In this paper, we propose the use of data and energy buffering in wireless powered relays, while we also design scheduling schemes, with the aim to increase the secrecy throughput. More specifically, it is assumed that Alice transmits information to Bob by using half-duplex randomize-and-forward relaying with simultaneous wireless information and power transfer, under the existence of a passive eavesdropper. First, considering a conventional system, i.e., without energy and data buffering, an optimal baseline policy is designed. Then, focusing on buffer-aided relaying, we maximize the average secrecy throughput under the stability requirement for data and energy queues by using the framework of Lyapunov optimization, according to which, we transform the initial stochastic optimization problem into a sequence of online subproblems. The proposed online adaptive transmission policy dynamically allocates the available resources, i.e., time and power, with respect to the channel state information, as well as the states of the buffers. In addition, our analysis reveals the existence of an interesting trade-off between the average secrecy throughput and the average queue delay. Simulation results validate the analysis and demonstrate that the proposed buffer-aided scheme significantly improves the average secrecy throughput compared to the baseline one.

中文翻译：

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带 SWIPT 的缓冲区辅助安全中继网络

在本文中，我们建议在无线供电中继中使用数据和能量缓冲，同时我们还设计了调度方案，旨在提高保密吞吐量。更具体地说，假设 Alice 在存在被动窃听者的情况下，通过使用半双工随机转发中继，同时进行无线信息和功率传输，将信息传输给 Bob。首先，考虑传统系统，即没有能量和数据缓冲，设计最优基线策略。然后，针对缓冲区辅助中继，我们利用李雅普诺夫优化的框架在数据和能量队列的稳定性要求下最大化平均保密吞吐量，根据该框架，我们将初始随机优化问题转化为一系列在线子问题。所提出的在线自适应传输策略相对于信道状态信息以及缓冲器的状态动态地分配可用资源，即时间和功率。此外，我们的分析揭示了平均保密吞吐量和平均队列延迟之间存在一个有趣的权衡。仿真结果验证了分析，并表明与基线方案相比，所提出的缓冲辅助方案显着提高了平均保密吞吐量。