The use of higher frequency bands such as millimeter wave and terahertz bands is being considered for 5G-Advanced and 6G. Millimeter-waves have strong linearity, and the challenge is how to cover out-of-sight areas. In recent years, studies have been conducted on Reconfigurable Intelligent Surfaces (RIS) that dynamically control the radio propagation environment. The terahertz band has a wide bandwidth, and its use as a high-resolution sensor is also being considered. In this workshop, we invited researchers and engineers who are actively working on the use of high-frequency bands in 5G-Advanced and 6G, and discussed the latest trends and issues in their research and development.

Dr. Satoshi Suyama (NTT DoCoMo, Inc.) explained about his company's case studies of millimeter wave and sub-terahertz wave applications. He mentioned that coverage improvement technology in high-frequency band, inter-node transmission technology, and wireless relay technology have advanced to the proof of concept level, and introduced in-factory transmission experiments and actual measurements of sub-THz band radio propagation characteristics. He also explained the development status of the system level simulator for 6G with demonstration movies.

Dr. Yuichi Kawamoto (Tohoku University) explained the beam formation method and characteristics of the Intelligent Reflecting Surface (IRS), which is a passive reflective surface that can adjust the reflection phase of radio waves, through evaluation experiments of a 60 GHz band prototype and a static reflector made of transparent reflective film. We discussed other theoretical considerations and future issues.

Mr. Akinori Taira (Mitsubishi Electric Corporation) gave a lecture on sensing systems utilizing the characteristics of terahertz waves. He explained, with many experimental results, that the short wavelength of terahertz waves has the property of transmitting through objects, and that by observing and analyzing the reflected waves, internal structures can be imaged nondestructively and with high precision. In addition, issues for motion detection and implementation were discussed.

All three lectures were at the stage where ｐroof of concept can be conducted, indicating that the efforts toward the practical application of millimeter wave and terahertz wave have made great progress. The participants deepened their understanding of the issues and future prospects for industrial applications of wireless communications, and had lively discussions. The workshop was very useful to learn about research and development trends of millimeter wave and terahertz bands in 5G-Advanced and 6G, and to share future issues with the participants.