Physical-layer security (PLS) is a promising technique to complement communication security in beyond-5G wireless networks. However, PLS developments in current research are often based on the ideal assumption of infinite coding blocklengths or perfect knowledge of the wiretap link's channel state information (CSI). In this work, we study the performance of finite blocklength (FBL) transmissions using a new secrecy metric - the average information leakage (AIL). We evaluate the exact and approximate AIL with arbitrary signaling and fading channels, assuming that the eavesdropper's instantaneous CSI is unknown. We then conduct case studies that use artificial noise (AN) beamforming to thoroughly analyze the AIL in both Rayleigh and Rician fading channels. The accuracy of the analytical expressions is verified through extensive simulations, and various insights regarding the impact of key system parameters on the AIL are obtained. Particularly, our results reveal that allowing a small level of AIL can potentially lead to significant reliability improvements. To improve the system performance, we formulate and solve an average secrecy throughput (AST) optimization problem via both non-adaptive and adaptive design strategies. Our findings highlight the significance of blocklength design and AN power allocation, as well as the impact of their trade-off on the AST.

翻译：物理层安全（PLS）是增强超5G无线网络通信安全的一项有前景的技术。然而，当前研究中的PLS发展常基于无限编码块长或完美已知窃听链路信道状态信息（CSI）的理想假设。本文采用一种新的保密度量——平均信息泄漏（AIL），研究有限块长（FBL）传输的性能。我们评估了在窃听者瞬时CSI未知条件下，采用任意信号和衰落信道的精确与近似AIL。随后，通过使用人工噪声（AN）波束成形的案例研究，深入分析了瑞利和莱斯衰落信道中的AIL。通过大量仿真验证了解析表达式的准确性，并获得了关于关键系统参数对AIL影响的多方面见解。特别地，我们的结果表明，允许较小程度的AIL可能显著提升可靠性。为改善系统性能，我们通过非自适应与自适应设计策略，制定并求解了平均保密吞吐量（AST）优化问题。研究结果突显了块长设计与AN功率分配的重要性，以及两者权衡对AST的影响。