Since the advent of ultra-reliable and low-latency communications (URLLC), the requirements of low-latency applications tend to be completely characterized by a single pre-defined latency-reliability target. That is, operation is optimal whenever the pre-defined latency threshold is met but the system is assumed to be in error when the latency threshold is violated. This vision is severely limited and does not capture the real requirements of most applications, where multiple latency thresholds can be defined, together with incentives or rewards associated with meeting each of them. Such formulation is a generalization of the single-threshold case popularized by URLLC and, in the asymptotic case, approximates to defining a cost for each point in the support of the latency distribution. In this paper, we explore the implications of defining multiple latency targets on the design of access protocols and on the optimization of repetition-based access strategies in orthogonal and non-orthogonal multiple access scenarios with users that present heterogeneous traffic characteristics and requirements. We observe that the access strategies of the users can be effectively adapted to the requirements of the application by carefully defining the latency targets and the associated rewards.

翻译：自超可靠低延迟通信（URLLC）问世以来，低延迟应用的需求往往完全由单个预定义的延迟-可靠性目标来表征。即，只要满足预定义的延迟阈值，系统即处于最优运行状态，而一旦违反延迟阈值则被视为系统错误。这一视角存在严重局限，未能捕捉大多数应用的实际需求——这些应用可定义多个延迟阈值，并为达成每个阈值设置相应的激励或奖励机制。此类表述是URLLC推广的单阈值场景的泛化形式，在渐进情况下近似于为延迟分布支撑集上的每个点定义代价函数。本文探究了在具有异构流量特征与需求用户的正交/非正交多址接入场景中，定义多个延迟目标对接入协议设计及基于重复的接入策略优化的影响。研究表明，通过精细定义延迟目标及其关联奖励，可有效调整用户的接入策略以适应应用需求。