Wireless communication in TV white space succeeded

－ By using database to provide available channels, enabling traffic off-load －

June 7, 2012

The National Institute of Information and Communications Technology (NICT, President: Dr. Hideo Miyahara) has succeeded in wireless communication in the TV broadcast band (470MHz-710MHz) where its operational channels are set to radio equipments according to calculation results provided from the white space database. Efficient wireless communication environment to accommodate increasing mobile traffic is expected, which consequently loads off traffic of wireless networks where current throughput is not sufficiently achieved due to traffic congestion and radio interference.

Background

In order to address issues which have arisen as a consequence of exhaustive frequency assignments as a result of expanding broadband wireless communications, wireless communication in “the white space” is expected in the world. In the white space, wireless communication systems (secondary systems) share frequency with existing wireless systems (primary systems) and operate in frequency bands with no harmful interference to the primary systems. Radio regulatory authorities such as FCC and Ofcom are considering secondary utilization of the TV band as the white space by adopting white space database to obtain available frequency lists for the secondary systems. In Japan, the committee on white space promotion under the Ministry of Internal Affairs and Communications has reported, in January 2012, that communication systems are expected to share spectrum with existing TV broadcast stations. However, practical feasibility on white space database utilization for white space communications has not been investigated with real systems.

Achievements

White Space Database

NICT has developed “white space database” which provides a channel list usable for the secondary systems by calculating the interference level between the primary systems and the secondary systems, and white space base station which requests the white space database for available channels and reconfigure itself for operation in the white space. Furthermore, NICT has integrated the white space database and the base station and confirmed successful wireless communications in the TV broadcasting band (470MHz-710MHz) with no interference to the primary system (TV broadcasting) by selecting available channels automatically.

The white space base station has a function to interconnect the base stations each other in a wide area to expand the wireless communication infrastructure using the mesh network technology.

Future prospects

NICT plans to evaluate its original white space calculation methods according to the topographical features of Japan and mobile system utilization. NICT will promote its technology transfer as well as international standardization activities and development of small-sized equipments with less power consumption to ensure commercialization of the research results.

Appendix

1. Developed equipments

White Space Database

The developed white space database (WSDB) provides available channels in TV white space to white space base station (WSBS) by responding to WSBS’s query. The interface between existing TV broadcasting and the secondary system is automatically calculated and available channels at each WSBS location are derived. The WSDB is equipped with web interface as shown in Fig. 1. The WSDB can implement multiple calculation methodｓ and switch between them.

Fig. 1： Screenshot of management interface of the white space database

Left:

Circles in red are TV broadcasting service area calculated according to the FCC rule

Right:

List of available channels in a specified location (Yokosuka) with a specified antenna height

Fig. 2： White Space Base Station

White Space Base Station

Prototype of the white space base station (WSBS) is shown in Fig. 2. The RF modules installed in the WSBS are reconfigurable and are able to operate on 470-710MHz with output power 100mW. WSBS has a function of wireless router by which terminals equipped with wireless LAN can connect the Internet via the WSBS.

2. Demonstration system

Network architecture of the demonstration system is shown in Fig. 3. The WSBS can organize a mesh network either by wireless LAN in 2.4GHz or the reconfigurable RF unit in white space. The WSBS cannot operate in white space until it is approved by the WSDB.

In the demonstration, the WSBS first organize a mesh network in 2.4GHz ISM band, then all the WSBSs access the WSDB and obtain the available channels. Obtained available channels are reported to the mesh manager and the mesh manager determines a frequency channel to operate. The determined channel is suggested to all the WSBSs to start their operations in the channel.

Figure 3： Network architecture of the demonstration system

Acknowledgement:
This research was conducted under a contract of R&D for radio resource enhancement, organized by the Ministry of Internal Affairs and Communications, Japan.