLKG. Furthermore, a low-complexity sliding window-based port selection is proposed to substitute reweighted $\ell_1$-norm method based on Rayleigh-quotient analysis. Simulation results demonstrate that the FAS-PLKG scheme significantly outperforms the FA-PLKG scheme in both independent and spatially correlated environments. The sliding window-based port selection method introduced in this paper has been shown to yield superior KGR, compared to the reweighted $\ell_1$-norm method. It is shown that the FAS achieves higher KGR with fewer RF chains through dynamic sparse port selection. Show Chinese abstract

Abstract: 本文研究了多天线基站系统中的物理层密钥生成（PLKG），通过利用流体天线系统（FAS）动态定制无线环境。 无需额外节点或大量射频链路，FAS通过利用信道空间相关性，有效实现自适应天线端口选择，以提高合法节点的密钥生成速率（KGR）。 为了全面评估FAS在PLKG中的效率，我们提出了一种FAS辅助的PLKG模型，在独立同分布和空间相关信道模型下分别集成发射波束成形和稀疏端口选择。 具体而言，PLKG利用互易信道探测来推导基于合法信道估计之间互信息的闭式KGR表达式。 针对这些场景，提出了非凸优化问题，以在发射功率约束和稀疏端口激活条件下最大化KGR。 我们提出了一种迭代算法，利用连续凸近似和柯西-施瓦茨不等式来获得局部最优解。 应用了一种重加权$\ell_1$-范数的算法，以促进FAS辅助PLKG的稀疏端口激活。 此外，提出了一种低复杂度的滑动窗口端口选择方法，以替代基于瑞利商分析的重加权$\ell_1$-范数方法。 仿真结果表明，FAS-PLKG方案在独立和空间相关环境中均显著优于FA-PLKG方案。 本文引入的基于滑动窗口的端口选择方法相比重加权$\ell_1$-范数方法表现出更优的KGR。 结果显示，FAS通过动态稀疏端口选择，在较少射频链路的情况下实现了更高的KGR。