Mm-wave antenna array developed in an earlier project paves the way towards even smaller dimensions of THz communications and sensing

University of Oulu is at the top of 6G research - "The university's task is to look forward"

The 6G research programme at the University of Oulu is one of the first ones in the world. "Again we have to do things that we cannot really do yet. That is the purpose of science", Professor Aarno Pärssinen says when faced with the challenge.

The Academy of Finland's decision to select 6G-Enabled Wireless Smart Society & Ecosystem -cluster of expertise led by the University of Oulu as the research flagship is a recognition of persistent, long-term work.

- This 6G funding was granted on the basis of long-term evidence. Persistent work in telecommunications and electronics started in Oulu already in the 1990s, and has continued ever since, Professor Timo Rahkonen states.

Receiving funding for an eight-year project in Oulu is also a recognition to the city.

- Oulu is, in a positive sense, a great example of a city of engineers. We have a very understanding environment here, and a strong will to work. Entrepreneurship thrives in Oulu, which is also very visible at the University. Oulu people are resilient enough to develop long-term research, Professor of Radio Technology at the University of Oulu Aarno Pärssinen enthuses.

Dialogue and cooperation with the industry have also taken the University of Oulu forward.  Universities need cooperative partners. Cooperation has achieved a lot and we have been able to offer new innovations to the industry. Pärssinen thinks that the university's task is to look forward.

"The university's task is to look forward."

- We have built the programme in Oulu around 6G technology. 5G is yet to be launched and there is a lot of industrial activity around it, but the academic world is already gradually entering the sixth generation. It is time for us to start thinking ten years forward, bearing in mind that there will be many 5G research challenges for a long time ahead in terms of radio standards and supporting the further development of better products.

Focusing on the whole

There is a great demand for new solutions, and experts are needed. The University of Oulu offers an excellent test environment with a focus on the RF technology, in other words, the facilities for the work of top researchers are in tip top shape.  The university’s research programme focusing on 6G technology is one of the first, if not the very first, of its kind in the world with such an extensive scope.

- Of course some of our research areas related to 6G technology are also being studied in Europe, the United States and to a certain extent in the Far East. But our focus is on that we look at communications, radio systems and all related aspects from applications to the implementation technologies and electronics as one whole entity, and try to understand what kind of system could be built for the needs after 5G, explains Pärssinen.

The higher the frequencies, the shorter the wavelengths

6G technology goes to higher frequencies than 5G, and the wavelength shortens.

- 2G, 3G and 4G have used frequencies that reach approximately up to 6 GHz. One gigahertz equals to 30 centimetres in wavelength.  5G systems use the range of less than 6 GHz as efficiently as possible. The first commercial systems will expand this to the area of 24-40 GHz, and will be able to reach almost 100 GHz. We have determined this as the 5G range. That is when we talk about millimetre wave technology, in other words, the wavelength is in centimetres or millimetres. In 6G, we are about to jump above 100 GHz and see what happens. And so, the area of interest will be from 100 GHz to a terahertz, which means another big step forward. There will be so much frequency available that it can contain an absurd amount of data. Data intensity will not only be increased in information technology, but also in terms of its wireless transport, explains Pärssinen.

Renewing aerials and circuits

Wireless connections require a lot from infrastructure as they have to pass through walls.

- We must come up with, once again, a solution that makes this reasonable and physically possible in those frequencies. It is a risk and opportunity that we take. Again, we need to do things that cannot really be done yet. But that is the purpose of science. The goal is to make new things in frequencies that have enabled significant advances in radio astronomy and other scientific or otherwise very demanding applications. Now the focus is on harnessing this for commercial use in reasonably priced, small devices, and how to get the radio signal to travel in this environment.

There are plenty of challenges. The antenna, for one, must also be invented again.

- The antenna is a component proportional to wavelength.  We started the GSM with the wavelength of 30 centimetres that has impact to minimum device size, and now we are talking about millimetre-sized structures that must be designed reliably with electrical tools. We must also be able to connect them together with electronics. We are talking about dimensions varying in proportion from nanometres to a few dozen, maybe a few hundred micrometres. Such a resolution enables the placement of thousands and millions of transistors in the same circuit, and emitting the information out to ‘the sky’ with antenna technology for the needs of wireless communication, explains Pärssinen.

There are only a handful of manufacturing plants for producing fast integrated circuits in the world.

Professor Timo Rahkonen

- Constructing fabrication plants for the production of the fastest circuits is so expensive that there are only a handful in the whole world. They are built in places where no earthquakes take place and trains do not pass close by, as the ground should not vibrate. The processes are developed for highest product volumes. For the time being, the largest volumes are in the computer circuits. In other words, many of the processes used are tuned in the design of digital circuitry, explains Professor Timo Rahkonen.

The opportunity to study at the top of development

The University of Oulu already has one of the world's first 5G test networks, which is used by the students in many different ways. Towards the end of the eight-year project, the University of Oulu should have the first 6G test networks. The students will have a great opportunity to take advantage of top RF development.

The RF engineering study option is included in the master’s program focusing on deep understanding of RF, RFIC, antennas and wireless transceiver system level design. The option provides also basic information of radio channels, digital signal processing and telecommunications. On the top of deep understanding related to RF engineering, today an RF designer needs also information of analog circuit design and IC technologies. With this new RF study option we will provide skills and knowledge required to design future wireless communication systems.

Towards the visions

It is as yet unknown, what 6G will be able offer the industry and ordinary consumers. However, there are some visions. Short-wave technology can be utilised, for example, in medicine for finding cancer cells, improving safety in traffic and in marine navigation.

- We could find something, which has not yet been extensively used in traditional radio technology. So far, the radio transmits something in one direction and the receiver captures it. Now we are moving towards the MIMO multiple-antenna system, which shoots data into several directions, and takes advantage of the reflections. With such a technique, it may be possible to construct an image of the environment. While being connected to your base station, you can begin to receive a physical image of the environment. That will certainly create more imaging opportunities. The terahertz region has been used for some time at airport security checks, to avoid X-raying people, says Rahkonen.

Main image: Mm-wave antenna array developed in an earlier project paves the way towards even smaller dimensions of THz communications and sensing. Image: Hanna Saarela.

Text and pictures: Ari Kettunen

Last updated: 9.8.2018