5G NR (New Radio) is a new radio access technology (RAT) developed by 3GPP for the 5G (fifth generation) mobile network. It was designed to be the global standard for the air interface of 5G networks.
The study of NR within 3GPP started in 2015, and the first specification was made available by the end of 2017. While the 3GPP standardization process was ongoing, the industry had already begun efforts to implement infrastructure compliant with the draft standard, with the first large-scale commercial launch of 5G NR having occurred in the end of 2018. Since 2019, many operators have deployed 5G NR networks and handset manufacturers have developed 5G NR enabled handsets.
5G NR uses frequency bands in two frequency ranges:
In 2018, 3GPP published Release 15, which includes what is described as "Phase 1" standardization for 5G NR. The timeline for Release 16, which will be "5G phase 2", follows a freeze date of March 2020 and a completion date of June 2020, Release 17 was originally scheduled for delivery in September 2021. but, because of the COVID-19 pandemic, it was rescheduled for June 2022.
Initial 5G NR launches will depend on existing 4G LTE infrastructure in non-standalone (NSA) mode, before maturation of the standalone (SA) mode with the 5G core network. Additionally, the spectrum can be dynamically shared between 4G LTE and 5G NR.
The non-standalone (NSA) mode of 5G NR refers to an option of 5G NR deployment that depends on the control plane of an existing 4G LTE network for control functions, while 5G NR is exclusively focused on the user plane. This is reported to speed up 5G adoption, however some operators and vendors have criticized prioritizing the introduction of 5G NR NSA on the grounds that it could hinder the implementation of the standalone mode of the network.
To make better use of existing assets, carriers may opt to dynamically share it between 4G LTE and 5G NR. The spectrum is multiplexed over time between both generations of mobile networks, while still using the 4G LTE network for control functions, depending on user demand. Dynamic spectrum sharing (DSS) may be deployed on existing 4G LTE equipment as long as it is compatible with 5G NR. Only the 5G NR terminal needs to be compatible with DSS.
The standalone (SA) mode of 5G NR refers to using 5G cells for both signalling and information transfer. It includes the new 5G Packet Core architecture instead of relying on the 4G Evolved Packet Core, to allow the deployment of 5G without the LTE network. It is expected to have lower cost, better efficiency, and to assist development of new use cases.
5G NR supports five subcarrier spacings:
|Sub-Carrier Spacing (kHz)||Slot duration (ms)||Frequency Bands||Notes|
|15||1||FR1||Same as LTE|
|60||0.25||FR1 and FR2||Both normal Cyclic Prefix (CP) and extended CP may be used with 60 kHz subcarrier spacing|
|120||0.125||FR2||This is the highest subcarrier spacing for the path of data|
|240||0.0625||FR2||This is only possible for search and measurement purposes, using the Synchronization Signal Block (SSB)|
The length of CP is inversely proportional to the subcarrier spacing. It is 4.7 μs with 15 kHz, and 4.7 / 16 = 0.29 μs for 240 kHz subcarrier spacing.