We investigate the secure degrees of freedom (SDoF) of the multiple-input multiple-output (MIMO) wiretap channel with intersymbol interference (ISI) in the presence of a multi-antenna cooperative jammer. We focus on the practically relevant setting with no channel state information at the transmitters (CSIT). More specifically, the legitimate transmitter and the cooperative jammer only have statistical knowledge of the channel in terms of the effective number of ISI channel taps, i.e., channel impulse response (CIR) lengths, toward the legitimate receiver and the eavesdropper. Our main contribution is to show that in the absence of CSIT, positive SDoF can be achieved by carefully exploiting: 1) the heterogeneity of the CIR lengths toward both receivers and 2) the relative number of antennas at the four terminals. To achieve secrecy, we propose a scheme in which the transmitter strategically sends a mixture of information and artificial noise symbols in a way that exploits the heterogeneity of CIR lengths. Additionally, the cooperative jammer transmits artificial noise symbols in a way that completely masks all the information symbols that are received at the eavesdropping node. Under the proposed scheme, positive SDoF can be achieved, even when the number of antennas at the legitimate receiver is less than the number of antennas at the eavesdropper.

中文翻译：

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盲 MIMO 协作干扰：通过 ISI 异构性实现保密，无需 CSIT


我们研究了在存在多天线协作干扰器的情况下具有符号间干扰 (ISI) 的多输入多输出 (MIMO) 窃听通道的安全自由度 (SDoF)。我们专注于发射机处没有信道状态信息的实际相关设置（CSIT）。更具体地，合法发射机和协作干扰机仅具有针对合法接收机和窃听者的ISI信道抽头的有效数量（即信道脉冲响应（CIR）长度）方面的信道统计知识。我们的主要贡献是表明，在没有 CSIT 的情况下，可以通过仔细利用以下内容来实现正 SDoF：1）两个接收器的 CIR 长度的异质性和 2）四个终端的天线相对数量。为了实现保密性，我们提出了一种方案，其中发射机以利用 CIR 长度异质性的方式策略性地发送信息和人工噪声符号的混合。此外，协作干扰器以完全屏蔽在窃听节点接收到的所有信息符号的方式发送人工噪声符号。根据所提出的方案，即使合法接收器处的天线数量少于窃听者处的天线数量，也可以实现正 SDoF。