5G Network Architecture

With 3GPP completing the first implementable 5G New Radio (NR) specification in December 2017 comes the first phase of delivering a complete 5G end-to-end network.

By June 2018 3GPP will have completed standardisation of the 5G network architecture, including the Next Generation Core (NGC) enabling the full feature set of 5G to be supported. 5G is more than just the next generation of mobile; it will likely become the future of communications, supporting fixed and mobile access and take us forward into an era of high reliability, low latency, Internet of Things, massive machine Type Communications and so on.

Three pioneer frequency bands have been earmarked for the introduction of 5G services in Europe:

  • 700mHz to provide a wide-area coverage layer.
  • 3.4 to 3.8GHz to provide a large amount of contiguous spectrum for high data rates and low-latency services, and also a capacity solution in congested areas. The probable early deployment in this band will require support from lower frequency bands to extend the range of the uplink to match the achievable downlink. The initial enhanced uplink support is likely to come from LTE via a
    feature known as dual-connectivity.
  • 24.25 to 27.5GHz to provide extremely high-speed data services and very low latency at short distances along with addressing future massive area capacity density requirements.

The 3.4 to 3.6GHz band has a high propagation loss and will not necessarily offer contiguous coverage for both downlink and uplink. Therefore, the wider coverage of LTE, typically at 800mHz or 1800mHz, will support the control plane and, in some scenarios, the user plane.

One advantage of 5G is the adoption of massive multiple Input, multiple Output technology with 64 radio transceivers and antennas within the antenna module in
such a way that beam-forming can be implemented to enhance the coverage by
increased directional antenna gain.

While the current focus of 5G spectrum discussions are on new spectrum, existing cellular frequency bands are eventually expected to be re-farmed to 5G NR.

Prior to the availability of the NGC, 5G will be supported alongside 4G on an Evolved
Packet Core which is increasingly likely to be built on virtualised hardware. As with
the architecture of earlier generations of mobile networks, 5G architecture is represented as functional blocks and the interfaces (or reference points) between
them.

The functional blocks are split between control plane (e.g. authentication, data
management, access and mobility management) and user plane functions (e.g. user equipment, the radio access network (RAN) and the data network) with the control plane further split between subscriber management functions and control plane functions.

In addition to representing the architecture as functional blocks with defined interfaces, 3GPP has also defined a service Based Architecture which takes advantage of recent developments in Network Functions virtualisation to propose a network based on virtualised infrastructure. The solution will sit on common computer hardware and call upon resources as required.

The RAN is represented as a single functional entity whereas in reality the realisation of a 5G RAN is not so straightforward. In 2G and 3G a network controller provided an interface between the RAN and the core network hiding a lot of signalling from the core and managing complex RAN functions.

With 4G there was no network controller but rather the functions were managed in
the RAN. 5G effectively introduces a centralised RAN node albeit not a network controller as such. The 5G radio base station is split into a distributed and a centralised unit with the details of the split being a topic of much industry debate.

The increasing demands for ever higher peak and average data rates, greater area
capacity density, lower-latency and enhanced performance will drive a more
distributed next-generation core network.

As functions of the RAN moves towards the core, certain core functions will move
towards the RAN to facilitate services which are enabled from on-net infrastructure such as distributed user plane functions, multi-Access Edge Computing and content distribution networks.

Chipset vendors are indicating that 5G NRcapable smartphones will be available from some manufacturers during mid-tolate 2019 and therefore it’s likely that
mainstream mobile-centric 5G network services will commence in many markets
in and around the year 2020.

This is a summary of the full article which appeared in The Journal Volume 12. 

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