The 5G New Radio interface

5G networks are aiming for throughputs of a few Gbit/s and latencies in the millisecond range, as well as a high capacity in Gbit/s per cell, while limiting energy consumption. These objectives require changes to the radio interface of 5G networks compared with that of 4G networks. The choice was made to retain the same principles of radio access network architecture, and to keep transmission on orthogonal subcarriers or Orthogonal Frequency Division Multiplexing (OFDM) to facilitate the transition from 4G to 5G. On the other hand, there are many more possible settings in both the frequency and time domains. An important feature of the 5G-NR radio interface is that it is designed to enable the use of antenna arrays that can be used both to concentrate radiation in the direction of interest (beamforming) and to enable transmissions of different streams over the same time-frequency resource, the principle of Multiple-Input-Multiple-Output (MIMO) techniques.

The aim of this article is to set out the key principles of the 5G radio interface, known as New Radio (NR), and to show how the choices made enable the desired objectives to be achieved. After presenting the physical and protocol architecture, it reviews the general principles of transmission and allocation, and introduces multi-antenna technologies. He discusses frequency organization, allowing us to deduce the order of magnitude of achievable data rates in different frequency ranges, and then temporal organization to highlight the influence on latency. It explains how the beacon channel is organized to reduce energy consumption and allow beam-forming, and how access mechanisms are consistent with this organization. It concludes with a presentation of the control functions on an established radio link, and in particular the main reference signals inserted in the transmission, which are essential for this control.