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.
I. INTRODUCTIONThe foreseen success of the Internet of Things (IoT) and its applications is the result of three major trends. First, fifth-generation (5G) systems have promises for meeting stringent QoS requirements that legacy systems fail to meet. Examples of such requirements are high data rates, low energy consumption, low latency, high capacity, and improved security. These expected improvements make 5G an ideal candidate for ensuring required connectivity and services for massive and heterogenous IoT devices [1]. The second trend is the emergence of cloud computing services, which are believed to play a vital role in making IoT a success by enabling diverse IoT services and applications that were not possible before. Bringing computing and storage resources closer to the IoT devices by means of edge computing has great promises for lowering energy consumption by releasing the devices from the burden of having to deal with some or most of the computation and energy needed for task execution [2]. The third trend is the adoption of device-to-device (D2D) communications envisioned for public safety with the potential for enabling more decentralized network management and local traffic offloading [3]. D2D offers 5G real-time assurances and better spectrum and resource allocation efficiency [3]. These (technological) trends have jointly led to a common belief that the success of IoT applications is rather a possible reality.