Network Systems

Research Staff

  • Prof. Minoru Okada

    Minoru Okada

  • Assoc.Prof. Takeshi Higashino

    Takeshi Higashino

  • Assist.Prof. HOU, Yafei

    Yafei HOU

E-mail { mokada, higa, yfhou }[at]

Research Area

1.Digital TV on Mobile Receivers

In Japan, high-definition television (HDTV) is provided using digital terrestrial television (DTTV) broadcasting. In addition to HDTV, a narrow band digital television service dedicated to handheld terminals, also known as "One-Seg TV", is popular now. After the termination of analog TV services, multimedia broadcasting services have started using the opened VHF analog TV band. However, it is difficult to improve the reliability of reception in mobile and handheld environments. This laboratory is working to develop low power-consumption and reliable handheld digital TV receivers using array antennas and radio signal processing techniques.

2.Mobile Communication Systems

Thanks to recent research and development activities, the bit rate provided by mobile Communication systems, such as cellular systems and wireless local area networks (W-LAN), is growing rapidly. However, its reliability is not good enough for error intolerant purposes, such as surveillance, networked robots, etc. In order to solve this problem, our laboratory studies key technologies including OFDM (Orthogonal Frequency Division Multiplex), MIMO (Multiple Input Multiple Output), diversity, and multi-hop mesh networks. We are working on implementing these technologies onto specific systems such as W-LAN, WiMAX, and Zig-Bee.

3.Radio on Fiber and Distributed Antenna Systems

Recently, different kind of radio wireless and broadcasting systems are available, for example, LTE, WiMAX, mobile multimedia contents broadcasting, etc. The radio on fiber (RoF) is a promising technology for constructing a heterogeneous radio infrastructure. The distributed antenna system (DAS) performs sophisticated radio processing for multi-user, MIMO communication systems.

4.Wireless Sensor Networks

Although radio wave-based sensor systems, such as RADAR and GPS, are capable of measuring positions over a wide area, their function is limited. To enhance their applicability, we are proposing various kinds of sensing networks using radio waves. For example, rain rate estimation using millimeter-wave mesh links, intruder sensing in leaky coaxial cable infrastructure, and positioning sensors for medical applications using RFID tags.

Key Features

We do not only evaluate the systems in theoretical analysis and computer simulation, but also implement ones onto hardware using FPGA (Field Programmable Gate Array) and embedded systems. Students can learn theories on signal processing and communication systems. In addition, they have a chance to experience embedded system programming and digital circuit design.

Fig.1: Research and Development of Highly Reliable Wireless Communication Systems

Fig.1: Research and Development of Highly Reliable Wireless Communication Systems

Fig.2: Container Yard in Tarragona

Fig.2: Container Yard in Tarragona

Fig.3: ESPAR antenna assisted receiver

Fig.3: ESPAR antenna assisted receiver