Supporting URLLC has become one of the major considerations in the design of 5G systems. In the literature, it has been shown that cooperative relaying is an efficient strategy to improve the reliability of transmissions, support higher rates, and lower latency. However, prior studies have demonstrated the performance advantages of relaying generally under the ideal assumption of communicating arbitrarily reliably at Shannon's channel capacity, which is not an accurate performance indicator for relaying in URLLC networks in which transmission is required to be completed within a strict time span and coding schemes with relatively short blocklengths need to be employed. In this article, we address the performance modeling and optimization of relaying-enabled URLLC networks. We first discuss the accurate performance modeling of relay-enabled 5G networks. In particular, we provide a comprehensive summary of the performance advantage of applying relaying in 5G URLLC transmissions in comparison to the case of direct transmission (without relaying). Both a noise-limited scenario and an interference- limited scenario are discussed. Then we present tools for performance optimization utilizing the knowledge of either perfect or average channel side information. Finally, we summarize the proposed optimization schemes and discuss potential future research directions.

中文翻译：

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5G 中支持中继的超可靠低延迟通信


支持URLLC已成为5G系统设计的主要考虑因素之一。文献表明，协作中继是提高传输可靠性、支持更高速率和更低延迟的有效策略。然而，先前的研究证明了中继的性能优势通常是在香农信道容量下任意可靠通信的理想假设下实现的，这对于要求在严格时间跨度内完成传输的 URLLC 网络中的中继来说并不是一个准确的性能指标。并且需要采用块长度相对较短的编码方案。在本文中，我们将讨论支持中继的 URLLC 网络的性能建模和优化。我们首先讨论支持中继的 5G 网络的准确性能建模。特别是，我们全面总结了在 5G URLLC 传输中应用中继与直接传输（无中继）的情况相比的性能优势。讨论了噪声受限场景和干扰受限场景。然后，我们提出利用完美或平均通道辅助信息的知识进行性能优化的工具。最后，我们总结了所提出的优化方案并讨论了未来潜在的研究方向。