  Increased density of wireless devices, ever growing demands for extremely
high data rate, and spectrum scarcity at microwave bands make the millimeter
wave (mmWave) frequencies an important player in future wireless networks.
However, mmWave communication systems exhibit severe attenuation, blockage,
deafness, and may need microwave networks for coordination and fall-back
support. To compensate for high attenuation, mmWave systems exploit highly
directional operation, which in turn substantially reduces the interference
footprint. The significant differences between mmWave networks and legacy
communication technologies challenge the classical design approaches,
especially at the medium access control (MAC) layer, which has received
comparatively less attention than PHY and propagation issues in the literature
so far. In this paper, the MAC layer design aspects of short range mmWave
networks are discussed. In particular, we explain why current mmWave standards
fail to fully exploit the potential advantages of short range mmWave
technology, and argue for the necessity of new collision-aware hybrid resource
allocation frameworks with on-demand control messages, the advantages of a
collision notification message, and the potential of multihop communication to
provide reliable mmWave connections.
