How to provide information security while fulfilling ultra reliability and low-latency requirements is one of the major concerns for enabling the next generation of ultra-reliable and low-latency communications service (xURLLC), specially in machine-type communications. In this work, we investigate the reliability-security tradeoff via defining the leakage-failure probability, which is a metric that jointly characterizes both reliability and security performances for short-packet transmissions. We discover that the system performance can be enhanced by counter-intuitively allocating fewer resources for the transmission with finite blocklength (FBL) codes. In order to solve the corresponding optimization problem for the joint resource allocation, we propose an optimization framework, that leverages lower-bounded approximations for the decoding error probability in the FBL regime. We characterize the convexity of the reformulated problem and establish an efficient iterative searching method, the convergence of which is guaranteed. To show the extendability of the framework, we further discuss the blocklength allocation schemes with practical requirements of reliable-secure performance, as well as the transmissions with the statistical channel state information (CSI). Numerical results verify the accuracy of the proposed approach and demonstrate the reliability-security tradeoff under various setups.

翻译：如何在满足超可靠低延迟需求的同时提供信息安全，是推动下一代超可靠低延迟通信服务（xURLLC）的关键挑战之一，特别是在机器类通信场景中。本研究通过定义泄漏失败概率，这一联合表征短包传输可靠性与安全性能的指标，探讨了可靠性-安全性权衡。我们发现，通过反直觉地分配更少的资源用于有限块长编码传输，能够提升系统性能。为解决资源联合优化问题，我们提出了一种优化框架，利用有限块长机制下译码错误概率的下界近似。我们刻画了重构问题的凸性，并建立了一种收敛性有保证的高效迭代搜索方法。为展示框架的可扩展性，进一步讨论了具有可靠-安全性能实际约束的块长分配方案，以及基于统计信道状态信息的传输方案。数值结果验证了所提方法的准确性，并展示了不同配置下的可靠性-安全性权衡关系。