混合近场与远场通信中的宽带物理层安全
Wideband Physical Layer Security in Mixed Near-Field and Far-Field Communications
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中文总结 AI 辅助
针对混合近远场宽带通信，提出联合设计发射波束成形与人工噪声的优化方案，并开发低复杂度算法，以提升多用户保密速率。
中文摘要 AI 辅助
以往关于宽带物理层安全（PLS）的研究大多只关注远场或近场通信系统。在本文中，我们研究了一个更一般且实用的混合近场与远场宽带通信场景中的PLS，其中配备超大规模阵列（XL-array）的基站（BS）为远场中的多个合法用户提供服务，而一个近场窃听者试图在近距离截获机密信息。具体而言，我们构建了一个优化问题，通过联合设计发射波束成形和人工噪声（AN），在每子载波功率约束下，最大化所有合法用户在所有子载波上的保密速率。为了深入理解混合场宽带PLS的独特特性，我们首先分析了一个包含单个合法用户和单个窃听者的特例。有趣的是，我们表明混合场宽带系统中的安全传输区域在所有子载波上并不相同，这是由从菲涅耳积分推导出的子载波特定保密条件所揭示的。此外，我们从理论上证明，在系统中引入频率选择性AN带来两个关键好处：1）它将原本不安全的子载波转变为安全的子载波；2）它显著提升了整体保密性能。对于一般的多用户场景，我们提出了一种高效的两阶段混合波束成形算法，以联合设计发射波束成形和AN，确保在混合场条件下的安全传输。基于我们的分析见解，我们进一步开发了一种高效且低复杂度的算法，该算法通过直接将AN波束成形器与窃听者的信道对齐来设计它们，从而无需在所有子载波上优化AN波束成形器。
英文摘要
Prior studies on wideband physical layer security (PLS) have mostly focused on either far-field or near-field communication systems. In this paper, we investigate PLS in a more general and practical mixed near-field and far-field wideband communication scenario, where a base station (BS) equipped with an extremely large-scale array (XL-array) serves multiple legitimate users in the far field, while a near-field eavesdropper attempts to intercept confidential information at close range. Specifically, we formulate an optimization problem to maximize the secrecy rate of all legitimate users across all subcarriers by jointly designing the transmit beamforming and artificial noise (AN), subject to per-subcarrier power constraints. To gain useful insights into the unique characteristics of mixed-field wideband PLS, we first analyze a special case with a single legitimate user and an eavesdropper. Interestingly, we show that the secure transmission regions in mixed-field wideband systems are not the same across all subcarriers, as revealed by subcarrier-specific secrecy conditions derived from the Fresnel integrals. Moreover, we theoretically demonstrate that introducing frequency-selective AN into the system offers two key benefits: 1) it transforms originally insecure subcarriers into secure ones, and 2) it substantially improves the overall secrecy performance. For the general multiuser setup, we propose an efficient two-stage hybrid beamforming algorithm to jointly design the transmit beamforming and AN, ensuring secure transmission under mixed-field conditions. Building on our analytical insights, we further develop an efficient and low-complexity algorithm that designs the AN beamformers by directly aligning them with the eavesdropper's channel, thereby eliminating the need to optimize AN beamformers across all subcarriers.
发表机构
- City University of Hong Kong（香港城市大学）
- Southern University of Science and Technology (SUSTech)（南方科技大学）
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