5G Network Architecture
This paper was published in 2018 within the Journal of the Institute of Telecommunications Professionals (Volume 12, Part 1, Pages 9-15) and is made available here with their kind permission.
The 20th December 2017 will be remembered as an important day in telecommunications history as, on this day, during a meeting in Lisbon, Portugal, 3GPP (3rd Generation Partnership Project) successfully completed the first implementable 5G NR specification. NR (New Radio) is the term used to describe the 5G air interface and radio access network. This is the first phase of delivering a complete 5G end-to-end network based on the architecture presented in this article.
The first mobile implementation of 5G is designed to work in Non-Standalone (NSA) mode to support the enhanced Mobile Broadband (eMBB) use case. In NSA mode the connection is anchored in Long Term Evolution (LTE) (3GPP 4G technology) with 5G NR carriers being used to increase data rate and reduce latency.
5G is often referred to as the next generation of mobile communications technology but the potential is more significant than this. 5G will likely become the future of communications, supporting fixed and mobile access. In addition to eMBB, 5G will support Ultra-Reliable and Low Latency Communications (URLLC), also referred to as Mission Critical Communications, and massive Machine Type Communications (mMTC) – an evolution of IoT – along with Fixed and Mobile Convergence. Although the diverse requirements of eMBB, URLLC and mMTC will not be supported from day-one, a flexible approach to the design of NR has been necessary to ensure 5G standards will evolve to meet all requirements. This approach has resulted in a NR design with scalable numerology (numerology refers to waveform parametrisation, e.g. cyclic prefix and subcarrier spacing in Orthogonal Frequency Division Multiplexing (OFDM)), numerology multiplexing and implementation of Time Division Duplex (TDD). TDD is better suited to data-centric services in which the downlink (the connection from network to user) will carry significantly more data traffic than the uplink (connection from user to network) in the vast majority of use cases. TDD will be the most common implementation across the majority of initial 5G frequency bands although it should be noted that Frequency Division Duplex (FDD) operation is also supported.
The December 2017 release of 5G NR does not include a 5G Next Generation Core (NGC) network but rather relies on an evolution of the existing 4G Evolved Packet Core (EPC) often referred to as EPC+. This means that a 5G-capable device will be connected to an enhanced 3GPP Release 15 4G radio for control plane and 4G and/or 5G radio for user plane traffic flows.