Low-latency communication plays an increasingly important role in delay-sensitive applications by ensuring the real-time information exchange. However, due to the constraint on the maximum instantaneous power, guaranteeing bounded latency is challenging. In this paper, we investigate the reliability-latency-rate tradeoff in low-latency communication systems with finite-blocklength coding (FBC). Specifically, we are interested in the fundamental tradeoff between error probability, delay-violation probability (DVP), and service rate. Based on the effective capacity (EC), we present the gain-conservation equations to characterize the reliability-latency-rate tradeoffs in low-latency communication systems. In particular, we investigate the low-latency transmissions over an additive white Gaussian noise (AWGN) channel and a Nakagami-$m$ fading channel. By defining the service rate gain, reliability gain, and real-time gain, we conduct an asymptotic analysis to reveal the fundamental reliability-latency-rate tradeoff of ultra-reliable and low-latency communications in the high signal-to-noise-ratio (SNR) regime. To analytically evaluate and optimize the quality-of-service-constrained throughput of low-latency communication systems adopting FBC, an EC-approximation method is conceived to derive the closed-form expression of that throughput. Our results may offer some insights into the efficient scheduling of low-latency wireless communications, in which statistical latency and reliability metrics are crucial.

翻译：低时延通信通过保障实时信息交换，在时延敏感型应用中扮演着日益重要的角色。然而，受限于最大瞬时功率约束，确保有界时延具有挑战性。本文研究采用有限块长编码的低时延通信系统中的可靠性-时延-速率权衡问题。具体而言，我们关注误码概率、时延违反概率与服务速率之间的基本权衡关系。基于有效容量理论，我们提出增益守恒方程以刻画低时延通信系统中的可靠性-时延-速率权衡特性。特别地，我们研究了加性高斯白噪声信道与Nakagami-$m$衰落信道上的低时延传输。通过定义服务速率增益、可靠性增益与实时性增益，我们进行渐近分析以揭示高信噪比区域下超高可靠低时延通信的基本可靠性-时延-速率权衡规律。为解析评估和优化采用有限块长编码的低时延通信系统在服务质量约束下的吞吐量，本文提出一种有效容量近似方法，推导出该吞吐量的闭式表达式。我们的研究结果可为统计时延与可靠性指标至关重要的低时延无线通信高效调度提供理论参考。