White-Space Spectrum Shows Potential for Long-Range Communications

The TV white-space spectrum has proven that it can increase broadband-communication services in difficult areas. Yet it has not been fully vetted for long-range communications. When an unlicensed portion of radio spectrum with a low probability of interference is used on existing infrastructures, the lower frequency (470 to 710 MHz in Japan) typically has a low impact on distance decay (compared to higher-frequency legacy systems). Recently, a long-range broadband-communications field trial in Japan’s TV white space was completed using IEEE 802.22- and 802.11af-based systems.

The IEEE 802.22 standard for wireless regional-area networks (WRANs) covers a radius of 10 to 40 km for rural-area broadband service. The IEEE 802.11af standard, in contrast, specifically targets white-space operation. In this demonstration, a multihop network was constructed using an IEEE 802.22 backbone link. That link was connected to an IEEE 802.11af wireless link, thereby expanding the connection area. The multihop configuration uses a relay terminal to connect terminals that cannot directly transmit on their own. A wireless local-area network (WLAN), based on conventional IEEE 802.11b/g/n in the 2.4-GHz band, was attached to the IEEE 802.11af link. It allowed off-the-shelf devices to access the network’s connection.