Over-the-air broadcast TV channels are separated by unused frequencies. This “white space” in the broadcast spectrum varies with the channels present in a locale and creates opportunities for other applications.
As a step in putting these unused channels to practical use, the IEEE has started work on a standard to enable the deployment of wireless regional area networks using the unused TV channels, while not interfering with the licensed services now operating in the TV bands.
The new project, IEEE P802.22, ‘Standard for Wireless RegionalArea Networks (WRAN) -Specific requirements – Part 22: Cognitive Wireless RAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications: Policies and procedures for operation in the TV Bands,’ will specify a cognitive air interface for fixed, point-to-multipoint, wireless regional area networks that operate on unused channels in the VHF/UHF TV bands between 54 and 862 MHz.
‘Signals at these frequencies can propagate 40 km or more from a well-sited base station, depending on terrain,’ said Carl R. Stevenson, Interim Chair of the IEEE P802.22 Working Group.
‘This is ideal spectrum for deploying regional networks to provide broadband service in sparsely populated areas, where vacant channels are available. Our goal is to equal or exceed the quality of DSL or cable modem services, and to be able to provide that service in areas where wireline service is economically infeasible, due to the distance between potential users.’
‘This standard will enable the creation of interoperable IEEE 802 WRAN products. It has generated a great deal of interest from wireless internet service providers, community networking organisations, government bodies and other parties.’
Protocols in the standard will ensure that this new service does not cause harmful interference to the licensed incumbent services in the TV broadcast bands. The standard will provide for broadband systems that choose portions of the spectrum by sensing what frequencies are unoccupied.
In the US, The Federal Communication Commission has issued a Notice of Proposed Rule Making to open the 54-698 MHz portion of the TV spectrum for unlicensed usage. IEEE 802.22 will enable compliance to these rules once they are finalised.
‘The standard, which will work with existing IEEE 802 architectures, will give IEEE 802.11 wireless local area networks in outlying areas a fatter pipe for receiving and transmitting data,’ says Stevenson.
‘It also will complement IEEE 802.16 metropolitan area networks, which do not include cognitive radio functions for sharing TV spectrum.’
‘The concepts underlying this standard are attractive to both developed and undeveloped countries having little wireline infrastructure. By extending out to 40km or more, most regional area networks should have enough potential subscribers within their coverage areas to make them viable ventures.’
The formation of the IEEE 802.22 Working Group has involved broad participation from those in the TV broadcast sector and the public safety community who are licensed users of the target spectrum, as well as from chip vendors, wireless equipment suppliers, and even other countries having large, relatively sparsely populated areas.