TECH

Stacked intelligent surfaces could boost wireless reliability and security for 6G

Wireless communication is about to get stronger, clearer, and more secure, thanks to a new idea from UBC Okanagan researchers. Dr. Anas Chaaban and his team in the School of Engineering are exploring a method to improve the way stacked intelligent surfaces (SIS) can process electromagnetic waves more efficiently.

How stacked intelligent surfaces work...SIS is an emerging alternative to conventional wireless hardware, Dr. Chaaban says, as layers of specially engineered materials are used to directly manipulate electromagnetic waves.

"Electromagnetic waves travel through special surfaces that consist of several elements. These elements mimic neurons in a computerized neural network," Dr. Chaaban says. "As the waves move through the surface, each element changes them slightly. When the waves come out, they are captured by antennas that send the signals to digital processors for further analysis."

Unlike traditional systems that rely on complex and power-hungry circuitry, SIS technology enables fast, low-energy signal processing by controlling how signals propagate through space.

Adding nonlinear intelligence to signals...This new research, published recently in IEEE Wireless Communications, introduces a nonlinear architecture, enabling these surfaces to behave more like artificial neural networks. By incorporating nonlinear behavior into each element, the system can process signals in more complex ways—similar to how modern AI systems handle data.

Until now, most SIS designs have relied on linear operations, so they could only perform relatively simple signal transformations. As a result, these designs cannot take full advantage of advanced communication techniques.

"Nonlinearity unlocks a fundamentally new capability for intelligent surfaces, allowing them to perform tasks that linear systems simply cannot achieve," says Omran Abbas, who is the study's co-author and a UBCO doctoral student.

The idea of using an SIS in this way is not new, he adds, but by using the nonlinear elements, the system can have more intelligence to perform AI-like operations. In a simulated wireless system, the nonlinear system demonstrated improved communication reliability, reducing symbol error rates compared to conventional designs. The improvement comes from the surface's ability to create complex wave patterns that are more resilient to noise and interference.

From prototype design to future networks...Dr. Loïc Markley, a co-investigator on the project with a background in periodic structures and metamaterials, says they are working on the physical design of a non-linear unit cell to build a prototype.

"We are very excited to design a system that incorporates non-linear responses so we can test our theoretical predictions in a real-world environment," he says.

Dr. Chaaban adds that beyond performance gains, the technology also shows promise for enhanced wireless security as these non-linear transformations are characteristically harder to predict and harder for unintended receivers to intercept or decode signals.

Although more research is needed to validate real-world deployments, the findings highlight the untapped potential of non-linear intelligent surfaces as a powerful new tool for next-generation communication systems.

"This innovation could play a key role in enabling future wireless technologies, including 6G communications," Dr. Chaaban says.

"We are analyzing the ideas and investigating them further, and we are also working on testing a nonlinear SIS. This technology could significantly improve reliability, efficiency, and security in next-generation networks."

The use of Stacked Intelligent Metasurfaces (SIMs) can significantly increase the reliability and security of 6G wireless networks.

Unlike conventional single-layer intelligent surfaces (RISs), SIMs utilize multiple layers of programmable materials arranged in a cascaded fashion. This volumetric architecture allows for much more precise control of electromagnetic waves, functioning as a kind of electromagnetic neural network processed directly in space, even before the signal reaches the digital circuits.

How SIMs improve reliability... Stacked surfaces increase network stability through:

-High-precision beamforming: Unlike simple RISs that only reflect waves, SIMs perform spatial filtering and near-field focusing, creating narrower and more directed beams that drastically reduce interference between users.

-Noise resilience: Recent research shows that non-linear SIM architectures can generate complex wave patterns that are more resistant to noise and external interference than traditional systems.

-Error reduction: In 6G system simulations, SIM models demonstrated a significant reduction in symbol error rate (SER), ensuring that information reaches its destination more clearly.

How SIMs Enhance Security: In 6G, physical layer security is enhanced by SIMs due to their inherent complexity:

-Interception Difficulty: The non-linear transformations applied to the signal by the stacked layers are extremely difficult to predict. This makes it nearly impossible for an unauthorized receiver (such as an eavesdropper) to intercept or decode the message.

-Eavesdropping Suppression: SIMs can be configured to maximize the signal on the legitimate user while creating "silent zones" or destructive interference in locating potential intruders, increasing the network's so-called secrecy capability.

Provided by University of British Columbia