While 5G roll-out is barely beginning in many markets, the USA and China are squaring up over 6G as a major focal point for their global competitiveness, both eyeing up 2030 for first deployments.
China first identified this date as a target for first availability of commercial services back in 2018 when the country began 6G research, firming up on this in a paper published early June 2021 by the government-backed China Academy of Information and Communications Technology (CAICT). This paper set out three core use cases and 10 key technical developments that would underpin them.
Then three months later, the USA’s Alliance for Telecommunications Industry Solutions (ATIS) staged its inaugural 6G Summit in Denver on August 31. This was a US-centric event designed to forge the country’s path towards 6G and close the gap on China that was perceived to have opened up in early 6G R&D.
The field is not just confined to the USA and China though, noting that South Korea’s LG claimed a breakthrough in August 2021 by demonstrating transmission in the terahertz spectrum in Berlin, Germany, collaborating with that country’s Fraunhofer-Gesellschaft research institute. At the same time, LG announced it had developed the adaptive beamforming and high-gain antenna switching technologies that will be required for 6G communications at such high frequencies.
This raises the question of what 6G will be and how it will differ from 5G. After all, 5G has been arguably oversold so far to consumers as being revolutionary when in its early implementations, only incremental speed and capacity improvements are delivered, or very patchy coverage. Nonetheless, there is a sense that 5G will over time deliver a radically improved quality of experience or service in both the commercial and enterprise spheres, placing mobile infrastructures as vital strategic assets.
In that context, 6G can be regarded more as unfinished 5G business and a continuum as services progress further up the frequency ladder and fill in technology gaps needed to deliver some of the promised benefits or use cases.
This appears to be how the Chinese see it, with that CAICT white paper identifying three emerging developmental themes – immersive, intelligent and universal – fanning out into eight business application areas. The latter include immersive cloud XR, holographic communication, sensory interconnection, intelligent interactive communication, digital twins, and general enhanced global coverage.
These in turn can be sub-divided by vertical sector and then into specific applications within them. Immersive services can be factored into entertainment, healthcare and industrial edge services.
There is little difference between the various parties over this breakdown, with consensus also over the need to extend communications not just into THz bands, but also into the optical domain, in order to meet ever growing demands for mobile data capacity. Holographic communications or projection and XR will generate further massive increases in data that will eventually overwhelm even dense millimeter wave 5G infrastructures.
We have discussed before the potential benefits and challenges of wireless communication at THz frequencies, which will require even smaller antennas suffering potentially from high losses, made worse by declining precision in fabrication. On the other hand, the smaller size enables denser antenna designs and more massive beamforming to mitigate interference and maximize capacity. Research has focused on overcoming those design and fabrication challenges, with some success already.
Even so, there is growing conviction that optical communications over-the-air will feature increasingly to cater for ever rising demand, given a sense that eventually RF transmission will run out of road, with a limit to how high frequencies can go. Optical communications have challenges of their own, which is one reason why RF has been preferred so far. Yet, the potentially enormous bandwidths and other benefits such as flexibility and convenience in the field have driven research here too to overcome the problems.
Fiber still has scope for further improvements but is costly to deploy and not suitable in all scenarios and domains. The complementary field of non-guided optical communication is split into two, free space optics (FSO) and optical wireless communications (OWC). FSO refers to focused communication between optical wireless units, each comprising an optical transceiver, housing transmitter and receiver to provide full-duplex transmission. Each optical wireless unit also incorporates a lens unit, like a telescope, that focuses the light into a beam for transmission through free space, meaning either the atmosphere, outer space, or even a vacuum on the ground.
OWC uses unguided light, either visible, infrared, or ultraviolet. When using light in the visible band (390–750nm), it is usually called visible light communication (VLC). 6G development plans sometimes refer to FSO and then VLC as a subset of OWC. Generally, OWC operates at shorter range and has potential for underwater transmission for example where RF does not work.
FSO, on the other hand, could be used for longer range and has been proposed for fronthaul and backhaul 5G services even before 6G. A challenge here is to overcome attenuation resulting from atmospheric phenomena, especially fog, requiring accurate pointing and acquisition of signals. Adaptive beam control mechanisms are being developed to overcome these challenges, as discussed in a paper on the subject in IEEE Future Networks Tech Focus, Airborne Free-Space Optical Communications for Fronthaul/Backhaul Networks of 5G and Beyond – IEEE Future Networks.
At the purely technological level then, we are not witnessing a fundamental split in cellular development, more just a duplication of effort that moves the world yet further away from the long-held ambition, or more like a dream, held by the GSMA of global platforms built to common standards drawing on innovations wherever they came from, without being penalized by punitive royalties.
However, as we have discussed before, the USA’s deteriorating relationship with China threatens disruption to standards processes and international cooperation in organizations such as 3GPP. That could delay or weaken future 5G and especially 6G standards as they emerge around or after 2025, even leading to the mobile world splitting into two regional camps, with a return to the old days of GSM versus CDMA.
In particular, the early 6G efforts are becoming mixed up with the US-China political and technology wars, but also with efforts by the cellular ‘Old World’ – the countries like Japan, Korea, Finland and Sweden that contributed so heavily to the earlier mobile platforms – to defend their influence. The USA itself has threatened the dominance of those four but is in turn being challenged not just by China but also India with it made at home campaign and ambitions to become a major force in mobile, despite being late into 5G.