Exploring Invisible Wireless Communication to Support the Future

You may be viewing this article on your smartphone while on the move. We exchange a variety of information through these palm-sized devices. Cell phones and smartphones are indispensable to modern life, and their smooth communication is the result of research and development. Professor Mamoru Sawahashi of the Faculty of Science and Technology continues his research on fundamental technologies to realize comfortable wireless communications.

Professor Sawahashi’s research focuses on mobile communications, wireless transmission technology for cell phones, and wireless access technology. In particular, he specializes in wireless systems, including mechanisms for increasing frequency utilization efficiency and speed. At first glance, these technologies may seem esoteric, but they can be said to expand and improve the communication “pipes” that allow cell phones and smartphones, which are used daily, to operate smoothly and provide a wide range of services. In recent years, there has been a tendency for academic societies to focus on research into services and applications, but everything is possible only if there is a “pipe” that can let anything pass through it. Steady technological development to make the pipes thicker and sturdier will always be necessary in the future.

Currently, he is mainly conducting research on the “5G” communication standard in collaboration with private companies. One of the advantages of wireless communication is that users can communicate even when they move, but there is also a disadvantage in that moving causes fluctuations in the signals received, resulting in “errors” in communication. In the laboratory where servers are lined up, they are conducting various experiments, such as changing signal frequencies and transmission methods, to elucidate the causes of communication errors. In 2024, Prof. Sawahashi was ranked on a comprehensive list by Stanford University and Elsevier Inc. of the United States that identifies the “top 2% of scientists in the world. The field of telecommunications development is truly ever-evolving. A terminal the size of a refrigerator will fit in the palm of your hand in a few years. Technology is advancing rapidly, so ideas are important. Anyway, you have to read papers and study. Presentations at conferences also require even more novelty.”

The current issue in telecommunications is frequency. The low-frequency band is already almost empty due to increasing traffic (the amount and flow of data sent and received over networks and communication lines within a certain time period). In order to handle the ever-increasing traffic, higher frequency bands must be used. However, there are also issues such as the shorter flying distance of radio waves at higher frequencies, and technological development to solve these issues is urgently needed.
Another issue in high-frequency band communications is “phase noise. If this problem cannot be overcome, the communication service will become unusable. In order to guarantee the communication error that occurs, the software signal processing technology implemented in the terminal needs to be more accurate.
Research is also underway in the area of higher frequencies called the subterahertz band, or so-called “6G. They are working to develop fully guaranteed technology to achieve more reliable and lower latency communications that can be used in industrial applications such as telemedicine and automated driving. In 20 to 30 years, when we enter the world of 6G and 7G, automated driving will be commonplace, and video calls will be possible at a level where people are really right in front of you. In 20 to 30 years, when we enter the world of 6G and 7G, self-driving will be commonplace, and video calls will be so simple that it will be like having a person in front of you. The concept of location will disappear.

Professor Sawahashi was involved in the determination and standardization of 3G and 4G wireless systems at his previous job. As a new employee, he witnessed the development of a shoulder-type car phone that could be carried on the shoulder and taken out of the car. At the time, there were three major radio fields: fixed micro, satellite, and mobile, with mobile being the most minor. Since I was not originally interested in telecommunications, nor had I studied it at university, I did not know the technical terms and spent my days studying hard after joining the company. Then, a TV commercial caught my attention and made me think about the original purpose of telecommunications. It was a TV commercial that said, “You can’t see your parents when they die, but you can hear their voices on your cell phone. Connecting people to people is the best part of telecommunications.”

Telecommunications is a topic of research not only in Japan but also throughout the world. Is there any advantage to researching this field in the city of “Tokyo”? Tokyo is densely populated and has a lot of traffic, even from a global perspective. There are many people on the move. You may have experienced difficulty in getting a signal in Shibuya and other crowded places. It’s a very challenging place to be in this field of research.”
The evolution of communication technology has continued at an accelerating pace since mankind first acquired cell phones and then smart phones. How far will this development go? I have heard that it will continue until the speed of communication reaches the information processing speed of the human brain, and I believe that will be the case. That’s how much information humans want.”
Professor Sawahashi’s attitude toward information is one that he repeatedly conveys to the students in his laboratory. In the future, it will become even more important to select and choose the necessary information from a large amount of information. I want students to think for themselves and face up to what information is important.

More than 30 years ago, cell phones were large enough to be carried on the shoulder. Back then, no one could have imagined the future of smartphones that could fit in the palm of your hand. Today, we are instantly connected to everywhere and can feel the world in the palm of our hand as if by magic. In the near future, there will be a world that we, living in the present, cannot even imagine. However, no matter how much technology evolves, the essence of communication, “connecting people,” will never change. Professor Sawahashi’s gaze looks beyond the invisible radio waves and beyond our daily lives to a more distant and glorious future of communication.