AchievementsThe developed prototype is the world's first WiFi system in TVWS based on the IEEE 802.11af draft standard. It verifies the physical (PHY) and medium access control (MAC) layer design of the draft specification. One of the OFDM PHY modes that take a single 6 MHz TV channel to operate is implemented with transmission power of 20 dBm. The prototype has an interface and co-worked with White Space Data Base (WSDB) developed by NICT and the full MAC specification of the secured protocol is implemented for primary user (licensed TV broadcaster) protections. The prototype also has an interface and co-works with the Registered Location Secure Server (RLSS) that is defined in the 802.11af draft standard to avoid interference with other white space users (secondary users). NICT has developed the RLSS server. It is approved that the primary users and secondary users operating in the co-channels can be sufficiently protected.
Future prospectsThere are many benefits of 802.11af systems compared with other current WiFi technologies. Firstly, in view of the fact that 802.11af systems operating the TVWS use frequencies below 1 GHz, it would allow for much longer distances to be achieved. Current WiFi systems use frequencies in the ISM bands -- the lowest band is 2.4 GHz and the signals are easily absorbed. Secondly, by operating in the TVWS, the usable spectrum is much broader than that of ISM bands when efficiently aggregated. Looking at these benefits, it is widely believed that 802.11af systems offer sufficient advantages to enable a broad market.
With the evolution of regulations regarding the TVWS worldwide, it is expected IEEE 802.11af may adapt to those regulation updates and complete the standard by 2014. We are now working on the next revision to implement the full PHY specification and new features come along with the regulatory updates. We are also looking for the opportunities for technical transfer.