Joint Precoding and Phase Shift Design in Reconfigurable Intelligent Surfaces-Assisted Secret Key Generation
Joint Precoding and Phase Shift Design in Reconfigurable Intelligent Surfaces-Assisted Secret Key Generation
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DOI：
10.1109/tifs.2023.3268881
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发表时间：
2022-07
影响因子：
6.8
通讯作者：
Tianyu Lu;Liquan Chen;Junqing Zhang;Chen Chen-Chen;A. Hu
中科院分区：
文献类型：
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作者：
Tianyu Lu;Liquan Chen;Junqing Zhang;Chen Chen-Chen;A. Hu
物理层密钥生成（PLKG）是在资源受限的合法用户之间建立对称密钥的一种很有前途的技术。然而，PLKG在信道随机性受限的恶劣环境中遭受低密钥速率。为了解决这个问题，可重构智能表面（RIS）被引入到重塑信道通过控制大量的反射元件，它可以提供更多的信道多样性。在本文中，我们设计了一个信道探测协议，以充分提取级联信道的随机性，即，通道通过反射元件。我们推导了密钥速率的解析表达式，并设计了一个基于Karush-Kuhn-Tucker（KKT）条件的注水算法来找到上界。为了找到最佳的预编码和相移矩阵，我们提出了一种基于格拉斯曼流形优化方法的算法。该系统的关键率，比特不一致率（BDR）和随机性方面进行评估。仿真结果表明，我们的协议显着提高密钥速率相比，现有的协议。与没有RIS的多天线系统相比，当单元边长为1/4波长，Rician因子为0 dB时，我们提出的方法实现了平均9.51 dB的性能增益。
Physical layer key generation (PLKG) is a promising technique to establish symmetric keys between resource-constrained legitimate users. However, PLKG suffers from a low key rate in harsh environments where channel randomness is limited. To address the problem, reconfigurable intelligent surfaces (RISs) are introduced to reshape the channels by controlling massive reflecting elements, which can provide more channel diversity. In this paper, we design a channel probing protocol to fully extract the randomness from the cascaded channel, i.e., the channels through reflecting elements. We derive the analytical expressions of the key rate and design a water-filling algorithm based on the Karush-Kuhn-Tucker (KKT) conditions to find the upper bound. To find the optimal precoding and phase shift matrices, we propose an algorithm based on the Grassmann manifold optimization methods. The system is evaluated in terms of the key rate, bit disagreement rate (BDR) and randomness. Simulation results show that our protocols significantly improve the key rate as compared to existing protocols. Compared to multiple-antennas systems without a RIS, our proposed method achieves an average 9.51 dB performance gain when the side length of an element is 1/4 wavelength and the Rician factor is 0 dB.