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With 5G Rollout Lagging, Research Looks Ahead to 6G

The new technologies and capabilities of 6G could fulfill and expand on 5G promises

3 min read
A person standing on a mountain dreaming of a 6G network.
Photo: iStockphoto

Amid a 5G rollout that has faced its fair share of challenges, it might seem somewhat premature to start looking ahead at 6G, the next generation of mobile communications. But 6G development is happening now, and it’s being pursued in earnest by both industry and academia.

Much of the future landscape for 6G was mapped out in an article published in March of this year in an article published by IEEE Communications titled “Toward 6G Networks: Use Cases and Technologies.”  The article presents the requirements, the enabling technologies and the use cases for adopting a systematic approach to overcoming the research challenges for 6G.

“6G research activities are envisioning radically new communication technologies, network architectures, and deployment models,” said Michele Zorzi,  a professor at the University of Padua in Italy, and one of the authors of the IEEE Communications article. “Although some of these solutions have already been examined in the context of 5G, they were intentionally left out of initial 5G standards developments and will not be part of early 5G commercial rollout mainly because markets are not mature enough to support them.”

The foundational difference between 5G and 6G networks, according to Zorzi, will be the increased role that intelligence will play in 6G networks. It will go beyond merely classification and prediction tasks as is the case in legacy and/or 5G systems.

While machine-learning-driven networks are now still in their infancy, they will likely represent a fundamental component of the 6G ecosystem, which will shift towards a fully-user-centric architecture where end terminals will be able to make autonomous network decisions without supervision from centralized controllers.

This decentralization of control will enable sub-millisecond latency as required by several 6G services (which is below the already challenging 1-millisecond requirement of emerging 5G systems). This is expected to yield more responsive network management.

To achieve this new kind of performance, the underlying technologies of 6G will be fundamentally different from 5G. For example, says Marco Giordani, a researcher at the University of Padua and co-author of the IEEE Communications article, even though 5G networks have been designed to operate at extremely high frequencies in the millimeter-wave bands, 6G will exploit even higher-spectrum technologies—terahertz and optical communications being two examples.

At the same time, Giordani explains that 6G will have a new cell-less network architecture that is a clear departure from current mobile network designs. The cell-less paradigm can promote seamless mobility support, targeting interruption-free communication during handovers, and can provide quality of service (QoS) guarantees that are in line with the most challenging mobility requirements envisioned for 6G, according to Giordani.

Giordani adds: “While 5G networks (and previous generations) have been designed to provide connectivity for an essentially bi-dimensional space, future 6G heterogeneous architectures will provide three-dimensional coverage by deploying non-terrestrial platforms (e.g., drones, HAPs, and satellites) to complement terrestrial infrastructures.”

Key Industry and Academic Initiatives in 6G Development:

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Metamaterials Could Solve One of 6G’s Big Problems

There’s plenty of bandwidth available if we use reconfigurable intelligent surfaces

12 min read
An illustration depicting cellphone users at street level in a city, with wireless signals reaching them via reflecting surfaces.

Ground level in a typical urban canyon, shielded by tall buildings, will be inaccessible to some 6G frequencies. Deft placement of reconfigurable intelligent surfaces [yellow] will enable the signals to pervade these areas.

Chris Philpot

For all the tumultuous revolution in wireless technology over the past several decades, there have been a couple of constants. One is the overcrowding of radio bands, and the other is the move to escape that congestion by exploiting higher and higher frequencies. And today, as engineers roll out 5G and plan for 6G wireless, they find themselves at a crossroads: After years of designing superefficient transmitters and receivers, and of compensating for the signal losses at the end points of a radio channel, they’re beginning to realize that they are approaching the practical limits of transmitter and receiver efficiency. From now on, to get high performance as we go to higher frequencies, we will need to engineer the wireless channel itself. But how can we possibly engineer and control a wireless environment, which is determined by a host of factors, many of them random and therefore unpredictable?

Perhaps the most promising solution, right now, is to use reconfigurable intelligent surfaces. These are planar structures typically ranging in size from about 100 square centimeters to about 5 square meters or more, depending on the frequency and other factors. These surfaces use advanced substances called metamaterials to reflect and refract electromagnetic waves. Thin two-dimensional metamaterials, known as metasurfaces, can be designed to sense the local electromagnetic environment and tune the wave’s key properties, such as its amplitude, phase, and polarization, as the wave is reflected or refracted by the surface. So as the waves fall on such a surface, it can alter the incident waves’ direction so as to strengthen the channel. In fact, these metasurfaces can be programmed to make these changes dynamically, reconfiguring the signal in real time in response to changes in the wireless channel. Think of reconfigurable intelligent surfaces as the next evolution of the repeater concept.

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