Low-latency communication plays an increasingly important role in delay-sensitive applications by ensuring the real-time exchange of information. However, due to the constraints on the maximum instantaneous power, bounded latency is hard to be guaranteed. In this paper, we investigate the reliability-latency-rate tradeoff in low-latency communications with finite-blocklength coding (FBC). More specifically, we are interested in the fundamental tradeoff between error probability, delay-violation probability (DVP), and service rate. Based on the effective capacity (EC) and normal approximation, we present several gain-conservation inequalities to bound the reliability-latency-rate tradeoffs. In particular, we investigate the low-latency transmissions over an additive white Gaussian noise (AWGN) channel, over a Rayleigh fading channel, with frequency or spatial diversity, and over a Nakagami-$m$ fading channel. To analytically evaluate the quality-of-service-constrained low-latency communications with FBC, an EC-approximation method is further conceived to derive the closed-form expression of quality-of-service-constrained throughput. For delay-sensitive transmissions in which the latency threshold is greater than the channel coherence time, we find an asymptotic form of the tradeoff between the error probability and DVP over the AWGN and Rayleigh fading channels. Our results may provide some insights into the efficient scheduling of low-latency wireless communications in which statistical latency and reliability metrics are adopted.

翻译：低延迟通信通过确保信息的实时交换，在时延敏感应用中发挥着日益重要的作用。然而，由于最大瞬时功率的限制，有界延迟难以得到保证。本文研究了基于有限块长编码（FBC）的低延迟通信中的可靠性-延迟-速率权衡。具体而言，我们关注错误概率、延迟违反概率（DVP）与服务速率之间的基本权衡关系。基于有效容量（EC）和正态近似，我们提出了若干增益守恒不等式来约束可靠性-延迟-速率权衡。特别地，我们研究了加性高斯白噪声（AWGN）信道、瑞利衰落信道、频率或空间分集以及Nakagami-$m$衰落信道上的低延迟传输。为了分析评估采用FBC的服务质量约束低延迟通信，进一步提出了一种EC近似方法，用于推导服务质量约束吞吐量的闭式表达式。对于延迟门限大于信道相干时间的时延敏感传输，我们发现了AWGN和瑞利衰落信道上错误概率与DVP权衡的渐近形式。我们的研究结果可为采用统计延迟和可靠性指标的低延迟无线通信的高效调度提供理论依据。