Abstract:

In the multipath channel scenario of passive eavesdropping， the EaVEsdropper （Eve） only performs passive eavesdropping without transmitting any radio signals. The transmitter （Alice） is unable to determine any information of Eve， which brings great challenges to the secure transmission of information. In order to guarantee the secure transmission of information， under the condition that Alice knew the Channel State Information （CSI） of the legitimate receiver （Bob） but not Eve’s CSI， a precoding scheme to guarantee the physical layer security of legitimate Bob was proposed， and the security performance of the system was improved by enhancing the quality of the received signals of Bob. Firstly， without considering Eve， the precoding scheme for the upper bound on the reachable channel capacity of Bob was given based on the known CSI of Bob. Stable security capacity was obtained by using the channel specificity between Alice-Bob and Alice-Eve links. Then， the accurate closed-form expression for Bob’s average Bit Error Rate （BER） was derived from Bob’s outage probability in a Rayleigh flat fading environment. Simulation experimental results show that the proposed scheme can ensure Bob’s channel capacity always better than Eve’s channel capacity without changing the complexity of the receiver. At the same time， the proposed scheme can effectively improve the BER performance of Bob under the condition that the BER performance of Eve is greatly suppressed. And the security capacity is always guaranteed even when the Eve’s location condition is better than that of Bob.

Key words: Channel State Information (CSI), multipath channel, physical layer, security capacity, precoding, Single Carrier-Frequency Domain Equalization (SC-FDE), eavesdropping

摘要：

在被动窃听的多径信道场景下，窃听者（EaVEsdropper，Eve）仅被动窃听，不发射任何无线电信号，发射端（Alice）无法确定Eve的任何信息，给信息的安全传输带来了极大挑战。为了保障信息的安全传输，在Alice已知合法接收者（Bob）的信道状态信息（CSI）但是未知Eve的CSI的情况下，提出一种保障Bob的物理层安全的预编码方案，通过提高Bob接收信号的质量来提高系统的安全性能。首先，在不考虑Eve的情况下，仅根据已知的Bob的CSI给出可达Bob信道容量上界的预编码方案；利用Alice-Bob和Alice-Eve链路之间的信道特异性获得稳定的安全容量；然后，在瑞利平坦衰落环境下，通过Bob的中断概率推导出Bob的平均误码率（BER）准确的闭合表达式。仿真实验结果表明，所提方案在不改变接收机复杂度的基础上，能够保证Bob的信道容量始终优于Eve的信道容量。同时，所提方案能够在Eve的BER性能受到较大抑制的条件下，有效改善Bob的BER性能，即使Eve位置条件优于Bob也能保证安全容量始终存在。

关键词: 信道状态信息, 多径信道, 物理层, 安全容量, 预编码, 单载波频域均衡, 窃听