Recently, MIMO (multiple-input-multiple-output) physical layer secure transmission has attracted great attentions. However, current schemes cannot defend against the passive eavesdroppers with arbitrary number of antennas. To address this problem, in this work, we propose a practical physical layer MIMO secure communication scheme (PLSC) to defend against such an eavesdropper with arbitrary number of antennas. In the proposed scheme, the transmitter first independently generates a random binary sequence as the “key bits (KB)” to “encrypt” (XOR) the confidential information. After that, the transmitter sends the “encrypted information” over the wireless channel, along with mapping key bits to the legitimate receiver simultaneously. The key principle lies in that the KB information is coded in the indexes of the activated/non-activated antennas combination of the legitimate user. Then, the legitimate receiver first observes his/her activated antenna indexes to obtain the corresponding key bits. After that, he/she demodulates the “encrypted information” at the activated antennas, and finally “decrypts” (XOR) the confidential information by using the observed key bits. However, due to the uniqueness and independence of MIMO wireless channel, for any other eavesdroppers who suffer an independent channel from legitimate users, we prove that it cannot observe any information about KB from the received signals, regardless of how many antennas it has used. Consequently, without knowledge of KB, it cannot decrypt any information about the confidential information, too. The reliability and security of PLSC are theoretically demonstrated. The simulation and numerical results fully verified the validity and effectiveness of the proposed scheme.

中文翻译：

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物理层保护 MIMO 通信，防止窃听者使用任意数量的天线


近年来，MIMO（多输入多输出）物理层安全传输引起了人们的广泛关注。然而，当前的方案无法防御具有任意数量天线的被动窃听者。为了解决这个问题，在这项工作中，我们提出了一种实用的物理层 MIMO 安全通信方案（PLSC）来防御这种具有任意数量天线的窃听者。在所提出的方案中，发射机首先独立生成一个随机二进制序列作为“密钥位（KB）”来“加密”（XOR）机密信息。之后，发送器通过无线信道发送“加密信息”，同时将密钥比特映射到合法接收器。其关键原理在于将KB信息编码在合法用户激活/非激活天线组合的索引中。然后，合法接收者首先观察他/她激活的天线索引以获得相应的密钥比特。之后，他/她在激活的天线处解调“加密信息”，最后利用观察到的密钥位“解密”（XOR）机密信息。然而，由于MIMO无线信道的唯一性和独立性，对于任何其他遭受合法用户独立信道的窃听者来说，我们证明无论使用多少根天线，它都无法从接收到的信号中观察到任何有关KB的信息。因此，如果不了解 KB，它也无法解密有关机密信息的任何信息。从理论上论证了PLSC的可靠性和安全性。仿真和数值结果充分验证了所提方案的有效性和有效性。