Abstract
As a promising physical layer security technique, physical layer key generation (PLKG) enables legitimate users to obtain secret keys from wireless channel without security infrastructures. However, in harsh propagation environments, the channel characteristic becomes unsatisfactory, the key generation rate (KGR) is significantly deteriorated. In this paper, we propose a novel fluid antenna (FA) enabled PLKG system to address this challenge. Specifically, we first derive the closed-form expression of the KGR for FA array, and then jointly optimize the precoding matrix and the antenna positions via a particle swarm optimization (PSO) algorithm. Next, to further reduce the computational complexity of the optimization procedure, we develop an alternating optimization (AO) algorithm, which combines the projected gradient descent (PGD) and the PSO. Simulation results demonstrate that by exploiting the additional spatial degree of freedom (DoF), our FA enabled PLKG system is superior to the benchmarks, such as the conventional fixed-position antenna (FPA) array and the reconfigurable intelligent surface (RIS). It is worth highlighting that compared to the conventional uniform planar antenna (UPA), the FA enabled PLKG achieves a 35.42\% KGR performance improvement under PSO algorithm and a 67.73\% KGR performance improvement under AO algorithm, respectively.
Abstract (translated)
作为一种有前景的物理层安全技术，物理层密钥生成（PLKG）使合法用户能够从无线信道中获取秘密密钥，而不依赖于任何安全基础设施。然而，在恶劣传播环境中，信道特性变得不佳，导致密钥生成率（KGR）显著下降。为此，本文提出了一种新颖的流体天线（FA）增强型PLKG系统来应对这一挑战。 具体而言，我们首先推导了FA阵列的闭式KGR表达式，并通过粒子群优化算法联合优化预编码矩阵和天线位置。接下来，为了进一步降低优化过程中的计算复杂度，我们开发了一种交替优化（AO）算法，该算法结合了投影梯度下降法（PGD）和粒子群优化算法。 仿真结果表明，在利用额外的空间自由度后，我们的FA增强型PLKG系统在性能上优于基准方案，如传统的固定位置天线（FPA）阵列以及可重构智能表面（RIS）。尤其值得注意的是，与传统均匀平面阵列（UPA）相比，基于FA的PLKG在使用PSO算法时，KGR性能提升了35.42%，而在采用AO算法时，则达到了67.73%的提升。
URL
https://arxiv.org/abs/2509.00018
