Reconfigurable Intelligent Surfaces in Wireless Communication Systems

The propagation medium in wireless networks has traditionally been regarded as a random and uncontrollable factor that degrades signal quality through scattering, reflection and absorption. Reconfigurable intelligent surfaces (RISs) transform this paradigm by introducing planar arrays of passive or nearly passive elements—meta-atoms—whose electromagnetic response can be tailored in real time. By adjusting phase shifts, amplitude and polarisation of incident radio waves, RISs enable dynamic control of the wavefront without arduous radio-frequency processing, promising enhanced coverage, spectral efficiency and energy savings. These surfaces can be deployed on building facades, indoor walls or surrounding objects to steer signals towards desired users, suppress interference and recycle existing transmissions. Integration with massive multiple-input multiple-output (MIMO) and cell-free architectures leverages RISs to compensate for channel impairments, particularly at high-frequency bands such as millimetre-wave and sub-millimetre-wave. Key challenges include the development of accurate electromagnetic models, low-complexity configuration algorithms, robust channel estimation under limited feedback and scalable control infrastructures. Ongoing research seeks to address these by combining scattering-parameter network analysis, machine-learning-driven optimisation and hardware prototyping, charting a path towards smart radio environments in next-generation wireless systems.

Research from Nature Portfolio

Early investigations have shown that binary-state metasurfaces can passively shape complex microwave fields in reverberating environments. Experiments in typical indoor settings demonstrated that a small electronically tunable surface placed on walls could enhance or cancel transmission between two antennas by an order of magnitude, creating isotropic field distributions without active encoding or decoding. This seminal proof of concept established spatial modulation of existing microwave fields and inspired subsequent advances in passive electromagnetic wave control for communications.

Reconfigurable Intelligent Surfaces in Wireless Communication Systems publication trend

The graph below shows the total number of articles in reconfigurable intelligent surfaces in wireless communication systems across all publications each year (not limited to Nature Index journals).

Technical terms

Reconfigurable intelligent surface (RIS): A planar array of engineered elements whose electromagnetic response can be electronically altered to control incident radio waves.

Metasurface: A two-dimensional structured material composed of subwavelength unit cells that manipulate electromagnetic waves in customised ways.

Phase shift: An adjustment of the phase angle of a wavefront, used to steer or focus radio signals in desired directions.

Beamforming: A signal processing technique that combines elements' outputs to form spatially directed beams towards intended users.

Channel state information (CSI): Knowledge of the propagation characteristics between transmitter and receiver, essential for optimising RIS configurations.

References

1. Shaping complex microwave fields in reverberating media with binary tunable metasurfaces. Scientific Reports (2014).
2. Reconfigurable Intelligent Surface (RIS) in the Sub-6 GHz Band: Design, Implementation, and Real-World Demonstration. IEEE Access (2022).
3. Modeling and Architecture Design of Reconfigurable Intelligent Surfaces Using Scattering Parameter Network Analysis. IEEE Transactions on Wireless Communications (2021).
4. Reconfigurable Intelligent Surface-Assisted Cell-Free Massive MIMO Systems Over Spatially-Correlated Channels. IEEE Transactions on Wireless Communications (2021).