  Besides enabling an enhanced mobile broadband, next generation of mobile
networks (5G) are envisioned for the support of massive connectivity of
heterogeneous Internet of Things (IoT)s. These IoTs are envisioned for a large
number of use-cases including smart cities, environment monitoring, smart
vehicles, etc. Unfortunately, most IoTs have very limited computing and storage
capabilities and need cloud services. Hence, connecting these devices through
5G systems requires huge spectrum resources in addition to handling the massive
connectivity and improved security. This article discusses the challenges
facing the support of IoTs through 5G systems. The focus is devoted to
discussing physical layer limitations in terms of spectrum resources and radio
access channel connectivity. We show how sparsity can be exploited for
addressing these challenges especially in terms of enabling wideband spectrum
management and handling the connectivity by exploiting device-to-device
communications and edge-cloud. Moreover, we identify major open problems and
research directions that need to be explored towards enabling the support of
massive heterogeneous IoTs through 5G systems.
