6G USE CASES &
TECHNOLOGIES
DRIVING THEM
Expanding upon the foundation of 5G, 6G will enable a much wider set of futuristic use cases that, when deployed on a massive scale, will transform the way we live and work in remarkable ways.
Telecom operators, technology providers, and academia are joining forces under various alliances and consortia. They are deliberating on which use cases will emerge in the next decade, and be adopted by 6G. NGMN [2], Next G Alliance [3], and one6G [4] are just some of the leading alliances that have recently published 6G use cases.
Figure 7 shows the categorization of various 6G use cases that enhance human-to-human, human-to-machine, machine-to-machine, and machine-to-human communication.
Figure 7: Emerging 6G use cases
1. Sub-terahertz SpectrumThe 6G era may necessitate a 20X increase in network capacity. 6G is likely to meet this challenge through new spectra in the range of 7 to 24 GHz and the sub-THz range (larger than 100 GHz), using ultra-massive MIMO.
Figure 8: 6G sub-terahertz spectrumSource: https://www.miwv.com/what-is-6G/
2. Cell-free Network Architecture
Cell-free architecture eliminates the traditional cellular structure, by combining the advantages of distributed systems and massive MIMO. Instead of having fixed cell boundaries and specific base stations serving particular areas, cell-free network uses a distributed network of access points (APs) that communicate with each other to coordinate their transmissions and avoid interference to serve users in a wide area. This allows more efficient use of spectrum, lower latency, higher throughput, improved energy efficiency and better coverage than current 5G networks.
Figure 9: 6G cell-free network architectureSource: SK Telecom, South Korea
3. 6G Non-Terrestrial Networks (NTNs)
While 5G cellular commercial deployment is a reality now, it has been always a challenge to provide adequate broadband coverage to rural regions. In addition, in many developed countries, existing cellular infrastructures are vulnerable to natural disasters. They may also lack the reliability, availability, and responsiveness required by future wireless applications. Network densification could be one way to increase network resiliency, but it will also inevitably lead to an energy crunch, with serious economic and environmental concerns.
3GPP defines NTN as networks, or segments of networks, using an airborne or spaceborne vehicle for transmission. Geostationary satellites (GEO), low earth orbit satellites (LEO), medium earth orbit (MEO) and high-altitude platform satellites (HAPS) have proven very beneficial in providing on-demand cost-effective coverage for crowded and unserved areas.
Though communication between satellites has existed for decades, the solutions have been proprietary. Standardization in 3GPP is likely to grow the ecosystem faster. The inclusion of NTN use cases and deployment options into the 3GPP technology feature roadmap is a best practice example of how vertical industries can actively push boundaries and get vital tech included in an evolving standard.
Various corporations and consortia (e.g. Amazon’s Project Kuiper, OneWeb, Telesat and Starlink) started deploying internet services from 2021, with current deployments ranging from a few dozen to hundreds of satellites, and some are targeting more than 10,000 in the future.
Among all these different aerial systems, HAPS have been gaining attention, due to their improved coverage in rural areas. HAPS networks offer wide coverage and large capacity to serve highly populated suburban and rural areas, as well as isolated areas with weak connectivity - supplementing current wired and wireless infrastructure.
NTNs and HAPS are being investigated as key parts of the 6G framework, supporting global, ubiquitous, and continuous connectivity, and overcoming the coverage limitations of 5G networks. With all the recent advancements in emerging technologies - like the development of new aerial/space architectures, and innovative spectrum and antenna technologies - NTNs are likely to see more widespread adoption.
6G will provide reliable networking connectivity, focusing on improved performance and ubiquitous coverage, through the seamless integration of non-terrestrial networks (like satellites, drones, and HAPS) with the terrestrial network. Please see figure 10 for more information.
Figure 10: 6G Non-Terrestrial Networks (NTN)Source: Whitepaper: Non-Terrestrial Networks in 5G & Beyond A Survey
Figure 11: 5G NTN use casesSource: Whitepaper Non-Terrestrial Networks in 5G & Beyond A Survey
Future 6G networks are expected to go beyond mobile or RAN. They will be capable of integrating a variety of new access networks, like the non terrestrial networks discussed here, along with the proliferation of edge computing devices - exploiting the interconnection and federation of those edges.
Figure 12: Future Network Access and Edge architecture Source: ITU-T FG-NET2030, 2020
In addition, 6G networks are expected to be able to coordinate services with private networks. This would allow such private networks to use secure public networks as an offloading mechanism during periods of high demand.
4. AI & ML as a key enabler
The complexity of 6G communication technologies and network deployments will probably prevent closed-form and/or manual optimizations. So, one of the foundational differences will be in the role that ‘intelligence’ will play in 6G networks. While intelligent techniques in cellular networks are already being discussed for 5G, we expect 6G deployments to be much denser (i.e., in terms of the number of access points and users), more heterogeneous (in terms of the integration of different technologies and application characteristics), and with stricter performance requirements.
Therefore, intelligence will play a more prominent role in the network, going beyond the classification and prediction tasks which are being considered for 5G systems. The 6G standard may not specify the techniques and learning strategies to be deployed in networks, but data driven approaches can be seen as tools that network vendors and operators can use to meet 6G requirements.
AI will become a native ingredient in 6G networks, allowing these networks to become fully autonomous and to hide their increased network complexity from end users. A dynamic AI/ML-defined native air interface will be key to future networks. These interfaces could give radios the ability to learn from one another and their environments.
Figure 13: AI/ML algorithms and applications for mobile networks
5. New Network Services
One key aspect identified by ITU-T is the emergence of ‘time engineered’ networks, in which a certain latency for data transfer is guaranteed - thus minimizing delays. These time engineered networks offer In-Time, On-Time and Coordinated Guarantees, and such guarantees allow time engineered networks to provide services that have a variety of specialist timing requirements.
For example, a Coordinated Guarantee service could facilitate holographic communication. As holographic communication requires the precise coordination of image, voice, video and haptic devices, all of which have different tolerances to delay. Alternatively, an In-Time Guarantee, which ensures that latency is almost always the same (with a small tolerance) could be used to help control a UAV swarm.
By combining the different kinds of data services given above, 6G networks are expected to cater to increasingly complex and data-hungry use cases. Using holographic communications as an example again, massive bandwidth, combined with low latency, will be required in dense environments where the local competition for data is strong.
Seamless data consumption from the network will be possible with the creation of specific APIs, that enable an application to expose its capabilities to the host network (‘exposability’). This will help to create a bridge between the application and the supporting network infrastructure - allowing it to draw exactly the data it needs. Concepts like this exposability and programmability [14] are expected to be factors in 6G.
Figure 14: ITU-T vision about time engineered services in Source: Network 2030 blueprint (FG-NET2030, 2019)
6. Sustainability as a key driver
By designing 6G around AI/ML-based solutions, it may be possible to achieve as much as a 50% reduction in transmit power over 5G for the same bandwidth and data rate.
Figure 13: Technologies enabling a sustainable 6G network
Intelligent Reflecting Surfaces (IRS) are another promising technology that can accelerate energy saving and sustainability. An IRS is a thin panel that possesses many independently controllable passive reflection elements. It can improve the security, spectrum, energy efficiency, and coverage of 6G networks, by adjusting the amplitude and phase shifts of reflective elements on the panel’s surface. This allows it to achieve fine-grained reflect beamforming, which can be deployed at the cell edge to help improve the desired signal power and also suppress interference, thus creating a signal hotspot, as well as an interference-free zone in its vicinity.
