April 1, 2019

Low power consumption technology that enables practical application of 5G

System Platform Research Laboratories
Masaaki Tanio

Masaaki Tanio majored in numerical computation as a university student, and entered NEC in 2009 after earning a master's degree. He has been active on the front lines of research in low power consumption technology for wireless devices, and is developing technology that has received high praise at international conferences.

Leading the world in low power consumption technology for wireless devices

Since entering NEC, I have been engaged in the research of hardware for wireless devices. Specifically, my research theme is signal processing technology that can achieve low power consumption in wireless devices.
For example, the question of how to reduce power consumption in digital terrestrial broadcasting transmitters has become important in terms of both product competitiveness and the environment. However, in the past, the big technological hurdle to overcome was to improve the operational efficiency of power amplifiers, which make up about 80% of the power consumption in transmitters. A dilemma faced by researchers was that when they tried to operate power amplifiers at a high efficiency, distortion occurred in the signal.
In 2015, I developed an algorithm that removed this distortion. This distortion compensation technology can counteract the distortion that occurs when power amplifiers are operated at a high efficiency, thereby leading to a great improvement in power consumption. The technology is now used in actual products in at least 10 countries around the world. In 2018, the patent for this technology also won the Kanto Region Invention Encouragement Award (by Japan Institute of Invention and Innovation).
In addition, my research is in a field that is very relevant to 5G, which is expected to be the communication system of the future. In 5G, it is necessary to perform digital-analog conversion at high speeds in order to increase the communication capacity and broaden the signal bandwidth. A large amount of power is used for this conversion, which is a major issue. I developed 1-bit digital transmission technology that can completely eliminate this digital-analog conversion. The technology generates the signal by replacing the 5G analog signal that requires high-speed and high-voltage resolving power, with an ultra-fast 1-bit digital signal pattern (time axis). This successfully cuts in half the amount of power consumed by the analog wireless circuits other than the power amplifier circuit. This technology has received high praise in academic circles, resulting in its acceptance at seven international conferences, including the International Microwave Symposium (IMS), which is the top conference in the field of microwave technology, as well as five invitations for me to speak as a guest lecturer.

Company support to study overseas

That was the type of research I had been pursuing, and in 2017, I reached a satisfactory level in my work. I thought I wanted to take on the challenge of a new research theme, so for one year starting in October 2017, I made use of the company system and went overseas to study. At NEC, there is a system to support employees for a year of overseas study if they recognize the significance.
I thought I would like to study analog circuit design technology for extremely high frequency waves known as millimeter waves, which will become the mainstream in 5G in the future. However, the general view is that it takes five years to master that technology. I persuaded my superiors that I could master it in one year, so I was given the opportunity to study in the United States.
Of course, studying overseas was terribly difficult (laughter), because I had to learn five years’ worth of cumulated scholarly tasks. I had often reconsidered that my perspective was too narrow, because up to that time I had been devoted only to products. This was a great stimulation to me. In one year, I improved my ability to think with a broader perspective. Before going, I thought one year might not be enough time to study, but it turned out to be just right. Too much time can cause you to lose focus.
Also, there were no financial worries, because the company took care of the tuition and provided support for my living expenses, all while I received a salary. This allowed me to concentrate fully on the research. I think my year studying overseas was a great experience.

Environment that considers the career of each individual researcher

Beyond providing support for studying overseas, NEC thinks about the career of each individual researcher. The company has a culture of managing projects while at the same time considering the viewpoint of cultivating researchers, so that each person's current situation is carefully reviewed when the person is assigned to a project.
Actually, my first three to four years at NEC were a struggle for me (laughter). While entrusted with the development of power amplifiers, I did not produce any results. Honestly, I did not have a very detailed knowledge of wireless technology before entering the company, and I was not familiar with handling hardware, only to damage a variety of equipment. I sometimes felt I had no choice but to resign (laughter).
Although my superiors understood the situation, they considered the educational perspective and allowed the project to continue, and they encouraged me to keep researching until I got a successful experience. In fact, I believe that the experience I accumulated during this period made it possible to eventually produce results for the distortion compensation technology and 1-bit digital transmission technology. Through my experience, I get the strong sense that the company creates an environment where individual researchers are carefully attended to and their careers are taken into consideration.
Looking ahead, I am facing major issues surrounding the commercialization of 5G. I aim to keep working toward solutions by pushing forward with my research and utilizing the knowledge that I gained by studying overseas, as well as the network of contacts that I developed.