  In this work, we briefly outline the core 5G air interface improvements
introduced by the latest New Radio (NR) specifications, as well as elaborate on
the unique features of initial access in 5G NR with a particular emphasis on
millimeter-wave (mmWave) frequency range. The highly directional nature of 5G
mmWave cellular systems poses a variety of fundamental differences and research
problem formulations, and a holistic understanding of the key system design
principles behind the 5G NR is essential. Here, we condense the relevant
information collected from a wide diversity of 5G NR standardization documents
(based on 3GPP Release 15) to distill the essentials of directional access in
5G mmWave cellular, which becomes the foundation for any corresponding
system-level analysis.
