3. Use Cases & Applications

Why RIS Applications are Broad

RIS is not a single application. It is a platform technology. Once a surface can shape radio propagation, it can help many wireless tasks: stronger links, lower interference, better localization, improved sensing, and energy-aware coverage.

References for this section3

• E. Basar et al., "Wireless Communications Through Reconfigurable Intelligent Surfaces", IEEE Access, 2019.
• Q. Wu and R. Zhang, "Towards Smart and Reconfigurable Environment", IEEE Communications Magazine, 2020.
• K. M. Faisal and W. Choi, "Machine Learning Approaches for Reconfigurable Intelligent Surfaces: A Survey", IEEE Access, vol. 10, pp. 27343-27367, 2022.

1. Coverage Extension

The most intuitive use is coverage recovery. If a direct path is blocked, an RIS can create a reflected path. This is especially useful at mmWave and sub-THz frequencies, where blockage is severe.

Examples:

• Indoor dead-zone coverage.
• Urban street-canyon links.
• Factory-floor robot connectivity.
• Cell-edge improvement.

References for this section3

• E. Basar et al., "Wireless Communications Through Reconfigurable Intelligent Surfaces", IEEE Access, 2019.
• Q. Wu and R. Zhang, "Towards Smart and Reconfigurable Environment", IEEE Communications Magazine, 2020.
• K. M. Faisal and W. Choi, "Machine Learning Approaches for Reconfigurable Intelligent Surfaces: A Survey", IEEE Access, vol. 10, pp. 27343-27367, 2022.

2. Interference Mitigation

RIS can be configured so reflected interference arrives out of phase with direct interference. It can also steer the desired signal away from unintended receivers.

This does not mean interference disappears everywhere. It means the surface can shape the spatial distribution of energy at selected locations.

References for this section3

• E. Basar et al., "Wireless Communications Through Reconfigurable Intelligent Surfaces", IEEE Access, 2019.
• Q. Wu and R. Zhang, "Towards Smart and Reconfigurable Environment", IEEE Communications Magazine, 2020.
• K. M. Faisal and W. Choi, "Machine Learning Approaches for Reconfigurable Intelligent Surfaces: A Survey", IEEE Access, vol. 10, pp. 27343-27367, 2022.

3. Physical Layer Security

Wireless signals naturally leak. RIS can improve secrecy by:

• Increasing signal strength at the legitimate user.
• Creating weak-signal zones near eavesdroppers.
• Randomizing or shaping propagation paths.

This is particularly attractive when combined with beamforming and artificial noise.

References for this section3

• E. Basar et al., "Wireless Communications Through Reconfigurable Intelligent Surfaces", IEEE Access, 2019.
• Q. Wu and R. Zhang, "Towards Smart and Reconfigurable Environment", IEEE Communications Magazine, 2020.
• K. M. Faisal and W. Choi, "Machine Learning Approaches for Reconfigurable Intelligent Surfaces: A Survey", IEEE Access, vol. 10, pp. 27343-27367, 2022.

4. Localization and Positioning

RIS can act as a known virtual anchor. If the receiver knows the RIS location and estimates the reflected path delay/angle, it can infer position even when the direct path is blocked.

This is one of the strongest research directions for RIS because 6G aims for high-accuracy positioning as a native service.

References for this section3

• E. Basar et al., "Wireless Communications Through Reconfigurable Intelligent Surfaces", IEEE Access, 2019.
• Q. Wu and R. Zhang, "Towards Smart and Reconfigurable Environment", IEEE Communications Magazine, 2020.
• K. M. Faisal and W. Choi, "Machine Learning Approaches for Reconfigurable Intelligent Surfaces: A Survey", IEEE Access, vol. 10, pp. 27343-27367, 2022.

5. Smart Indoor Environments

RIS panels can be placed on walls or ceilings in:

• Hospitals.
• Factories.
• Airports.
• Lecture halls.
• Laboratories.

The goal is to make indoor propagation more predictable. Instead of relying on random wall reflections, the building actively assists communication.

References for this section3

• E. Basar et al., "Wireless Communications Through Reconfigurable Intelligent Surfaces", IEEE Access, 2019.
• Q. Wu and R. Zhang, "Towards Smart and Reconfigurable Environment", IEEE Communications Magazine, 2020.
• K. M. Faisal and W. Choi, "Machine Learning Approaches for Reconfigurable Intelligent Surfaces: A Survey", IEEE Access, vol. 10, pp. 27343-27367, 2022.

6. Wireless Power and Battery-Free IoT

RIS can focus RF energy toward low-power sensors. The energy levels are usually small, but for ultra-low-power IoT nodes, even small improvements can matter.

The practical challenge is that information transfer and power transfer may require different beam patterns.

References for this section3

• E. Basar et al., "Wireless Communications Through Reconfigurable Intelligent Surfaces", IEEE Access, 2019.
• Q. Wu and R. Zhang, "Towards Smart and Reconfigurable Environment", IEEE Communications Magazine, 2020.
• K. M. Faisal and W. Choi, "Machine Learning Approaches for Reconfigurable Intelligent Surfaces: A Survey", IEEE Access, vol. 10, pp. 27343-27367, 2022.

7. Sensing and Environmental Awareness

RIS can help radio sensing by illuminating hidden targets, enhancing weak echoes, or providing an additional geometric viewpoint. This connects directly to RIS-assisted ISAC.

References for this section3

• E. Basar et al., "Wireless Communications Through Reconfigurable Intelligent Surfaces", IEEE Access, 2019.
• Q. Wu and R. Zhang, "Towards Smart and Reconfigurable Environment", IEEE Communications Magazine, 2020.
• K. M. Faisal and W. Choi, "Machine Learning Approaches for Reconfigurable Intelligent Surfaces: A Survey", IEEE Access, vol. 10, pp. 27343-27367, 2022.

Application Selection Guide

Problem	RIS role
Blocked user	Create virtual LoS
Strong interference	Create spatial nulls or redirect energy
Weak localization geometry	Add virtual anchor
Indoor mmWave coverage	Smart wall/ceiling reflection
Low-power sensor	Focus RF energy
Hidden target sensing	Provide NLoS illumination path

References for this section3

• E. Basar et al., "Wireless Communications Through Reconfigurable Intelligent Surfaces", IEEE Access, 2019.
• Q. Wu and R. Zhang, "Towards Smart and Reconfigurable Environment", IEEE Communications Magazine, 2020.
• K. M. Faisal and W. Choi, "Machine Learning Approaches for Reconfigurable Intelligent Surfaces: A Survey", IEEE Access, vol. 10, pp. 27343-27367, 2022.

Takeaway

RIS is useful when controlling propagation is cheaper, greener, or more practical than adding another active base station. Its strongest applications appear in blockage-prone high-frequency systems, localization, and joint communication-sensing networks.

References for this section3

• E. Basar et al., "Wireless Communications Through Reconfigurable Intelligent Surfaces", IEEE Access, 2019.
• Q. Wu and R. Zhang, "Towards Smart and Reconfigurable Environment", IEEE Communications Magazine, 2020.
• K. M. Faisal and W. Choi, "Machine Learning Approaches for Reconfigurable Intelligent Surfaces: A Survey", IEEE Access, vol. 10, pp. 27343-27367, 2022.