This paper originates from a panel with the above title, held at IEEE VTC Spring 2009, in which the authors took part. The enthusiastic response it received prompted us to discuss for a wider audience whether research at the physical layer (PHY) is still relevant to the field of wireless communications. Using cellular systems as the axis of our exposition, we exemplify areas where PHY research has indeed hit a performance wall and where any improvements are expected to be marginal. We then discuss whether the research directions taken in the past have always been the right choice and how lessons learned could influence future policy decisions. Several of the raised issues are subsequently discussed in greater details, e.g., the growing divergence between academia and industry. With this argumentation at hand, we identify areas that are either underdeveloped or likely to be of impact in coming years -hence corroborating the relevance and importance of PHY research.
IntroductionWireless communication has been the subject of much hype: branded with terms like ubiquitous, pervasive, fundamental, paradigm-shifting, and revolutionary. Cellular communication systems have been the focus of this Broadway play, with the physical layer (PHY) taking the leading role. After decades of thriving advances and exciting developments such as OFDM, turbo codes, LDPC codes, or MIMO, cellular communication systems are becoming mature. Doubts about the viability and relevance of PHY research have naturally arisen, leading to a growing sense that the work in this area is generating diminishing returns and that the discipline may be essentially dead. But is it? Doubts about the likelihood of great advances in a particular field are frequently expressed in scientific communities and, in fact, they may spur healthy debates; [Smo06], for instance, discusses the negative impact that the hype on string theory had on how funding was distributed within physics communities. Actually, doubts have been cast on research within the PHY before. For example, in a 1971 workshop on coding theory, Ned Weldon famously declared: "coding is dead" [Luc93]. In hindsight, of course, coding was not dead and a number of breakthroughs were still to come.
