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）是第五代以后无线网络中一种有前景的通信安全补充技术。然而，当前PLS研究常基于无限编码块长或窃听链路信道状态信息（CSI）完美已知的理想假设。本文采用新的安全度量——平均信息泄露（AIL），研究有限块长（FBL）传输的性能。我们评估了在未知窃听者瞬时CSI条件下，任意信令和衰落信道的精确与近似AIL，并通过使用人工噪声（AN）波束赋形的案例研究，深入分析了瑞利衰落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影响的多种见解。特别地，我们的结果表明，允许较小程度的AIL可能显著提升系统可靠性。为改善系统性能，我们通过非自适应和自适应设计策略，制定并解决了平均安全吞吐量（AST）优化问题。研究结果凸显了块长设计、AN功率分配及其权衡对AST影响的重要性。