IEEE 802.22, is a standard for wireless regional area network (WRAN) using white spaces in the television (TV) frequency spectrum.
[1] The development of the IEEE 802.22 WRAN standard is aimed at using cognitive radio (CR) techniques to allow sharing of geographically unused spectrum allocated to the television broadcast service, on a non-interfering basis, to bring broadband access to hard-to-reach, low population density areas, typical of rural environments, and is therefore timely and has the potential for a wide applicability worldwide.
[2] It is the first worldwide effort to define a standardized air interface based on CR techniques for the opportunistic use of TV bands on a non-interfering basis.
In response to a notice of proposed rulemaking (NPRM) issued by the U.S. Federal Communications Commission (FCC) in May 2004, the IEEE 802.22 working group on Wireless Regional Area Networks was formed in October 2004.
[4] Its project, formally called as Standard for Wireless Regional Area 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 focused on constructing a consistent, national fixed point-to-multipoint WRAN that will use UHF/VHF TV bands between 54 and 862 MHz.
The Institute of Electrical and Electronics Engineers (IEEE), together with the FCC, pursued a centralized approach for available spectrum discovery.
Devices which would operate in the TV white space band (TVWS) would be mainly of two types: Fixed and Personal/Portable.
Fixed devices also communicate with the central database to identify other transmitters in the area operating in TVWS.
The BS, with the information gathered, will evaluate whether a change is necessary in the channel used, or on the contrary, if it should stay transmitting and receiving in the same one.
When a CPE is turned on, it will sense the spectrum, find out which channels are available and will receive all the needed information to attach to the BS.
Such periodic interruption of data transmission could impair the QoS of cognitive radio systems.
This issue is addressed by an alternative operation mode proposed in IEEE 802.22 called Dynamic frequency hopping (DFH)[5] where data transmission of the WRAN systems are performed in parallel with spectrum sensing without any interruption.