  The 5th generation (5G) wireless access technology, known as new radio (NR),
will address a variety of usage scenarios from enhanced mobile broadband to
ultra-reliable low-latency communications to massive machine type
communications. Key technology features include ultra-lean transmission,
support for low latency, advanced antenna technologies, and spectrum
flexibility including operation in high frequency bands and inter-working
between high and low frequency bands. This article provides an overview of the
essentials of the state of the art in 5G wireless technology represented by the
3GPP NR technical specifications, with a focus on the physical layer. We
describe the fundamental concepts of 5G NR, explain in detail the design of
physical channels and reference signals, and share the various design
rationales influencing standardization.
