Fluid antenna systems (FASs) offer genuine simplicity for communication network design by eliminating expensive hardware overhead and reducing the complexity of access protocol architectures. Through the discovery of significant spatial diversity within a compact antenna space, FASs enable the implementation of reconfigurable-antenna-based architectures. However, current state-of-the-art studies rarely investigate the impact of finite blocklength constraints on FAS-based designs, leaving a gap in both analytical modeling and the establishment of a solid, universally applicable performance metric for finite blocklength fluid antenna systems (FBL-FAS). In this work, we focus on the study of FBL-FAS and, more importantly, derive a block error rate (BLER) bound that serves as a general and practical performance benchmark across various FAS architectures. The proposed BLER bound is computable both with and without an explicit statistical model, meaning that the BLER performance can be characterized analytically or empirically under model-aware or model-free system scenarios. Moreover, when the statistical model is known, the analytical results derived from the proposed BLER bound exhibit strong alignment with the empirical findings, demonstrating the remarkable simplicity, accuracy, and universality of the proposed BLER bound.

翻译：流体天线系统（FAS）通过消除昂贵的硬件开销并降低接入协议架构的复杂性，为通信网络设计提供了真正的简洁性。通过在紧凑的天线空间内发现显著的空间分集，FAS使得基于可重构天线的架构得以实现。然而，当前最先进的研究很少探讨有限块长约束对基于FAS的设计的影响，这在有限块长流体天线系统（FBL-FAS）的分析建模和建立坚实、普遍适用的性能指标方面留下了空白。在本工作中，我们专注于研究FBL-FAS，更重要的是，推导出了一个块错误率（BLER）界，该界可作为各种FAS架构的通用且实用的性能基准。所提出的BLER界在有无显式统计模型的情况下均可计算，这意味着在模型感知或无模型的系统场景下，BLER性能可以通过分析或经验方法进行表征。此外，当统计模型已知时，从所提出的BLER界推导出的分析结果与经验发现高度一致，证明了所提出的BLER界具有显著的简洁性、准确性和普适性。