He joined the Communications Research Laboratory (currently the National Institute of Information and Communications Technology, or NICT) under the Ministry of Posts and Telecommunications in 1995. Since then, he has been engaged in the research and development as well as in the standardization of communications technologies in the field of digital signal processing mobile communications, software defined radio, cognitive radio, and wireless smart metering. He was a postdoctoral researcher at Delft University of Technology in the Netherlands from 1996-1997. He served on the board of directors of Wireless Innovation Forum (formerly SDR Forum) , and currently serves on the board of directors of WhiteSpace Alliance, Dynamic Spectrum Alliance and Wi-SUN® Alliance. He is the co-chair of the board of directors of Wi-SUN® Alliance. He is also the chair of the IEEE Dyspan Standards Committee (formerly IEEE 1900) and the vice chair of the Global Alliances as well as the International Standardization Committees of IEEE 802.15.4g, IEEE 1900.4, IEEE 802.15.4m, and TIA TR-51. He has been a professor of the Department of Communications and Computer Engineering of the Graduate School of Informatics of Kyoto University since 2014. He received an achievement award and became a fellow of the IEICE (Institute of Electronics, Information and Communication Engineers) in 2006 and 2009 respectively. He was a recipient of the MEXT (Ministry of Education, Culture, Sports, Science and Technology) Minister’s Award in Science and Technology as well as the MIC (Ministry of Internal Affairs and Communications) Minister’s Award of the Cabinet Office Persons of Merit Award in Industry-Academia-Government Collaboration in 2014.
His research focuses on the fifth-generation mobile communications system, which provides the next-generation wireless broadband networks that connect people. His research also includes the networks connecting a hundred million to a billion things. A challenge in his research is to find and develop new communication methods and protocols that will provide better connectivity to a greater number of people and things. He values collaboration with industry. He clearly defines the roles of industry, and clearly pictures how universities should be. His untiring pragmatic approach in research and development will impact the future of network society.
A Gigabit Data Transmission
Expectations for the 5G Broadband Network
5G, or the fifth-generation mobile communications system, under research and development today is the name given to the next-generation mobile communications standards beyond 4G LTE. The data transmission rate that 5G aims to accomplish in mobile telephone networks is on the order of gigabit, which is a more than hundred- to thousand-fold increase in speed when compared with the standard transmission rate today. The current goal is to launch the new 5G service in 2020, which is not an easy target as it requires efforts in both software and hardware.
The data communication does not always require gigabit data transmission in both uplink and downlink directions. Lower frequency may be used for the transmission of voice, whereas higher frequency may be used for the transmission of gigabit data. There are two kinds of information: control plane (CP) information, which helps the transmission of “information,” and user plane (UP) information, which is the actual contents of the information to be transmitted. While a user is in a lower frequency area, only his or her CP information may be transmitted because the CP information needs traffic for both uplink and downlink. When the user enters a higher frequency area, a volume of UP information may be transmitted using only downlink traffic. This kind of technology that takes advantage of using multiple frequencies is called ultra carrier aggregation. The objective of the research team led by Professor Harada is to find unused spaces in currently used frequency bands, and combine them to accomplish a gigabit data transmission in the aggregate.
Find White Spaces in Frequency Bands and Put Data in Them for Transmission
Technologies that are necessary to realize 5G are one to find white spaces, or unused frequency bands and another to put data in such spaces for transmission. Unused spaces may be scanned using measuring technologies such as a spectrum analyzer, or provided from cloud storage as a database prepared in advance. Information must be sent in an altered form that can be fitted into the spaces. Matching can be accomplished by adjusting the way the frequency range (bandwidth) is occupied by a signal, that is, by changing the signal spectrum. “Either by making hardware filters, or by developing a novel communication method. It will be the best if we have both. The former is a job for device makers like Murata, whereas the latter is a job for universities,” says Professor Harada.
A new approach that has started to produce results since around December 2015 is an application of a communication method called orthogonal frequency-division multiplexing, or OFDM, which smooths out discontinuities between signals by implementing a technique called windowing. This method will allow us to increase data transmission rate easily because the data compression only involves the signal processing. If this is not enough, filters may be introduced. The method will allow us to use the lower frequency range. Since the lower frequency band has a lower data transmission rate, only the data of CP information can be sent. When a user enters the high frequency band area, a large volume of data may be sent using unused bands.
The Fifth-Generation Broadband Mobile Communications System
Two outstanding issues that were not accomplished in 4G should be addressed in 5G. First, further enhancement of broadband mobile communications: more specifically, using four 5 MHz channels in the 4G LTE at most to achieve the maximum data transmission rate of about 300 Mbps for downlink and about 75 Mbps for uplink. Furthermore, bundling 20 of these channels at most to aim at the maximum data transmission rate of 3 Gbps for downlink and 1.5 Gbps for uplink. 5G will require a more than 10 times faster data transmission rate, or a rate on the order of 10 Gbps.
Schematic diagram of the 5G communications system