Graduate School of Science and Engineering Electrical and Electronic Engineering

Communication Systems Laboratory

Website of the Laboratory 【In Japanese】

Wireless Communications Shaping the Dream of Future Society

Staff

Research Topics

• Next generation mobile communications system/transmission technologies
• Radio wave propagation in wireless communications

Research Contents

Communication systems laboratory conducts education and research in the field of wireless communication systems as well as radio wave propagation. Our mission is to contribute to the realization of future wireless communications. Researches on these research topics are carried out by investigating novel methods and technologies and evaluating their effectiveness with computer simulations and indoor/outdoor wireless experiments.

Our major research themes are the technologies in the fields of mobile communications and other wireless communications described below.

<1> Next generation mobile communications system/technology

In the mobile communications field, in continuation of the first generation (1G) analog automobile telephone system, the second generation (2G) early digital mobile communications system, and the third generation (3G) and the fourth generation (4G) communications system advanced in high speeds and international standards, currently research and development of the so-called fifth generation (5G) and beyond 5G (B5G) of the mobile communications system is moving forward. From the 5G system, instead of a concept where a single large system comprehensively supports the entire environment and services, a concept where heterogeneous systems are split up according to the usage environment or application, for example cellular communications to cover wide areas and wireless LANs suited to high-speed transmissions, is envisioned. A large increase in transmission capacity is also necessary with the personalization and ambience of wireless communications. The implementation of broadband transmissions is a fundamental technological challenge even in 5G and B5G. As is symbolized by the expression "anywhere, anytime, and with anything," a major issue is also implementing technologies so as to provide easy-to-use and user-friendly communications at low prices.
For these problems, our laboratory is researching and developing next generation wireless transmission technologies. Research on the next generation wireless transmission technologies is fundamental research about how to conduct broadband wireless transmissions within limited frequency resources on the basis of statistical behavior of wireless channels. Specifically, broadband single-carrier, OFDM, MIMO, and other topics are our research subjects. For these methods we are formulating new technologies, qualitatively evaluating their performance by computer simulations and verifying their effectiveness with the aid of software-defined radio transceiver.

<2> Radio wave propagation, measurement technology in wireless communications

When thinking about cellular systems, for example, the installation location of base stations and as a result deciding how many base stations to install is a major issue in constructing cellular networks. In other words, there are problems such as dead zones where radio waves do not reach, making the supply of communications impossible, if the distance between base stations is too large, but on the other hand if base stations are densely installed, the dead zones are reduced but the cost of wireless network infrastructure construction increases. To resolve these issues, it is important to establish propagation models to precisely estimate propagation characteristics such as propagation loss, multipath delay and so on in radio channels. In this way, it is possible to design an optimal wireless network. In recent years, many forms of wireless communications have been developed such as wireless LAN for local communications and UWB and RF-ID for short distance communications. It is also important to construct propagation models for respective environments to establish these systems. In our laboratory we are researching these propagation models.
The research technique in our laboratory is mainly computer simulations, but eventually the evaluation and verification of wireless communications by wireless experiments using radio waves is necessary. For this we are also working on investigating and developing wireless experimentation techniques. For example, in an environment where interference exists, performance evaluations are conducted with actual radio waves emitted for the technologies developed in the laboratory, our private key sharing method for example, and along with research on those evaluation technologies, the effectiveness of the formulated technology is verified.

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