New model predicts impact of reconfigurable smart surfaces on radio wave propagation

New model predicts impact of reconfigurable smart surfaces on radio wave propagation

An example of RIS. The main beam direction will change when the diodes are changed. Credit: Keisuke Konno

Researchers at Tohoku University, the University of Surrey, and the University of Nottingham have successfully developed a method to analytically express the performance of wireless communication systems when using reconfigurable smart surfaces (RIS).

Think of RIS like mirrors. They are thin surfaces that can redirect the direction in which radio waves propagate. Instead of bouncing randomly, radio waves can be directed purposefully, improving the reliability, strength, and range of a signal. For example, the low diffraction ratio of high-frequency electromagnetic waves can be optimized using RIS.

Because RISs are essentially reflective surfaces that can be placed almost anywhere, they are a more attractive and less costly solution than building entirely new base stations. Accurately modeling the capabilities of RISs is an important first step before they can be widely implemented to improve radio wave signals (such as cell phone service or Wi-Fi).

“RIS is a promising technology, but we need to research them thoroughly before they can be used practically,” explains Keisuke Konno. “As of now, complex, time-consuming, and costly measurements or simulations are required to evaluate the effect of RIS in improving radio wave propagation.”

Numerical results on parametric studies of channel capacity. Full wave: Results obtained by conventional numerical simulation. The results are in perfect agreement with the results of the exact expressions derived in this study. Recommended: Numerical results obtained by approximate expressions derived in this study. Parametric studies were carried out in terms of the location of the receiving antenna rr, and all numerical results are in almost perfect agreement. Source: Keisuke Konno

This is where the model developed by Konno and his team comes in. Several factors predicted by their model matched almost perfectly with those obtained by conventional numerical simulations. According to the derived expressions, the effect of RIS in improving the radio wave propagation environment can be evaluated without resorting to other intensive and costly simulations.

These findings were: published inside IEEE Antennas and Propagation Procedures On June 27, 2024.

To create the model, the research team focused on the fact that the mutual coupling between arbitrarily shaped transmit antennas, receive antennas, and RIS in a wireless communication system can be expressed in the form of an impedance matrix using the method of moments.

First, they decomposed the impedance matrix into block matrices (corresponding to the transmit antenna, the receive antenna, and the RIS). Then, by sequentially solving the matrix equations corresponding to these block matrices, they analytically derived an exact expression for the channel capacity (one of the performance indicators of wireless communication systems).

Using these expressions, the performance of wireless communication systems in the presence of RIS can be easily found. This model can serve as a useful guide to determine the best ways to position RIS so that we can receive stronger wireless signals wherever we are.

More information:
Keisuke Konno et al., Generalized Impedance Model of Wireless Links Supported by Reconfigurable Smart Surfaces, IEEE Antennas and Propagation Procedures (2024). DOI: 10.1109/TAP.2024.3417629

Provided by Tohoku University

Quotation: New model predicts impact of reconfigurable intelligent surfaces on radio wave propagation (2024, July 10) Retrieved July 11, 2024 from

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