Emerging applications such as wireless industrial control or vehicular communications pose strict requirements in terms of latency and reliability on wireless communication systems. Since contemporary communication standards are not able to fulfill all of these requirements, reliable low-latency communication is an important research topic. Using multiple communication paths at once, i.e., multi-connectivity (MC), is a promising approach to get closer to reaching this goal of reliable low-latency communication. In this survey we provide a definition for MC, identify main scheduling categories, compare different network architectures and consider different layers for implementing MC. We provide an overview of MC methods already established in IEEE and 3GPP standardization and discuss recent MC approaches on a layer-by-layer basis. Moreover, we reflect on the existing literature and identify open issues. We suggest further research directions such as the OSI Layer where separation and aggregation of the different paths for MC is performed, the characteristics of the paths to be used for MC and dynamic scheduling techniques for MC settings.

中文翻译：

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多连接作为可靠低延迟通信的促成因素 - 概述

无线工业控制或车载通信等新兴应用对无线通信系统的延迟和可靠性提出了严格的要求。由于当代通信标准无法满足所有这些要求，可靠的低延迟通信是一个重要的研究课题。一次使用多条通信路径，即多连接 (MC)，是接近实现可靠低延迟通信这一目标的有前途的方法。在本次调查中，我们提供了 MC 的定义，确定了主要的调度类别，比较了不同的网络架构并考虑了实现 MC 的不同层。我们概述了 IEEE 和 3GPP 标准化中已经建立的 MC 方法，并逐层讨论了最近的 MC 方法。而且，我们反思现有文献并确定未解决的问题。我们建议进一步的研究方向，例如执行 MC 的不同路径的分离和聚合的 OSI 层、用于 MC 的路径的特性以及用于 MC 设置的动态调度技术。