Programmable radio waves promise better wireless networks

Institute of Technological Innovation

Programmable radio waves promise better wireless networks

Wireless researchers have recently begun studying a new type of device that passively reflects radio waves, called a reconfigurable intelligent surface (RIS).

The new mirrors allow us to push the limits of wireless channel capacity established in 1948 by Shannon. They will be at the heart of all new advances in wireless communications.

– Teacher. Merouane Debbah, Chief Researcher, AI and Telecommunications Systems

ABU DHABI, UNITED ARAB EMIRATES, Dec. 27, 2021 / — When there is a wireless dead spot in a home, office or shopping mall, the most common solution is to replace or move the antenna to the base station/access point, telephone or network. Another approach is to add a repeater or mesh network, which can extend the range, but these require a constant power source and could even slow down communications.

Wireless researchers have recently begun studying a new type of device that passively reflects radio waves called a reconfigurable intelligent surface (RIS). Eventually, these could help eliminate dead zones while using less power and providing better performance than wireless repeaters. Researchers have figured out how to install a few under controlled circumstances, but haven’t explored how a fleet of RISs in a larger facility, such as a factory or office, might improve wireless communications.

Today, research from the Technology Innovation Institute’s [TII] The Artificial Intelligence and Telecommunications Systems Research Group, led by Chief Researcher Professor Merouane Debbah, in collaboration with other institutions, is developing new tools to understand the performance of wave propagation environments smart radios enabled by multiple RIS devices working in concert.

George C. Alexandropoulos, assistant professor at the National and Kapodistrian University of Athens (University of Athens), who is working on the project, explained: “Beyond 5G, networks face many challenges to To achieve faster data rates, lower latency and massive device connectivity, RIS technology could help us densify wireless networks in an energy and cost efficient way.

New mirrors

Traditionally, wireless engineers have focused on improving transmitters and receivers. RIS promises a way to improve wireless support itself. “This provides additional degrees of design freedom for communication theorists and communication systems engineers,” said Professor Alexandropoulos.

Each RIS is a thin panel, currently the size of a window, made up of many tiny, controllable reflectors that can effectively impact the propagation of radio signals at will. Each RIS-based mirror in the set can be individually steered to optimize reflection for a given environment or signal wavelength (the trend for future 6G networks is in the terahertz bands). It can react to changes, such as the movement of people, objects, phones or computers in space.

One of the main challenges is figuring out how to make a collection of them work together effectively.
“They include very low-power basic circuitry to adjust their reflective elements and cannot perform any form of sophisticated processing like conventional transmitters or receivers,” Professor Alexandropoulos explained. In some ways, it’s like the difference between a Kindle screen’s programmable ink that can last for weeks because it only requires power to change pages, versus an always-on iPad that runs out. in one day.

This low power consumption means that a RIS could be recharged by a small solar cell which converts light into electricity. “The new mirrors allow us to push the limits of wireless channel capacity established in 1948 by Shannon. They will be at the heart of all new advances in wireless communications,” said Professor Debbah.

Tune together

Some research has focused on how to build them more efficiently. Other research has explored finding better ways to detect and respond to changes in the radio environment. But most of that work has focused on each individual device. The TII collaboration has developed new mathematical tools to help understand how a collection of RISs might work together more efficiently and what are the ultimate performance limits they can offer.

“At TII, we are inventing the future of wireless communications. This joint work provides the basis for a framework to define next-generation wireless communications. We are excited to see these new ideas come to fruition,” said Professor Debbah.

One of the first results was a way to more efficiently compute mutual ergodic information to analyze the performance gains of multiple SRIs. This is a well-established metric for communications systems, but it was not possible to calculate for RIS wireless communications with existing tools.

Another innovation was a new algorithm to optimize the RIS configuration in response to slower summaries of signal characteristics, rather than real-time signal strengths. This means that the RIS has to make fewer adjustments to get good results, thus reducing power consumption.

“Until now, people were considering optimizations that took more computational time and effort while requiring expensive knowledge to gain knowledge about the wireless medium,” Professor Alexandropoulos said.

The researchers were also able to determine the best way to optimize signals coming from different directions. Specifically, if there are a lot of reflections in a room, there is less need to constantly redirect the reflectors, random configurations of the RISs at each instant will do the trick on average.

The team hopes to inspire further research and collaboration on the best ways to improve wireless infrastructure using large numbers of passive reflectors. In the meantime, having a better model for RIS lays the foundation for scaling the technology for larger environments and new use cases. “These tools provide the basis for statistically characterizing the data throughput achievable with a collection of RIS,” said Professor Alexandropoulos.

Tania Ameer
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