Due to its high speed and low latency, D2D communication plays an important role in providing proximity data services in 5G systems, which may contain privacy sensitive data. Covert communication is useful to protect the privacy of user data against adversaries. In a D2D underlaying cellular network, an antenna array can be used at a base station (BS) to transmit artificial noise to confuse adversaries that try to detect D2D covert signals. Based on the numbers of antennas at BS, two covert schemes are presented in this work and their performances are evaluated in terms of D2D covert throughput, i.e., maximum achievable D2D data rate with the given covertness requirements. As only channel distribution information (CDI) of adversary links is known to the BS, the average minimum error probability (AMEP) is used as a metric to measure the covertness performance. In the proposed schemes, closed-form expressions of the minimum AMEP and achievable D2D data rate are derived. It is shown that the derivation of minimum AMEP can be simplified if either one or massive antennas are allocated for sending artificial noise. The analytical results are compared to Monte-Carlo simulation results to verify the feasibility of the proposed schemes. It is also revealed that covert throughput can be further improved by setting system parameters properly, e.g., the number of antennas at BS and artificial noise transmit power.

中文翻译：

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具有天线阵列辅助人工噪声传输的 D2D 底层蜂窝网络中的隐蔽通信

由于其高速和低延迟，D2D 通信在 5G 系统中提供邻近数据服务方面发挥着重要作用，其中可能包含隐私敏感数据。隐蔽通信有助于保护用户数据的隐私免受攻击者的侵害。在 D2D 底层蜂窝网络中，可以在基站 (BS) 使用天线阵列来传输人工噪声，以迷惑试图检测 D2D 隐蔽信号的对手。基于基站的天线数量，本文提出了两种隐蔽方案，并根据 D2D 隐蔽吞吐量评估了它们的性能，即在给定隐蔽性要求的情况下，最大可实现的 D2D 数据速率。由于 BS 只知道敌对链路的信道分布信息 (CDI)，平均最小错误概率（AMEP）被用作衡量隐蔽性能的指标。在所提出的方案中，导出了最小 AMEP 和可实现的 D2D 数据速率的封闭形式表达式。结果表明，如果分配一个或大量天线用于发送人工噪声，则可以简化最小AMEP的推导。将分析结果与蒙特卡罗模拟结果进行比较，以验证所提出方案的可行性。还揭示了通过适当设置系统参数，例如基站处的天线数量和人工噪声发射功率，可以进一步提高隐蔽吞吐量。结果表明，如果分配一个或大量天线用于发送人工噪声，则可以简化最小AMEP的推导。将分析结果与蒙特卡罗模拟结果进行比较，以验证所提出方案的可行性。还揭示了通过适当设置系统参数，例如基站处的天线数量和人工噪声发射功率，可以进一步提高隐蔽吞吐量。结果表明，如果分配一个或大量天线用于发送人工噪声，则可以简化最小AMEP的推导。将分析结果与蒙特卡罗模拟结果进行比较，以验证所提出方案的可行性。还揭示了通过适当设置系统参数，例如基站处的天线数量和人工噪声发射功率，可以进一步提高隐蔽吞吐量。