Terahertz (THz) communication is one of the most promising candidates to accommodate high-speed mobile data services. This paper proposes a secure hybrid automatic repeat request with incremental redundancy (HARQ-IR) aided THz communication scheme, where the transmission secrecy is ensured by confusing the eavesdropper with dummy messages. The connection and secrecy outage probabilities are then derived in closed-form. Besides, the tail behaviour of the connection outage probability in high signal-to-noise ratio (SNR) is examined by carrying out the asymptotic analysis, and the upper bound of the secrecy outage probability is obtained in a simple form by capitalizing on large deviations. With these results, we take a step further to investigate the secrecy long term average throughput (LTAT). By noticing that HARQ-IR not only improves the reliability of the legitimate user, but also increases the probability of being eavesdropped, a robust rate adaption policy is finally proposed to maximize the LTAT while restricting the connection and secrecy outage probabilities within satisfactory requirements.

翻译：太赫兹通信是支持高速移动数据服务最具前景的技术之一。本文提出一种安全混合自动重传请求-增量冗余（HARQ-IR）辅助太赫兹通信方案，通过向窃听者发送虚假消息确保传输安全性。推导出连通中断概率与安全中断概率的闭合表达式，并基于高信噪比渐近分析揭示连通中断概率的尾部特性，同时利用大偏差理论获得安全中断概率的简化上界。在现有成果基础上，进一步研究安全长期平均吞吐量（LTAT）。鉴于HARQ-IR在提升合法用户可靠性的同时会增大被窃听风险，最终提出一种鲁棒速率自适应策略，在满足连通中断概率与安全中断概率约束下最大化LTAT。