Cooperative wireless networks have been facing security challenges due to the inherent openness of wireless channels. Previous studies on the physical layer security (PLS) of cooperative networks mainly focus on scenarios with only trusted relays. In practice, however, untrusted relays may exist in the network and such relays may refuse to cooperate or even work as a helper of an eavesdropper for packets eavesdropping/interception. To address this issue, we consider in this paper a cooperative wireless network with untrusted relays and a passive eavesdropper attempting to wiretap packets transmitted in the network. To select a secure and trusted relay, we first propose two buffer-aided relay selection schemes, one for perfect eavesdropper channel state information (CSI) case and another for no eavesdropper CSI case. We then conduct theoretical analysis to derive the models for the performance metrics of secrecy outage probability (SOP) and expected queuing delay. Finally, simulation and numerical results are provided for the validation of our theoretical models. The results indicate that our proposed schemes can outperform the typical max-ratio scheme under perfect eavesdropper CSI case and can outperform the max-link and the max-max relay selection schemes under no eavesdropper CSI case in terms of the SOP and expected queuing delay.

由于无线信道固有的开放性，协作无线网络一直面临安全挑战。先前对协作网络物理层安全（PLS）的研究主要集中在只有可信中继的场景。然而，在实践中，网络中可能存在不受信任的中继，这些中继可能拒绝合作，甚至充当窃听者的助手来窃听/拦截数据包。为了解决这个问题，我们在本文中考虑了一个协作无线网络，它具有不受信任的中继和一个试图窃听网络中传输的数据包的被动窃听者。为了选择安全可信的中继，我们首先提出了两种缓冲辅助中继选择方案，一种用于完美窃听者信道状态信息（CSI）情况，另一种用于无窃听者 CSI 情况。然后，我们进行理论分析以推导出保密中断概率 (SOP) 和预期排队延迟的性能指标模型。最后，提供了模拟和数值结果以验证我们的理论模型。结果表明，我们提出的方案在完美窃听者 CSI 情况下优于典型的最大比率方案，并且在 SOP 和预期排队延迟方面优于无窃听者 CSI 情况下的最大链路和最大最大中继选择方案。