In a wiretap channel, due to the passive nature of eavesdropper and the inevitable errors during channel estimation or feedback, the channel state information is usually imperfectly known at the transmitter. While probabilistic constrained secure transmission provides an elegant formulation to tackle these uncertainties, current works mostly focus on the fixed-rate secure transmission design. To exploit the dynamic channel state information for performance enhancement, this paper investigates a variable-rate transmission scheme with adjustable rate and power, under the outage probabilistic constraints and upper bounding rate constraint. By leveraging the first-order and log-concavity properties of the Marcum Q-function, closed-form optimal secure transmission design is obtained. Furthermore, the optimality of the proposed method empowers us to concisely quantify the performance gain brought by rate variation. Numerical results show that the proposed scheme achieves significantly lower average outage probability and higher throughput than the fixed-rate scheme no matter with or without upper bound rate limitation.

中文翻译：

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概率约束安全传输：可变速率设计和性能分析


在窃听信道中，由于窃听者的被动性质以及信道估计或反馈过程中不可避免的错误，信道状态信息通常在发送端并不完全已知。虽然概率约束安全传输提供了一种优雅的公式来解决这些不确定性，但当前的工作主要集中在固定速率安全传输设计上。为了利用动态信道状态信息来增强性能，本文研究了在中断概率约束和上限速率约束下具有可调节速率和功率的可变速率传输方案。通过利用 Marcum Q 函数的一阶和对数凹性特性，获得了闭式最优安全传输设计。此外，所提出方法的最优性使我们能够简明地量化速率变化带来的性能增益。数值结果表明，无论是否有上限速率限制，该方案都比固定速率方案实现了显着更低的平均中断概率和更高的吞吐量。