Illegitimate intelligent reflective surfaces (IRSs) can pose significant physical layer security risks on multi-user multiple-input single-output (MU-MISO) systems. Recently, a DISCO approach has been proposed an illegitimate IRS with random and time-varying reflection coefficients, referred to as a "disco" IRS (DIRS). Such DIRS can attack MU-MISO systems without relying on either jamming power or channel state information (CSI), and classical anti-jamming techniques are ineffective for the DIRS-based fully-passive jammers (DIRS-based FPJs). In this paper, we propose an IRS-enhanced anti-jamming precoder against DIRS-based FPJs that requires only statistical rather than instantaneous CSI of the DIRS-jammed channels. Specifically, a legitimate IRS is introduced to reduce the strength of the DIRS-based jamming relative to the transmit signals at a legitimate user (LU). In addition, the active beamforming at the legitimate access point (AP) is designed to maximize the signal-to-jamming-plus-noise ratios (SJNRs). Numerical results are presented to evaluate the effectiveness of the proposed IRS-enhanced anti-jamming precoder against DIRS-based FPJs.

翻译：非法智能反射面（IRS）对多用户多输入单输出（MU-MISO）系统构成重大物理层安全威胁。近年来，一种名为DISCO的方法提出采用随机时变反射系数的非法IRS（称为"迪斯科"IRS，DIRS）。此类DIRS无需依赖干扰功率或信道状态信息（CSI）即可攻击MU-MISO系统，而传统抗干扰技术对基于DIRS的全被动干扰机（DIRS型FPJ）无效。本文针对DIRS型FPJ提出一种IRS增强型抗干扰预编码器，该方案仅需DIRS干扰信道的统计CSI而非瞬时CSI。具体而言，通过引入合法IRS来削弱合法用户（LU）处DIRS干扰信号相对于发射信号的强度，同时设计合法接入点（AP）的有源波束成形以最大化信干噪比（SJNR）。数值结果验证了所提IRS增强型抗干扰预编码器对抗DIRS型FPJ的有效性。