High-speed, low latency, and heterogeneity features of 5G, as the common denominator of many emerging and classic wireless applications, have put wireless technology back in the spotlight. Continuous connectivity requirement in low-power and wide-reach networks underlines the need for more efficient routing over scarce wireless resources, in multi-hp scenarios. In this regard, Opportunistic Routing (OR), which utilizes the broadcast nature of wireless media to provide transmission cooperation amongst a selected number of overhearing nodes, has become more promising than ever. Crucial to the overall network performance, which nodes to participate and where they stand on the transmission-priority hierarchy, are decided by user-defined OR metrics embedded in OR protocols. Therefore, the task of choosing or designing an appropriate OR metric is a critical one. The numerousness, proprietary notations, and the objective variousness of OR metrics can cause the interested researcher to lose insight and become overwhelmed, making the metric selection or design effort-intensive. While there are not any comprehensive OR metrics surveys in the literature, those who partially address the subject are non-exhaustive and lacking in detail. Furthermore, they offer limited insight regarding related taxonomy and future research recommendations. In this paper, starting with a custom tutorial with a new look to OR and OR metrics, we devise a new framework for OR metric design. Introducing a new taxonomy enables us to take a structured, investigative, and comparative approach to OR metrics, supported by extensive simulations. Exhaustive coverage of OR metrics, formulated in a unified notation, is presented with sufficient details. Self-explanatory, easy-to-grasp, and visual-friendly quick references are provided, which can be used independently from the rest of the paper. Finally, a new insightful framework for future research directions is developed. This tutorial-survey has been organized to benefit both generalists and OR specialists equally, and to be used not only in its entirety but selectively as well.

作为许多新兴和经典无线应用的共同点，5G的高速，低延迟和异构特性使无线技术重新成为人们关注的焦点。低功率和范围广泛的网络中对持续连接的要求强调了在多马力的情况下，需要在稀缺的无线资源上进行更高效路由的需求。在这方面，利用无线媒体的广播特性在选定数量的监听节点之间提供传输协作的机会路由（OR）比以往任何时候都更有希望。对于整个网络性能而言，至关重要的是要参与的节点以及它们在传输优先级层次结构上的位置，这取决于嵌入在OR协议中的用户定义的OR指标。因此，选择或设计适当的OR指标的任务非常关键。OR指标的众多性，专有符号和客观的多样性会导致感兴趣的研究人员失去见识并变得不知所措，从而导致指标选择或设计工作量很大。尽管文献中没有进行任何全面的OR指标调查，但部分解决该主题的人并不详尽，并且缺乏详细信息。此外，他们对相关分类法和未来研究建议的见解有限。在本文中，我们从一个定制的教程开始，对OR和OR度量有了新的外观，我们设计了一个新的OR度量设计框架。引入新的分类法使我们能够采用结构化，研究性和比较性的OR指标方法，并得到大量模拟的支持。以统一的符号表示的OR指标的详尽介绍，包含足够的详细信息。提供了不言自明，易于掌握和视觉友好的快速参考，可以独立于本文的其余部分使用。最后，为未来的研究方向开发了一个新的有见地的框架。本教程调查的组织目的是使通才和OR专家均能从中受益，并且不仅可以整体使用，还可以有选择地使用。