Millimeter-Wave Meets D2D: A Survey

Device-to-device (D2D) and millimeter-wave (mmW) communications play an important role in the design of future wireless communication systems since they are mature and resource-efficient technologies. Integrating both technologies while retaining the benefit they offer in isolation is challenging. In this article, we review the literature on mmW-based D2D proposals to enable network applications and service extensions that span from network-controlled use cases to opportunistic solutions for direct data exchange, caching, and relay. The survey unveils that, although a large effort has been devoted to the study of D2D with mmW, we are still far from a full analytical and experimental characterization of the system. More effort is needed in view of 5G and beyond, to consider the integration of network computing elements and to protect mmW-based D2D against security threats.