By Subhankar Pal, Global Research & Innovation Leader for Future of Networks, Capgemini Engineering.

Each new generation of technology is an opportunity to overcome the shortcomings of its predecessors and stake out new use cases. 6G is no exception to that rule, including for how it will —finally — bring true broadband speeds to even the most remote, sparsely populated areas.

There’s no doubt that 5G is making impressive gains in both network launches and subscriber additions. Between Q1 and Q2 of 2021, 5G subscriptions increased 41 percent, or 124 million, for a global total of 429 million, according to Omdia. The research firm also says 5G is on track to hit 700 million by the end of this year. Meanwhile, TeleGeography predicts that the number of commercial 5G networks will hit 220 by the end of 2021 and 323 by the end of 2023.

But even at that rate, 5G will cover only 40 percent of the world by 2024,  as per GSMA. That means people, schools, businesses, hospitals and others in the remaining 60 percent won’t have access to gigabit downloads, single-digit-millisecond latency and other major features.

Understanding why 5G will continue to fall short, long after 2024 also means understanding why 6G will strive to provide 100 percent coverage to connect the unconnected. Like its predecessors, 5G is held back by its terrestrial-centric design. Its reliance on towers and small cells means it will always be unable to serve users in places such as an oil rig or cruise ship in the middle of the ocean. It also struggles to reach remote places on land, such as the Himalayas and other mountainous regions where installing towers is virtually impossible.

6G’s pioneers — such as the European Commission’s Hexa-X 6G initiative and ATIS’s Next G Alliance — recognize this fundamental limitation and are working to ensure that 6G can be deployed in more than just the traditional terrestrial cellular architecture. 6G also will be designed to support non-terrestrial networks (NTN) such as LEO, MEO and GEO satellites, drones and high-altitude platform systems (HAPS). All of this will ensure seamless, wide-scale coverage over large geographical areas, including mountain ranges, deserts and oceans. Read more about NTN in 6GWorld: The Future of 6G is Up in the Air — Literally.

6G also will use new spectrum to maximize coverage and data rates. For example, terahertz spectrum will enable terabit speeds.

“The opening up of sub-terahertz and terahertz spectrum is one area of 6G research that is attracting interest due to the potential for these frequencies to provide very wide bandwidths that could support terabits-per-second transmission,” Analysys Mason says. “The FCC has already opened up terahertz spectrum (above 95 GHz) in the USA. The regulator in the UK, Ofcom, also consulted on making frequencies above 100GHz available.”

Finally, 6G also will use intelligent reflective surfaces, massive antenna arrays and advanced beamforming. These also will help achieve centimetre-level positioning accuracy.

6G will introduce ultra-Massive MIMO (UM-MIMO). UM-MIMO will have massive antenna arrays that integrate a very large number of nano-antennas (1024 and higher) in very small footprints (e.g., 1 mm²) for achieving extremely high data rates at THz-band frequencies.

6G will also see use of highly energy efficient, sustainable, environmentally friendly technology solutions like Intelligent Reflective Surface (IRS). This will be installed on large flat surfaces e.g., walls or ceilings indoors, buildings or signage outdoors, to reflect radio-frequency energy around obstacles and create a virtual line-of-sight propagation path between a Terahertz source and the destination. The meta-material in IRS lets the surface adjust its characteristics to reflect a signal to a desired destination, in order to improve the performance of wireless data transmission and positioning accuracy.

A New Era of Holographic Teleportation and More

6G’s 1 Tbps peak speeds, 100 µs latency, 3 b/s/Hz spectral efficiency, LEO satellite interworking and other advanced capabilities will enable a wide variety of applications and use cases that 5G will never be able to support because of its legacy foundation. Some potential examples include:

• Holographic teleportation: This needs bandwidth of 1 Tbps or more for full 3D virtual representation. 5G maxes out at 200 Gbps.

• Space tourism: This will require connectivity for crew and passengers more than 100 km above Earth. 5G can reach only about 3,000 feet up. By supporting interworking with LEO satellites, which are situated in the altitude of 300 km to 1500 km, 6G will play a key role in extending cellular networks to space.

• Deep-sea communications: Radio signals die rapidly in water. Sonar signals sent by underwater devices mostly reflect off the surface without ever breaking through. 6G’s use of new spectrum such as visible light will provide seamless, high-speed connectivity under water for deep-sea explorations and more.

• Vehicular communications: Level 5 autonomous vehicles need sub-millisecond communication latency. 5G latency is in the range of 1-4 milliseconds.

• 6G localisation and sensing: Use cases such as drone delivery, asset tracking, health care monitoring, precision agriculture and autonomous vehicles need centimetre-level positioning accuracy. 5G position accuracy is still in the order of meters.

Another key difference is that 5G is focused machine-to-machine use cases such as IoT, whereas 6G will make humans the center of attention. Examples include multi-sensory extended reality and body-area networks.

The Path Forward

The Next G Alliance and Hexa-X 6G initiative are just two examples of the work underway to enable these use cases and technology advances such as satellite interworking. Japan’s government is providing ¥50 billion for 6G R&D, while China created a national 6G R&D working group.

The onus is on the industry to lead harmonisation efforts on 2030 system vision, technology trends and requirements in international forums such as ITU-R, GSMA and NGMN. 3GPP, the ITU and other standards bodies are studying how satellites, HAPS and drones can be brought into the realm of 6G networks. All of that work suggests 6G has a bright future.