Frequency Allocation

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 of forums and standards bodies work on standards for frequency allocation, including:

• International Telecommunication Union (ITU)
• European Conference of Postal and Telecommunications Administrations (CEPT)
• European Telecommunications Standards Institute (ETSI)
• International Special Committee on Radio Interference (Comité international spécial des perturbations radioélectriques - CISPR)

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, and the somewhat more regulated amateur radio frequency allocations. Often users use a "listen before talk" contention based protocol.
• Only the licensed user of that band may transmit: the licensing body may give the same frequency to several users as a form of frequency reuse if they cannot interfere because their coverage map areas never overlap.

High-demand sections of the electromagnetic spectrum may sometimes be allocated through auctions.