October 2023 PPCS Meeting - Introduction to Reconfigurable Intelligent Surfaces - with Anders M. Buvarp

#computer#communications#6G#ML#RIS#metasurfaces#Electromagnetic

In addition to machine learning (ML) algorithms, reconfigurable intelligent surfaces (RIS) are considered the key candidates for 6th generation mobile communication systems.

Both technologies introduce a paradigm shift from traditional and contemporary wireless communication methods.

Typically, the wireless channel is considered passive and not modifiable by the network operator; hence, the transmitter and receiver are optimized to overcome fixed impairments of the channel model.

However, with the introduction of RIS, the channel becomes intelligent and controllable to a certain degree.

For example, a mmWave communications system would suffer severely from absorption in the line-of-sight propagation path. Using a RIS for reflecting or directing the electromagnetic wave, the communications link can be properly restored.

Similarly, ML could be used to learn the most effective configuration for particular channel impairments. Remote sensing applications are another area where RIS can assist in enhancing performance.

A RIS is a two-dimensional surface of discrete, individually tunable but passive elements (unit cells), typically consisting of varactors, PIN diodes, or MEMS. Reconfigurable metamaterials and meta-surfaces are another approach to implementing RIS.

By carefully designing and optimizing the tuning of the elements, various electromagnetic (EM) wave transformation objectives can be met.

Some examples of achievable EM functions are polarization, reflection, refraction, focusing, collimation, modulation, absorption, or a combination of these. Furthermore, a RIS can be considered a new type of network node employing structures with various considerations such as form factor, design, and integration.

The RIS has low implementation costs and energy consumption; hence, combining RIS with ML is creating enormous innovation opportunities that will progressively impact the evolution of wireless system architecture, access technologies, and networking protocols.