It seems only yesterday that the seminal 5G white paper, published by the NGMN Alliance, was issued, setting out many of the key assumptions about the new generation of mobile technology. In fact, it was almost five years ago, which seems to be long enough for the industry to have moved on to ‘6G’, and the first white paper seeking to define what that will entail.
The paper has been published by the 6G Flagship research program, which says the document “opens the floor for defining the 2030 wireless era”. This may be ambitious when most stakeholders are still struggling with what 5G will mean for networks and business models, but the authorship is credible. The paper is based on inputs from 70 engineers and other experts who took part in a workshop at the first 6G Wireless Summit, held in March in Finnish Lapland.
Most R&D labelled as 6G, to date, has centered on pushing standards-based mobile communications even further up the spectrum than 5G, into frequencies above 100 GHz (confusingly known as ‘terahertz’).
But this paper is trying to set out the initial parameters for a broader view of what 6G might entail, including commercial and technical drivers, R&D requirements, and the key challenges and questions that need to be addressed in mapping out a 6G agenda.
Professor Matti Latva-aho, director of the 6G Flagship program – which is based at the University of Oulu in northern Finand – edited the paper with a colleague, Professor Kari Leppänen. Latva-aho said: “As 5G research is maturing and continues to support global standardization, we must already engage in mapping what 6G can become at its boldest.”
Many of the topics raised in the paper are little different from those set out for 5G – the need for both platforms will be driven by the need to process and consume more and more data, at every possible micro-location, and to enable fully ubiquitous connectivity. Once that is achieved, new experiences such as fully immersive ‘extended reality’ become more possible and affordable.
“Intelligence will create context-aware smart services and applications for human and non-human users alike,” says the paper – something that is frequently said about 5G.
The social-economic drivers also sound similar to those set out in many nations’ 5G vision papers. This white paper bases its 6G list on the United Nations’ Sustainable Development Goals (SDGs).
It also outlines new operating models that 6G could enable – but which are already emerging as part of the 5G picture. For instance, it says: “The increasing role of indoor networks will boost network sharing in cities and indoor spaces, and – especially – drive the ‘local operator’ paradigm. Stakeholder roles in 6G will change compared to the current mobile business ecosystem and new roles will emerge.”
So what is new in this paper? As with early 6G R&D projects, that is mainly about new spectrum bands, which can deliver even greater capacity than the millimeter wave frequencies in which 5G can be deployed – and therefore push the immersive, massive-data services to an even more extreme level, enabling new, pervasive ‘XR’ devices which could replace smartphones. By 2030, as an example, “telepresence will be made possible by high resolution imaging and sensing, wearable displays, mobile robots and drones, specialized processors, and next generation wireless networks. Autonomous vehicles for ecologically sustainable transport and logistics are made possible by advances in wireless networks and in distributed artificial intelligence (AI) and sensing.”
It is not a criticism that the first 6G paper does not seek to create a grand vision of a post-5G future. It is actually reassuring to think about mobile platforms and services as an ever-evolving continuum rather than a once-a-decade forklift. But we can question why 6G R&D, in its current form, is not presented as a continuation of 5G – not a ‘new G’ but an expansion of 5G into higher and higher frequencies. But perhaps a new label works better for engaging interest and the best participants in the project. The group is already calling on “company representatives, researchers, decision makers, and other builders and members of smart society” to join the effort and take part in the next summit, on March 17-20.
And in the context of current technology wars between east and west, and battles to control IPR, it may be significant that a program based in the homeland of Nokia is seeking to seize the initiative from other projects based in China. It is to be hoped that political tensions ease so that the early terahertz and ‘6G’ efforts can cooperate more than compete in the 2020s, because the use of very high frequencies to enable new experiences, services and ultimately revenue models will be a highly complex topic of research.
The so-called terahertz spectrum, in cellular terms, ranges from 100 GHz to 540 GHz). Some of the projects which are already under way include:
University of California, Irvine (UCI) – its Nanoscale Communication Integrated Circuits lab has demonstrated a wireless transceiver chip which can send signals in frequencies above 100 GHz, claiming lower cost and power consumption than existing designs. The UCI team has built a 4.4-square millimeter receiver chip that claims to achieve new levels of energy efficiency as well as speed, compared to other prototypes that have been demonstrated. It does this by using a new digital-analog architecture that significantly relaxes digital processing requirements.
Traditionally, changing the frequencies of signals through modulation and demodulation is done via digital processing, but this is running up against the limitations of Moore’s Law because transistors are reaching the stage where they cannot be made any smaller. “You cannot break electrons in two, so we have approached the levels that are governed by the physics of semiconductor devices,” said the Labs team. Instead, they carry out modulation of digital bits in the analog and RF domains, avoiding the need for energy-guzzling high resolution data converters, and reducing cost. The prototype consumes total DC power of 200.25mW.
New York University’s (NYU’s) Wireless Research Center. Professor Ted Rappaport, the founding director of NYU Wireless, believes recent technological developments such as those in quantum computing and nanotechnology will make the terahertz spectrum more usable in future.
The European Union is supporting, under the auspices of its Horizon 2020 program, a project called iBROW (innovative ultra-broadband ubiquitous wireless communications through terahertz transceivers), led by the University of Glasgow, UK. The project’s aim is to develop an energy-efficient and compact ultra-broadband short-range wireless transceiver technology. While the current focus is on 60 GHz, which is already in commercial use, in future there is the potential to move higher up the spectrum, as far as 1 THz.
Nokia was one of the founders of the mmWave Coalition, which despite its name, has been established to lobby US agencies such as the FCC, international regulators and the International Telecommunications Union (ITU), to open up bands above 95 GHz. Other founders include testing firm Keysight Technologies and Virginia Diodes.
One of ETSI’s Industry Specification Groups, called mWT, was set up to promote the use of spectrum from 50 GHz up to 300 GHz for present and future critical transmission use cases.
The IEEE, home of the standards which underpin WiFi and Bluetooth, is also active in this area, via its 802.15 WPAN Terahertz Interest Group (IGTHz).
In early 2017, researchers in Japan said they had developed a transmitter which could achieve data rates of over 100Gbps over a single channel in the 300 GHz band, creating true ‘wireless fiber’. The team of scientists from two academic institutions (Hiroshima University and the National Institute of Information and Communications Technology) plus Panasonic, said the technology enables data rates “10 times or more faster” than 5G. The group claims that terahertz wireless links to satellites could make gigabit speeds available around the world, even on planes in flight.
What is the terahertz spectrum?
Professor Ted Rappaport, director of NYU Wireless, explains that, despite its name, the terahertz band is generally restricted, for potential commercial mobile usage, to the area between 100 GHz (where mmWave leaves off) and 540 GHz. “Technically, the terahertz band is 300 GHz to 3000 GHz, but due to the molecular make up of air, the spectrum that is implied by ‘THz’ in the circuits and sensing and communications realm is, practically speaking, in the range of from 100 GHz to 540 GHz or so, and the term ‘THz’ is now being loosely used to describe frequencies ‘above 100 GHz’.”
Similarly, mmWave is technically between 30 GHz and 300 GHz, but for practical purposes, in the cellular industry, is deemed to be above 10 GHz and up to 100 GHz.