Abstract-Due to spectrum scarcity in microwave bands used by legacy communication technologies, millimeter wave (mmWave) bands are considered as a promising enabler for 5G cellular networks to provide multi-gigabit wireless access. However, mmWave communications exhibit high attenuations, vulnerability to obstacles, and sparse-scattering environments, which are not taken into account in the existing cellular wireless design approaches. Moreover, the small wavelengths of mmWave signals make it possible to incorporate a large number of antenna elements both at the base stations and at the user equipments, which in turn lead to high directivity gains and fullydirectional communications. This level of directionality can result in a network that is noise-limited as opposed to interferencelimited. The significant differences between mmWave networks and traditional ones challenge the classical design constraints, objectives, and available degrees of freedom. This demands a reconsideration of almost all design aspects in mmWave systems, where, despite a recent wave of investigations at the physical layer, very little can be found for the medium access control (MAC) layer. This paper aims at filling this important research gap. The purpose of this study is both to survey the state-ofthe-art and to discuss the challenges that arise at the MAC layer of mmWave cellular systems and to propose original research directions to address those challenges. Specifically, this paper focuses on the main MAC decisions such as synchronization, random access, handover, channelization, interference management, scheduling, and association. New challenges and new tradeoffs are identified, and solution approaches based on special characteristics of mmWave systems are suggested. It is concluded that fully-directional communication when supported with proper MAC layer design is an essential component of mmWave cellular networks.
MAC tier issues, such as synchronization, random access, handover, channelization, interference management, scheduling, and association for mmWave frequency band are discussed by Hossein Shokri-Ghadikola et al. REF .
Millimeter Wave Cellular Networks: A MAC Layer Perspective
IEEE Transactions on Communications
IEEE Transactions on Communications
Computer Science Mathematics