Network Systems

Research Staff

  • Prof. Minoru Okada

    Prof.
    Minoru Okada

  • Assoc.Prof. Takeshi Higashino

    Assoc.Prof.
    Takeshi Higashino

  • Assist.Prof. Duong Quang Thang

    Assist.Prof.
    Duong Quang Thang

E-mail { mokada, higa, thang }[at] is.naist.jp

Research Area

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, known as "One-Seg TV", is popular now. After the termination of analog TV services, multimedia broadcasting services have started using the vacated VHF analog TV band. However, it is difficult to improve reception reliability in mobile and handheld environments. This laboratory is working on developing low power-consumption and reliable handheld digital TV receivers using array antennas and radio signal processing techniques.

Mobile communication systems

With recent research and development activities, the bit rate of mobile communication systems, such as cellular systems and wireless local area networks (W-LAN), is increasing rapidly. However, its reliability is not satisfactory 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 multihop mesh networks. We are working on implementing these technologies into specific systems such as W-LAN, WiMAX, and Zig-Bee.

Radio on fiber and distributed antenna systems

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

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 propose 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.

Wireless power transfer

There has been an increasing demand for wireless power transfer (WPT) for mobile nodes. Although many WPT systems have been developed and are widely used, it is difficult to transfer power to moving nodes using WPT. In conventional WPT using electromagnetic coupling, the distance between the transmitter and receiver is limited to few tens of centimeters. The motion of the power reception nodes leads to a decrease in the power transfer efficiency due to impedance mismatching.
Network Systems Laboratory is now working on developing a wide-area WPT system using a parallel feeder line. This system is capable of accommodating mobile receiving nodes including vehicles.

Key Features

We do not only evaluate systems through theoretical analysis and computer simulation, but also implement them onto hardware using FPGA (Field Programmable Gate Array) and embedded systems. Students learn theories of signal processing and communication systems. In addition, they experience embedded system programming and digital circuit design.

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

Fig.1: Highly reliable wireless communication system research and development

Fig.2: Container Yard in Tarragona

Fig.2: Wireless sensor network container yard in Tarragona

Fig.3: ESPAR antenna assisted receiver

Fig.3: ESPAR antenna assisted receiver