- High-speed Communication by Automatic Utilization of Available White Spaces -

The National Institute of Information and Communications Technology (NICT) has developed the world's first portable-size tablet terminal that enables IEEE802.11-based radio communication in TV bands (470-710 MHz). This tablet terminal utilizes a WLAN system for radio communication in TV bands with an inquiry in the white-space database developed by NICT. The original 2.4 GHz band of a WLAN system is also available and it is possible that the tablet terminal automatically selects the radio communication band according to data traffic, etc. through control by the network manager. The white-space utilization by portable devices achieves not only fixed-point communication but also mobile communication, and contributes to the further effective use of frequency resources.

Background

Due to the explosive growth of mobile portable devices such as smartphones and tablet terminals, communication traffic has been increasing and a frequency resource shortage problem has been aggravating. To solve this problem, utilization of TV white spaces is studied and the establishment of radio rules designed for TV white-space operation has been started in the U.S., the U.K., etc. NICT has contributed to standardization on various radio communication systems utilizing TV white spaces, and has developed stationary prototypes based on the standards. Although future TV white-space utilization by portable devices will contribute to the further effective use of frequency resources, it is difficult to miniaturize components and circuits for portable devices due to its lower operational frequency than existing WiFi or cellular bands and its relatively wide frequency range of 470-710 MHz. In addition, technology to avoid interference with TV broadcasts is necessary to be implemented in portable devices. On the other hand, propagation characteristic evaluation supposing practical operation is required for the feasibility study on TV white-space utilization.

Achievement

NICT developed the world's first portable-size Android tablet terminal that enables radio communication in TV bands. This tablet terminal is originally based on an off-the-shelf terminal and a frequency converter newly developed by NICT is implemented for utilizing TV white spaces. Radio communication in both TV and 2.4 GHz bands is available with an original WLAN system (IEEE802.11b/g) and Internet access is also possible through the white-space WLAN base station developed by NICT. In addition, this tablet terminal can operate in the frequency considered not to interfere with TV broadcasts according to calculation results provided by the white-space database developed by NICT, and can automatically select the optimal frequency according to data traffic, etc. through control by the network manager.

Some other functions are implemented in this tablet terminal as below.

1. A function to display the white-space availability of each channel and the terminal location on a map by acquiring information on primary users (TV broadcasters) from the white-space database.

2. A power control function for the different limitation of output power according to white-space status such as a location and time.

Future prospects

Mobile communication in TV white spaces has many subjects. For example, a white-space judging method for avoiding interference with TV broadcasts is required. NICT will evaluate the propagation characteristic using this tablet terminal and offer the information that contributes to a technical reference and a rule designed for TV white-space operation. Furthermore, NICT continues to the standardization activities of wireless communication systems utilizing TV white spaces and promotes the development of portable devices based on such standardized communication systems by applying elemental technologies implemented in this tablet terminal.