Every time we make a video call, stream a movie, or sync smart devices, wireless signals bounce through walls, buildings, cars, trees, and even people. Along this chaotic journey, the signal reaches us through multiple paths—some strong, some weak, some delayed, some distorted. This phenomenon, known as multipath fading, often leads to signal degradation and unreliable connectivity.

For decades, wireless engineers have focused on making transmitters smarter, receivers more sensitive, antennas more optimized, and software more intelligent. But what if, instead of only improving these endpoints, we could actively control the space between them? What if buildings and walls were designed not to block signals, but to help transmit them?

This transformative idea is what gave rise to Reconfigurable Intelligent Surfaces (RIS), a groundbreaking technology aimed at turning the radio environment into a controllable asset rather than a random obstacle.

What is a Reconfigurable Intelligent Surface (RIS)?

A Reconfigurable Intelligent Surface is a software controlled electromagnetic structure that can dynamically influence how radio waves propagate in a wireless environment. RIS can be thought of as “smart wallpaper” or a digitally responsive surface installed on walls, building exteriors, poles, or indoor infrastructure to intentionally reflect or guide wireless signals.

Instead of allowing signals to scatter randomly, Reconfigurable Intelligent Surfaces (RIS) adaptively shape electromagnetic wave propagation to optimize wireless communication. By steering signals toward intended receivers, reinforcing weak links, and reducing unnecessary interference, RIS enables coverage and reliability improvements without introducing new active transmission points, making it an attractive complement to traditional network densification.

Engineering Realization of RIS
RIS can be realized using a range of electromagnetic structures, depending on performance goals, cost targets, and deployment constraints.
Common engineering approaches include:

• Patch array based designs, using conventional RF substrates and electronically tunable elements
• Metasurface inspired designs, often explored in research and early product prototypes
• Hybrid approaches, combining antenna, surface, and control plane innovations

While metasurface based designs are prominent in academic literature, many practical RIS deployments favor simpler, well understood RF materials and architectures, as these improve manufacturability, scalability, and long term reliability—key factors for outdoor and large area installations.
Across implementations, most RIS architectures are passive or quasi passive, requiring power only for sensing, control, and reconfiguration. Since the surface itself does not amplify RF signals, this approach keeps energy usage extremely low while avoiding noise amplification.

RIS Category

Structural Design
RIS can be realized using multiple structural approaches, including:

• Patch array based RIS: Derived from conventional antenna engineering, offering a practical balance of performance, cost, and design maturity
• Metamaterial or metasurface inspired RIS: Enables fine grained electromagnetic control, often at the expense of increased design and fabrication complexity

The choice of structure depends on frequency band, deployment environment, coverage objective, and economic constraints, rather than a one size fits all solution.

Energy Consumption and Operational Nature
RIS can also be categorized by their power characteristics:

• Passive lossy: Very low energy consumption with some insertion loss
• Passive optimized: Designed to minimize losses while remaining non amplifying
• Active RIS: Uses amplification to compensate losses, trading energy efficiency for performance

For most operator use cases, passive or passive optimized RIS architectures offer the best trade off, as they preserve RIS’s core advantage—improving coverage without adding new energy hungry network elements.

How Reconfigurable Intelligent Surfaces Work

Reconfigurable Intelligent Surfaces operate through three primary mechanisms:

• Reflection: Acting like a smart mirror, RIS can redirect incoming signals toward desired directions instead of letting them scatter randomly. This controlled reflection improves signal strength and coverage in targeted areas.
• Refraction: Similar to bending light through a prism, RIS can alter the path of wireless signals to reach blind spots or areas with poor connectivity. By refracting signals, RIS ensures that even hard-to-reach locations receive reliable coverage.
• Waveguiding: Beyond simple reflection or refraction, RIS can internally route electromagnetic waves across its surface before transmitting them outward. This capability allows for precise control over how and where signals emerge, optimizing network performance.

Why RIS Matters to Operators: CAPEX and OPEX Perspective

From an operator standpoint, RIS is valuable not because of how it is built, but because of what it avoids.
Unlike deploying additional radios, repeaters, or small cells, RIS:

• Requires no additional spectrum
• Introduces no new baseband or RF transmission chains
• Consumes only marginal power for control functions
• Adds minimal ongoing operational complexity

By intelligently reshaping propagation, RIS allows operators to improve coverage and quality of experience using the existing network, helping reduce both capital investment and long term energy and maintenance costs. This economic efficiency is a central driver behind growing industry interest in RIS for 5G Advanced and future 6G networks.

Key Functionalities of RIS

Reconfigurable Intelligent Surfaces go far beyond simple signal redirection. Features such as anomalous reflection and dynamic beam focusing enable unprecedented control over the propagation environment, paving the way for highly efficient, adaptive, and intelligent networks.

