Sixth generation promises to have a variety of applications, as well as network entities, in terms of power, range, data rates, latency, and propagation environment. The overall heterogeneity of the network poses significant challenges in terms of physical (PHY) layer design. This article first identifies some of the areas where the 5G multinumerology orthogonal frequency division multiplexing (OFDM) falls short before discussing the possible approaches toward PHY design. In particular, we discuss a backward-compatible, forward-looking, and extendable PHY layer framework that can be extended as new requirements arise to enable a graceful and sustainable network evolution. This is illustrated with a simple case study, where users with different requirements are allowed to use the same time-frequency (T-F) resources in a cohesive manner. The article concludes with the discussion of some critical research problems/areas pertaining to the said framework.

中文翻译：

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正交频分复用：6G 物理层设计的前进方向？

第六代有望在功率、范围、数据速率、延迟和传播环境方面拥有各种应用程序和网络实体。网络的整体异构性给物理（PHY）层设计带来了重大挑战。本文首先确定了 5G 多参数正交频分复用 (OFDM) 的一些不足之处，然后再讨论 PHY 设计的可能方法。特别是，我们讨论了向后兼容、前瞻性和可扩展的 PHY 层框架，该框架可以随着新需求的出现而进行扩展，以实现优雅且可持续的网络演进。这是通过一个简单的案例研究来说明的，其中允许具有不同需求的用户以凝聚的方式使用相同的时频（TF）资源。本文最后讨论了与上述框架相关的一些关键研究问题/领域。