(communications) Assignment of available frequencies in the radio spectrum to specific stations and for specific purposes, to give maximum utilization of frequencies with minimum interference between stations.
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(communications) Assignment of available frequencies in the radio spectrum to specific stations and for specific purposes, to give maximum utilization of frequencies with minimum interference between stations.
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The radio frequency (RF) electromagnetic spectrum is an aspect of the physical world which, like land, water, and air, is subject to usage limitations. 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 standardisation.
A number of forums and standards bodies work on standards for frequency allocation, including:
High-demand sections of the electromagnetic spectrum may sometimes be allocated through auctions.
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A person may use the following, which all use slices of the radio spectrum that are typically arbitrated at the national level, although typical users will be unable to identify the radio bands or modulation used:
Note that power levels vary widely (from 1mWatt in a bluetooth node to 1000 Watts in a microwave oven). Note that while the general RF band (ie wavelength, ie, frequency) controls propagation characteristics, the detailed particulars of "who uses what" is completely arbitrary and historical. Some particular frequency will require line-of-sight, or is attenuated by rain; but whether it carries ambulance or pizza delivery traffic completely depends on where you live.
Note also that earlier equipment could not process higher frequencies, nor was it compact enough to support certain uses. Over time the exploitable frequencies have increased and semiconductors have shrunk. A tube radio is neither mobile nor reasonably battery powered; GPS works at 1,500 Mhz and fits in your pocket. You might use a bluetooth headset to talk to your GSM phone which is trunked on a microwave link, and at the other end someone is on a cordless phone.
The range of "radio frequencies" is a matter of international convention. The separation of countries into the three formal ITU RF allocation regions is the source of different RF allocation among continents. The definition of the ITU Regions (capital R, for ITU-R Regions) is based largely on longitude. According to ITU Radio Regulations (RR) section 5.1: Member States assign licences to stations and Article 5 of the ITU RR allocates frequencies to services (such as Broadcasting and Mobile). The ITU divides the world into five administrative regions:
The ITU also categorises states into three Radio regulatory Regions:
So, at the very least the RF allocations fundamentally differ between Continents. Longitude may traverse continents, for example, Meridian E401 crosses Europe (Russia), Asia (Middle East) and Africa. The separation may echo the 'Euro-sphere' (including Africa, Middle East and Russia) as Region 1, the American continent as Region 2, and Asia as Region 3.
The division between Europe and the 'other regions' is the root of the different RF allocations in the ITU Radio Regulations, and standards around the world. Based mainly on George A. Codding, Dr. Haim Mazar [1] (vice chairman of ITU-R Study group 1 [2])details how and why there are three separate Regions. Through the efforts of the ITU and its predecessor, the International Radio Telegraph Union, most of the usable part of the spectrum has been divided among various radio services (Codding 1959:80). These are the phases of the longitude separation into three ITU Regions:
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