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IEEE 802.22, is a standard for wireless regional area network (WRAN) using white spaces in the television (TV) frequency spectrum.〔(【引用サイトリンク】title=IEEE 802 LAN/MAN Standards Committee 802.22 WG on WRANs (Wireless Regional Area Networks) )〕 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. 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. IEEE 802.22 WRANs are designed to operate in the TV broadcast bands while assuring that no harmful interference is caused to the incumbent operation: digital TV and analog TV broadcasting, and low power licensed devices such as wireless microphones. The standard was expected to be finalized in Q1 2010, but was finally published in July 2011. IEEE P802.22.1 is a related standard being developed to enhance harmful interference protection for low power licensed devices operating in TV Broadcast Bands. IEEE P802.22.2 is a recommended practice for the installation and deployment of IEEE 802.22 Systems.〔 IEEE 802.22 WG is a working group of IEEE 802 LAN/MAN standards committee which was chartered to write the 802.22 standard. The two 802.22 task groups (TG1 and TG2) are writing 802.22.1 and 802.22.2 respectively. ==Technology== 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. 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. Specific TV channels as well as the guard bands of these channels are planned to be used for communication in IEEE 802.22. The Institute of Electrical and Electronics Engineers (IEEE), together with the FCC, pursued a centralized approach for available spectrum discovery. Specifically each base station (BS) would be armed with a GPS receiver which would allow its position to be reported. This information would be sent back to centralized servers (in the USA these would be managed by the FCC), which would respond with the information about available free TV channels and guard bands in the area of the BS. Other proposals would allow local spectrum sensing only, where the BS would decide by itself which channels are available for communication. A combination of these two approaches is also envisioned. Devices which would operate in the TV white space band (TVWS) would be mainly of two types: Fixed and Personal/Portable. Fixed devices would have geolocation capability with an embedded GPS device. Fixed devices also communicate with the central database to identify other transmitters in the area operating in TVWS. Other measures suggested by the FCC and IEEE to avoid interference include dynamic spectrum sensing and dynamic power control. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「IEEE 802.22」の詳細全文を読む スポンサード リンク
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