Tree Search Algorithms Applied to the BD-RIS Configuration in MU-MISO Communication Systems

TL;DR

This paper introduces a depth-first tree search algorithm to optimize BD-RIS configurations in MU-MISO systems, balancing performance and computational complexity.

Contribution

It presents a novel tree search method for configuring BD-RIS, enhancing signal reflection adjustments in wireless communication systems.

Findings

The algorithm effectively maximizes channel strength.

It offers a good trade-off between performance and complexity.

The approach is scalable for multi-user systems.

Abstract

The reconfigurable intelligent surface (RIS) has attracted considerable attention of both academia and industry in recent years, given its capacity to dynamically manipulate the reflection of incident electromagnetic waves. Although the research developed for the RIS may have reached its maturity, there are still contentious aspects and limitations regarding its potential benefits for the next generation of wireless communications. In order to improve upon the the RIS technology, the beyond diagonal reconfigurable intelligent surface (BD-RIS) was recently proposed as an promising alternative. The BD-RIS boasts a more sophisticated circuit topology that is capable of providing more combinations of different adjustments or configurations for signal reflection. However, to aptly reap the benefits of the BD-RIS, the added degrees-of-freedom of its configuration must be leveraged accordingly. Therefore, in this work we propose a depth-first tree search algorithm for configuring the BD-RIS in multi-user multiple-input single-output (MU-MISO) communication systems. Taking advantage of the tree search exploration, the proposed algorithm achieves a remarkable trade-off between channel strength maximization performance and computational complexity scalability.