For the past several decades, the wireless environment was all about using electromagnetic waves to transmit information without an electrical conductor as a medium. Now the effort is on to go beyond and actually control the direction of wireless signals for enhanced communication, with the aid of reconfigurable intelligent surfaces (RIS).

An RIS is a planar surface composed of “scattering elements” engineered to control the movement of electromagnetic waves between transmitters and receivers toward specified directions—such as around a corner of a building corridor or across multiple floors—eliminating interference, said Marco Di Renzo, a CNRS research director with the Laboratory of Signals and Systems (L2S) of Paris-Saclay University in France.

A controller device connected to the planar surface dynamically adjusts the phase shifts and the amplitudes of all the scattering elements to control the wave movements through signal reflections, refractions, focusing, collimation, modulation and their combinations.

“An RIS can be implemented using mostly passive elements, without requiring high-cost active components, such as power amplifiers, thus possibly resulting in a low implementation cost and energy consumption,” Di Renzo said. “An RIS is not expected to possess sophisticated signal processing capabilities, but only the necessary low-power electronic circuits for enabling its reconfigurability and hence controlling the propagation environments.”

This may result in an easier and more flexible deployment, and RIS-equipped nodes may be able to take any shape and even be integrated onto objects such as walls, buildings, lamp posts and indoor and outdoor advertising on street furniture, he said.

“Thanks to these features, an RIS is often referred to as a ‘nearly passive’ device, and hence it is unlikely to increase the exposure to electromagnetic fields,” Di Renzo said. “These associated characteristics suggest that an RIS may be considered as a sustainable and environmentally friendly technology solution.”

RIS use cases, deployment scenarios and requirements are spelled out in a May 2023 report published by the European Telecommunications Standards Institute (ETSI).

“[RIS] is a new type of network that does not transmit or receive the way other solutions do—it essentially manipulates signals on an electromagnetic surface through reflection, absorption or refraction, or through a combination of them. Think of it as a smart mirror.” —Arman Shojaeifard

“This is a new type of network that does not transmit or receive the way other solutions do—it essentially manipulates signals on an electromagnetic surface through reflection, absorption or refraction, or through a combination of them. Think of it as a smart mirror,” said Arman Shojaeifard, chair of ETSI’s Industry Specification Group on RIS. RIS can serve as a new low-cost, energy-efficient deployment solution for enhancing coverage performance in 5G-Advanced and future 6G systems by intently reflecting signals to and from the end users, he said.

“Because there is no transmitting or receiving, ultimately RIS can lower the cost and complexity of communication, and be more energy efficient,” he said.

RIS applications in healthcare

One potential use case for RIS is for contactless patient monitoring, said Qammer H. Abbasi, professor of applied electromagnetics and sensing at the University of Glasgow’s James Watt School of Engineering in Scotland.

Abbasi and his team have conducted research on intelligent surfaces embedded with an array of miniature elements, such as antennas or sensors, that can be strategically placed on walls, ceilings or floors, forming an intelligent infrastructure throughout the space where a patient resides.

“By manipulating the reflection, absorption and redirection of electromagnetic waves, RIS can capture and analyze physiological data from patients without direct contact,” Abbasi said in an interview. “The RIS panels can detect vital signs, movement patterns, respiratory activity and even gestures or falls, depending on the sensors deployed.”

The collected data is wirelessly transmitted to monitoring systems or healthcare providers, enabling real-time analysis, remote diagnostics and timely interventions, he said.

The benefits of RIS for contactless patient monitoring are multifold, Abbasi said:

• Enhanced patient comfort and safety: RIS enables noninvasive monitoring, eliminating the need for physical connections, wires or sensors attached to the patient’s body. This enhances patient comfort and reduces the risk of infections, discomfort or injuries associated with traditional monitoring methods.
• Continuous and remote monitoring: RIS enables continuous and remote monitoring of patients, even in their own homes. Healthcare providers can receive real-time data and promptly respond to critical situations or changes in the patient’s condition, allowing for proactive interventions and reducing the need for frequent hospital visits.
• Privacy and dignity: With RIS, patient monitoring can be conducted discreetly, preserving the privacy and dignity of individuals. Unlike camera-based surveillance, RIS focuses on capturing physiological data without capturing identifiable visual information.
• Improved accuracy and reliability: RIS technology allows for precise measurements and data collection due to its close proximity to patients. The ability to control and manipulate electromagnetic waves improves the signal quality, minimizing noise and interference, which leads to more accurate and reliable data.
• Scalability and flexibility: RIS can be easily scaled and adapted to various room sizes, layouts and building structures. Electrical contractors can install and configure RIS panels according to specific monitoring requirements, providing flexible and customizable solutions.
• Energy efficiency: RIS panels can optimize energy consumption by actively managing the transmission and reflection of electromagnetic waves. This helps prolong the battery life of wireless sensors and reduces overall energy consumption, aligning with sustainable and cost-effective practices.

With each use case described in the report, the group also identifies KPIs, deployment scenarios and potential requirements to enable interoperability with existing and upcoming wireless technologies and networks.

“In the future 5G-Advanced and 6G wireless networks, many new applications, such as in eHealth, strongly impose requirements on both the communication and sensing performance,” Shojaeifard said. “As an example, a RIS can reconfigure the radio environment to sense human posture and detect someone falling, a useful application for elderly care.”

In July, ETSI released another report by the group that details the various communication models that offer a trade-off between electromagnetic accuracy and simplicity for performance evaluation and optimization. The report also analyzes channel models that include path-loss and multipath propagation effects and the impact of interference.

KPIs are also outlined in the report, as well as the methodology for evaluating the performance of RIS for its application to wireless communications—including the coexistence between different network operators—and for comparing transmission techniques, communication protocols and network deployments.

Opportunities for ECs

For electrical contractors considering doing business in this emerging field, Abbasi recommends collaborating with healthcare providers, RIS manufacturers and other stakeholders to understand specific monitoring requirements and how to integrate RIS technology effectively into homes and facilities.

“Electrical contractors should evaluate the electrical and networking infrastructure requirements to support the installation and operation of RIS panels,” he said. “Consider power supply, data connectivity and compatibility with existing systems.”

It’s important for electrical contractors to stay informed about relevant regulations and compliance standards related to patient monitoring and data privacy to ensure that the installations adhere to legal requirements, Abbasi said.

“They should also provide training to end-users, caregivers and facility staff regarding the operation and maintenance of RIS systems—and offer ongoing support to address any technical issues or upgrades,” he said.

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