Orthogonal frequency division multiplexing: The Way Forward for 6G Physical Layer Design?

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.