|
Use of radio frequency bands of the electromagnetic spectrum is regulated by governments in most countries, in a Spectrum management process known as frequency allocation or spectrum allocation. Radio propagation does not stop at national boundaries. Giving technical and economic reasons, governments have sought to harmonise the allocation of RF bands and their standardization. A number standards bodies work on standards for frequency allocation, including: * International Telecommunication Union (ITU) * European Conference of Postal and Telecommunications Administrations (CEPT) * Inter-American Telecommunication Commission (CITEL) These standards bodies have assigned frequency bands in three types of allocation: * No one may transmit: frequencies reserved for radio astronomy to avoid interference at radio telescopes * Anyone may transmit, as long as they respect certain transmission power and other limits: open spectrum bands such as the unlicensed ISM bands and the unlicensed ultra-wideband band. * Only the licensed user of that band may transmit: the licensing body may give the same frequency or band to several users as a form of frequency reuse if they cannot interfere because their coverage map areas never overlap. Amateur radio frequency allocations also devoted only for licensed users with "listen before talk" contention-based protocol. Sections of the electromagnetic spectrum that are in high demand are usually allocated through auctions. ==Daily impact== Every day, users rely on allocation of frequencies for efficient use of such devices as: * cell phone * cordless phone * garage door opener * car key remote control * broadcast television and audio * Standard time broadcast * vehicle-speed radar, air traffic radar, weather radar * mobile radio * Global Positioning System (GPS) navigation * satellite TV broadcast reception; also backend signal dissemination * Microwave oven * Bluetooth * Wifi * Zigbee * RFID devices such as active badges, passports, wireless gasoline token, no-contact credit-cards, and product tags * toll-road payment vehicle transponders * Citizen's band radio and Family Radio Service * Radio control, including Radio-controlled model aircraft and vehicles * wireless microphones and musical instrument links 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「frequency allocation」の詳細全文を読む スポンサード リンク
|