• Anomalous Reflection: Traditional surfaces reflect waves at predictable angles based on the laws of physics. RIS breaks this limitation by engineering reflections at customized angles, enabling signals to bend in directions that maximize coverage and efficiency. This “smart bending” is crucial for overcoming obstacles and delivering connectivity where conventional methods fail.


• Beam Focusing: Imagine speaking in a crowded room—if you whisper directly to one person instead of shouting to everyone, your message is clearer and more efficient. Beam focusing works on the same principle. RIS converges electromagnetic energy toward a specific point, ensuring that users in weak-signal zones receive strong, reliable connectivity without wasting power on unnecessary broadcasts.

Advantages of RIS

• Highly Deployable: These panels can be seamlessly integrated into a wide range of environments, including building facades, indoor walls, roadside infrastructure, UAV wings, and even smart wearables. This adaptability makes RIS an ideal solution for enhancing connectivity in both urban and remote areas without requiring extensive structural changes.


• Boosts Network Performance: RIS technology significantly improves network performance by creating virtual line-of-sight paths between base stations and end-users. This capability is particularly valuable in dense urban environments where physical obstructions often degrade signal quality. By intelligently redirecting signals, RIS ensures stronger, more reliable connections, reducing dead zones and enhancing user experience.


• Sustainable and Energy Efficient: Unlike traditional repeaters, RIS does not amplify signals or generate additional noise. Instead, it enhances signal propagation organically by manipulating the wireless environment. This passive approach makes RIS inherently energy-efficient and environmentally friendly, contributing to sustainable network deployments without compromising performance.


• Infrastructure Compatible: RIS technology is designed to complement existing communication systems rather than replace them. It works seamlessly alongside Wi-Fi, 4G, 5G, and even future 6G networks, making it a cost-effective upgrade for operators. This compatibility ensures that RIS can be integrated into current infrastructure with minimal disruption, accelerating the transition to next-generation connectivity.

Application of RIS

• RIS in Cellular Networks: By intelligently shaping the wireless environment, RIS can improve coverage, strengthens connectivity in weak signal zones, and optimizes handover efficiency between cells. Additionally, RIS boosts mobile edge computing performance by improving the wireless link quality between users and nearby edge servers, which is critical for latency-sensitive applications.


• RIS in Indoor Systems: Indoor environments often suffer from signal blind spots caused by physical obstructions and complex layouts. RIS addresses this challenge by dynamically redirecting signals to eliminate coverage gaps. From corporate offices and shopping malls to stadiums and smart homes, RIS ensures seamless connectivity, delivering a superior user experience in high-density indoor spaces.


• RIS in Smart Cities and Autonomous Systems: In smart cities, RIS technology enhances support for autonomous and unmanned systems by intelligently reshaping the wireless environment to create reliable virtual communication pathways. By redirecting and strengthening signals around buildings and urban obstacles, RIS reduces the need for UAVs to reposition themselves solely to maintain connectivity. This minimizes drone movement, lowers energy consumption, and extends operational time. At the same time, RIS ensures stable and low latency communication, which is essential for critical applications such as traffic monitoring, emergency response, and urban logistics—making city scale automation more efficient, reliable, and sustainable.


• RIS in IoT and Industry 4.0: RIS strengthens communication between sensors and devices in IoT-driven ecosystems. Whether it’s smart agriculture, automated factories, warehouse management, or environmental monitoring, RIS enhances signal reliability and coverage, enabling real-time data exchange. This capability is essential for Industry 4.0, where uninterrupted connectivity drives automation and operational efficiency.


• RIS in 6G Networks: RIS is expected to become a cornerstone of 6G networks, enabling programmable wireless environments that adapt dynamically to user and application needs. By operating passively and efficiently, RIS contributes to sustainable network architectures while delivering ultra-high reliability and performance. Its integration into 6G will redefine connectivity standards for the next decade.

Industry Direction and Ongoing Work

RIS is an active area of research and development across industry and academia, with multiple vendors and institutions exploring different realizations, control architectures, and deployment models.
Tejas Networks is actively developing Reconfigurable Intelligent Surface (RIS) technology as part of its 5G Advanced and 6G roadmap. The company has demonstrated working RIS hardware in the 3.5 GHz band at India Mobile Congress 2025, integrated with massive MIMO for coverage enhancement. Tejas is also collaborating with COMET Foundation (Technology developed by IIT-Bhilai , IIT-Jodhpur and IIIT-Bangalore) to develop prototype RIS systems and is working on RIS controller architectures for future 6G networks. While RIS is not yet commercially deployed, Tejas is positioning it as a key infrastructure element for coverage extension, energy efficiency, and intelligent radio environments in next generation networks.
RIS represents a shift in how wireless networks are engineered—moving beyond smarter transmitters and receivers toward smarter environments. By focusing on practical, cost effective engineering choices, RIS has the potential to become a scalable tool for operators, turning once passive surfaces into active contributors to network performance.

References:

• https://arxiv.org/pdf/2007.03435
• https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=8796365