Smart Surface Sorts Signals—The "Metaprism" Evaluated

Reflective microwave meta-mirror could offer unique solution for next-generation wireless networks

2 min read
Theoretical model of a signal reflected by the metaprism, in which each frequency is reflected in a different direction.
Example of signal reflected by the metaprism, whereby each sub-carrier is reflected in a different direction.
Image: University of Bologna

The search for better ways to optimize and direct wireless communication is never-ending. These days the uses of metamaterials—marvels of material science engineered to have properties not found in naturally-occurring stuff—also seem to be similarly boundless. Why not use the latter to attempt the former? 

This was the basic idea behind a recent theoretical study, published earlier this month in IEEE Transactions on Wireless Communications. In it, Italian scientists describe a means of directing wireless communication signals using a reflective surface made from a metamaterial. This meta “prism” differently redirects microwave and radio signals depending on their frequencies, much the way conventional prisms bend light differently depending on a light beam’s color.

Earlier generations of wireless networks rely on lower frequency electromagnetic waves that can easily penetrate objects and that are omni-directional, meaning a signal can be sent in a general area and does not require a lot of directional precision to be received.

But as these lower frequencies became overburdened with increasing demand, network providers have started using shorter wavelengths, which yield substantially higher rates of data transmission—but require more directional precision. These higher frequencies also must be relayed around objects that the waves cannot penetrate. 5G networks, now being rolled out, require such precision. Future networks that rely on even higher frequencies will too. 

Davide Dardari is an Associate Professor at the University of Bologna, Italy, who co-authored the new study. “The idea is rather simple,” he says. “The metaprism we proposed… [is] made of metamaterials capable of modifying the way an impinging electromagnetic field is reflected.” 

Just like a regular prism refracts white light to create a rainbow, this proposed metaprism could be used to create and direct an array of different frequencies, or sub-carrier channels. Sub-carrier frequencies would then be assigned to different users and devices based on their positioning.

A major advantage of this approach is that metaprisms, if distributed properly around an area, could passively direct wireless signals, without requiring any power supply. “One or more surfaces designed to act as metaprisms can be deployed in the environment, for example on walls, to generate artificial reflections that can be exploited to enhance the coverage in obstructed areas,” explains Dandari.

He also notes that, because the metaprism would direct the multiple, parallel communication channels in different directions, this will help reduce latency when multiple users are present. “As a [result of these advantages], we expect the cost of the prisms will be much lower than that of the other solutions,” he says.

While this work is currently theoretical, Dandari plans to collaborate with other experts to develop tailored metamaterials required for the metaprism. He also plans to explore the advantages of the metaprism as a means of controlling signal interference.

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Photo: George Frey/AFP/Getty Images
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We've all been told that 5G wireless is going to deliver amazing capabilities and services. But it won't come cheap. When all is said and done, 5G will cost almost US $1 trillion to deploy over the next half decade. That enormous expense will be borne mostly by network operators, companies like AT&T, China Mobile, Deutsche Telekom, Vodafone, and dozens more around the world that provide cellular service to their customers. Facing such an immense cost, these operators asked a very reasonable question: How can we make this cheaper and more flexible?

Their answer: Make it possible to mix and match network components from different companies, with the goal of fostering more competition and driving down prices. At the same time, they sparked a schism within the industry over how wireless networks should be built. Their opponents—and sometimes begrudging partners—are the handful of telecom-equipment vendors capable of providing the hardware the network operators have been buying and deploying for years.

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